Dissertations / Theses: 'Microwave imaging. Antenna arrays'

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Radzicki, Vincent R. "FMCW Subsurface Microwave Imaging with Hexagonal Antenna Arrays." International Foundation for Telemetering, 2014. http://hdl.handle.net/10150/578169.

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ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA Ground-penetrating radar (GPR) imaging is typically conducted in the pulse-echo mono-static format with a simple CW pulse as the probing signal. Recently, the data-acquisition hardware has been extended to the use of linear multi-element arrays. This paper presents an advanced GPR imaging system with FMCW probing waveforms, with a seven-element hexagonal array and software-defined data-acquisition hardware. The use of FMCW probing signals is for the optimization of the information contents of the returned waveforms. The utilization of the hexagonal unit is to produce sub-images with direction-independent resolution capability. In this paper, mathematical analysis, system modeling, field experiments, and image reconstruction are included to illustrate the performance and capability of the engineering concepts.

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Curry, Mark A. "Techniques for radar imaging using a wideband adaptive array /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5841.

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Bashri, Mohd Saiful Riza. "Wearable devices for microwave head diagnostic systems." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33243.

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Although current head imaging technologies such as magnetic resonance imaging (MRI) and computed tomography (CT) are capable of providing accurate diagnosis of brain injuries such as stroke and brain tumour, they have several limitations including high cost, long scanning time, bulky and mostly stationary. On the other hand, radar-based microwave imaging technology can offer a low cost, non-invasive and non-ionisation method to complement these existing imaging techniques. Moreover, a compact and wearable device for microwave head imaging is required to facilitate frequent or real-time monitoring of a patient by providing more comfort to the patient. Therefore, a wearable head imaging device would be a significant advantage compared to the existing wideband microwave head sensing devices which typically utilise rigid antenna structure. Furthermore, the wearable device can be integrated into different microwave imaging setups such as real-time wearable head imaging systems, portable systems and conventional stationary imaging tools for use in hospitals and clinics. This thesis presents the design and development of wearable devices utilising flexible antenna arrays and compact radio frequency (RF) switching circuits for wideband microwave head imaging applications. The design and characterisation of sensing antennas using flexible materials for the wearable head imaging device are presented in the first stage of this study. There are two main variations of monopole antennas that have been developed in this research, namely trapezoidal and elliptical configurations. The antennas have been fabricated using different flexible substrate materials such as flexible FR-4, polyethylene terephthalate (PET) and textile. Wideband performances of the antennas have been achieved by optimising their co-planar waveguide feeding line structures. Importantly, the efficiencies of the fabricated antennas have been tested using a realistic human head phantom by evaluating their impedance matching performances when operating in close proximity to the head phantom. The second stage of the study presents the development of wearable antenna arrays using the proposed flexible antennas. The first prototype has been built using an array of 12 flexible antennas and a conformal absorbing material backed with a conductive sheet to suppress the back lobe radiation of the monopole antennas. Additionally, the absorber also acts as a mounting base to hold the antennas where the wearable device can be comfortably worn like a hat during the measurement and monitoring processes. The effect of mutual coupling between adjacent antennas in the array has been investigated and optimised. However, the use of the absorbing material makes the device slightly rigid where it can only be fitted on a specific head size. Thus, a second prototype has been developed by using a head band to realise a stretchable configuration that can be mounted on different sizes of human heads. Furthermore, due to the stretchable characteristic of the prototype, the antennas can be firmly held in their positions when measurements are made. In addition, fully textile based sensing antennas are employed in this prototype making it perfectly suitable for monitoring purposes. Low cost and compact switching circuits to provide switching mechanism for the wearable antenna array are presented in the third stage of this study. The switching circuit is integrated with the antenna array to form a novel wearable microwave head imaging device eliminating the use of external bulky switching network. The switching circuit has been built using off-the-shelf components where it can be controlled wirelessly over Bluetooth connection. Then, a new integrated switching circuit prototype has been fabricated using 6-layer printed circuit board (PCB) technology. For the purpose of impedance matching for the radio-frequency (RF) routing lines on the circuit, a wideband Microstrip-to-Microstrip transition is utilised. The final stage of this study investigates the efficacy and sensitivity of the proposed wearable devices by performing experiments on developed realistic human head phantoms. Initially, a human head phantom has been fabricated using food-based ingredients such as tap water, sugar, salt, and agar. Subsequently, lamb's brains have been used to improve the head phantom employed in the experiments to better mimic the heterogeneous human brain. In terms of imaging process, an interpolation technique developed using experimental data has been proposed to assist the localisation of a haemorrhage stroke location using the confocal delay-and-sum algorithm. This new technique is able to provide sensible accuracy of the location of the blood clot inside the brain. The wearable antenna arrays using flexible antennas and their integrations with compact and low cost switching circuits reported in this thesis make valuable contribution to microwave head imaging field. It is expected that a low-cost, compact and wearable radar-based microwave head imaging can be fully realised in the future for wide range of applications including static scanning setup in hospitals, portable equipment in ambulances and as a standalone wearable head monitoring system for remote and real-time monitoring purposes.

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Qassim, K. A. S. "Optimisation of focal plane arrays for microwave imaging : printed Yagi, dielectric rod and constant width slot antennas are investigated and optimised for close stacking in focal plane arrays intended for microwave imaging." Thesis, University of Bradford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320761.

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Alonso, del Pino María. "Terahertz integrated antenna arrays for imaging applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/130010.

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Terahertz is the portion of the spectrum that covers a frequency range between 300 GHz - 3 THz. This frequency band has proven its potential for imaging applications thanks to the good compromise between spatial resolution and penetration; however, this push towards high frequencies contains many technological difficulties in all the subsystems involved in the signal generation, transmission and detection. The power budget restrictions and high losses that sources and receivers currently suffer at these frequencies require systems with a high level of integration among all the devices and components of the systems and subsystems. Therefore, the antennas needed for these systems require to be integrated within the same fabrication processes and technologies as the sensing and power converting devices that are used at their terminals. This doctoral thesis has focused on the development of integrated antenna arrays at Terahertz frequencies for imaging applications, for both near-field and focal-plane geometries, with a special emphasis on the technologies and the fabrication capabilities that can be potentially used and are currently available. The current imaging systems require large arrays of antennas in order to achieve the high-speed image acquisition that is required in most THz applications. This fact increases considerably the difficulty and complexity to achieve highly integrated and efficient antennas. This thesis has characterized and analyzed these difficulties and provided solutions to the development of antenna arrays at millimeter and submillimeter wave frequencies. The first part of this thesis has focused on the study of a planar antenna array, called retina, for a specific near-field imaging system based on the Modulated Scatterer Technique (MST) at millimeter and submillimeter-wave frequencies. This system has been selected for its capabilities to perform high-speed imaging and because it does not require a high frequency distribution line network. However, it is hindered by many technological difficulties: the selection of an antenna geometry that achieves high efficiency, the selection of the adequate active element and its integration with the antenna. In this thesis, these challenges have been addressed and studied in-depth, and a design methodology that integrates all the different aspects of the system has been developed. Because planar antennas at millimeter and submillimeter wave frequencies suffer from high losses due to the surface wave modes inside substrate, these losses have been analyzed and quantified for different antennas, and an antenna geometry that reduces significantly this problem has been developed. Different switching technologies currently or potentially available at these high frequencies have been considered in order to study and analyze their capabilities and their integration possibilities: PIN diodes, Schottky diodes and RF-MEMS. These technologies have been studied through the development of three retina prototypes, which have been fabricated using high precision fabrication processes such as laser micromachining and photolithographic. Different measurement set ups were fabricated and assembled to validate the different premises presented. The second part of the thesis is devoted to the study of integrated Focal Plane Arrays (FPA). The development of FPA at submillimeter wave frequencies is highly on demand due to the enormous progress in designing integrated heterodyne receivers. These receivers integrate arrays of submillimeter-wave diode-based mixers and multipliers with Monolithically Integrated Circuit (MIC) amplifiers on the same wafer stack. For this stackable multi-pixel terahertz camera technology to work, a leaky wave antenna with silicon micro-lenses has been developed, which allows wafer level integration compatible with silicon micro-fabrication techniques for bulk array manufacturing and has high directivity in order to illuminate a reflector efficiently. Detailed and thorough design guidelines for this antenna are presented. Two antenna prototypes were built in order to evaluate the two fabrication possibilities: advanced laser micro-fabrication and photolithographic fabrication. A study of the aberrations of the lens has been developed in order to evaluate the performance of the lens profile fabricated. Moreover, a set of radiation pattern measurements of the fabricated prototypes was performed in order to evaluate the performance of the antenna and its possibilities to be used as a FPA.

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Guo, Yong Rutledge David B. Rutledge David B. "Millimeter-wave integrated-circuit horn-antenna imaging arrays /." Diss., Pasadena, Calif. : California Institute of Technology, 1992. http://resolver.caltech.edu/CaltechETD:etd-07242007-092924.

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Zhang, Haoyu. "Microwave imaging for ultra-wideband antenna based cancer detection." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/9958.

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Breast cancer is one of the most widespread types of cancer in the world. The key factor in treatment is to reliably diagnose the cancer in the early stages. Moreover, currently used clinical diagnostic methods, such as X-ray, ultra-sound and MRI, are limited by cost and reliability issues. These limitations have motivated researchers to develop a more effective, low-cost diagnostic method and involving lower ionization for cancer detection. In this thesis, radar based microwave imaging is proposed as a method for early breast cancer detection. This imaging system has advantages such as low cost, being non- invasive and easy to use, with high image resolution and its thus good potential for early cancer detection. In the first stage, an ultra-wideband Vivaldi antenna and a slot Vivaldi antenna are proposed, simulated and fabricated for breast cancer detection. The designed antennas exhibit an ultra-wideband working frequency. The radiation patterns also achieve the desired directional radiation patterns. The second stage of this study presents a planar breast phantom and a hemisphere breast phantom. These two breast phantoms are simulated and fabricated using CST microwave studio and tissue-mimicking materials respectively. Mono-static radar systems based on a single antenna configuration and an antenna pair configuration are then proposed. These two systems are used to measure the planar breast phantom and hemi- sphere breast phantom, with the scattering signals measured in the frequency and time domains. Based on the measurement results, it is concluded that the reflected energy increases when the antenna moves close to the tumour; otherwise, the reflected energy is reduced when the antenna moves away from the tumour. The received time domain scattering signals are processed first and then used to create microwave images to indicate tumour position. A clutter removal method is proposed to extract the tumour response from the received signals. The microwave images are then created using the tumour response based on the simulation and experimental results. The imaging results indicate that a 5 mm radius tumour can be detected. The tumour burial depth is also studied. A multi bio- layer phantom which contains deep and shallow buried tumours is simulated and measured using the Vivaldi antenna. A spectrum analysis method is proposed to distinguish between different tumour depths. The results indicate that a difference in depth of 15 mm results in a mean change of 0.3 dB in the magnitude of the spectrum. Discrimination between benign and malignant tumours is also considered in this study. The singularity expansion method (SEM) for breast cancer is proposed to discriminate between benign and malignant tumours based on their morphology. Two cancerous breast phantoms are developed in CST. The benign tumour is a 5mm radius sphere and the malignant tumour is a spiny sphere with an average radius of 5mm. The use of the SEM leads to the successful discrimination of these two tumours. This method provides a solution to discriminate between benign and malignant tumours similar size when the resulting images cannot provide sufficient resolution. A preliminary study of brain cancer detection is also concluded. Research in this area has never been implemented. A cancerous brain model is designed and simulated in CST. The antenna pair configuration is then used to measure the cancerous brain, with the scattering signals measured. Microwave images for brain cancer detection are then created based on the measurement results. The tumour is correctly indicated in the resulting images.

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Ozdemir, Caner. "Synthetic aperture radar algorithms for imaging antenna-platform scattering /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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Janice, Brian A. "Differential Near Field Holography for Small Antenna Arrays." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/999.

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"Near-field diagnosis of antenna arrays is often done using microwave holography; however, the technique of near-field to near-field back-propagation quickly loses its accuracy with measurements taken farther than one wavelength from the aperture. The loss of accuracy is partially due to windowing, but may also be attributed to the decay of evanescent modes responsible for the fine distribution of the fields close to the array. In an effort to achieve better resolution, the difference between these two phase-synchronized near-field measurements is used and propagated back. The performance of such a method is established for different conditions; the extension of this technique to the calibration of small antenna arrays is also discussed. The method is based on the idea of differential backpropagation using the measured/simulated/analytical data in the near field. After completing the corresponding literature search authors have found that the same idea was first proposed by P. L. Ransom and R. Mittra in 1971, at that point with the Univ. of Illinois. This method is basically the same, but it includes a few distinct features: 1. The near field of a (faulty) array under test is measured at via a near field antenna range. 2. The template (non-faulty) near field of an array is simulated numerically (full-wave FDTD solver or FEM Ansoft/ANSYS HFSS solver) at the same distance - an alternative is to use measurements for a non-faulty array. 3. Both fields are assumed (or made) to be coherent (synchronized in phase). 4. A difference between two fields is formed and is then propagated back to array surface using the angular spectrum method (inverse Fourier propagator). The corresponding result is the surface (aperture) error field. This approach is more precise than the inverse Rayleigh formula used in Ransom and Mittra's paper since the evanescent spectrum may be included into consideration. 5. The error field magnitude peaks at faulty elements (both amplitude and phase excitation fault). 6. The method inherently includes all mutual coupling effects since both the template field and the measured field are full-wave results."

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Zhang, Tieren, University of Western Sydney, of Science Technology and Environment College, and School of Engineering and Industrial Design. "Applications of microwave holography to the assessment of antennas and antenna arrays." THESIS_CSTE_EID_Zhang_T.xml, 2001. http://handle.uws.edu.au:8081/1959.7/770.

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Gabor's original holography, which is the basic theory of modern microwave holographic techniques, is introduced. By computer simulations, it is demonstrated that the conventional holographic approach can be used as a tool to reconstruct aperture field distributions of an antenna with some constraints. Computer simulations of the theory and technique of the improved microwave holographic approach originally introduced by Rahmat-Samii et al. are carried out. The results show that it can be used for surface distortion diagnosis of large reflector antennas. The physical optics integral formulation is derived by general solutions of the vector wave equations. The necessary theory , which is needed to reconstruct the aperture field from near-field measurements both in a rectangular coordinate system and in a cylindrical coordinate system is developed. It is based on the plane wave spectrum and the vector wave modal expansion of an electromagnetic field. By using a simple dipole and other well-defined antennas, computer simulations have been performed. The results show that the technique is rigorous and applicable. It is also demonstrated that the sampling intervals and the number of sampling points should be chosen carefully in order to obtain a satisfactory resolution of the reconstructed aperture field. Furthermore, the simulations carried out in this work reveal that the real aperture field distribution of a dipole antenna has a maximum point at each end of the antenna. This characteristic can only be obtained at a very close distance to the antenna. This study also reveals the significant contributions of the evanescent waves to the aperture reconstruction. A simple but effective method for examining the evanescent waves from the measured near-field is also presented. By using dipoles and other well known antennas and antenna arrays, the experiments were carried out. The experimental results provide reasonable good agreements with the simulations. The technique proposed is effective and accurate. Doctor of Philosophy (PhD)

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Zhang, Tieren. "Applications of microwave holography to the assessment of antennas and antenna arrays." View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20040330.103805/index.html.

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Thesis (Ph.D.) -- University of Western Sydney, 2001. "Submitted in fulfilment of requirements for the degree of Doctor of Philosophy, School of Engineering and Industrial Design, University of Western Sydney" Includes bibliography.

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Guardiola, Garcia Marta. "Multi-antenna multi-frequency microwave imaging systems for biomedical applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134967.

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Medical imaging refers to several different technologies that are used to view the human body in order to diagnose, monitor, or treat medical conditions. Each type of technology gives different information about the area of the body being studied depending on the radiation used to illuminate de body. Nowadays there are still several lesions that cannot be detected with the current methods in a curable stage of the disease. Moreover they present some drawbacks that limit its use, such as health risk, high price, patient discomfort, etc. In the last decades, active microwave imaging systems are being considered for the internal inspection of light-opaque materials thanks to its capacity to penetrate and differentiate their constituents based on the contrast in dielectric properties with a sub-centimeter resolution. Moreover, they are safe, relatively low-cost and portable. Driven by the promising precedents of microwaves in other fields, an active electromagnetic research branch was focused to medical microwave imaging. The potential in breast cancer detection, or even in the more challenging brain stroke detection application, were recently identified. Both applications will be treated in this Thesis. Intensive research in tomographic methods is now devoted to develop quantitative iterative algorithms based on optimizing schemes. These algorithms face a number of problems when dealing with experimental data due to noise, multi-path or modeling inaccuracies. Primarily focused in robustness, the tomographic algorithm developed and assessed in this thesis proposes a non-iterative and non-quantitative implementation based on a modified Born method. Taking as a reference the efficient, real-time and robust 2D circular tomographic method developed in our department in the late 80s, this thesis proposes a novel implementation providing an update to the current state-of-the-art. The two main contributions of this work are the 3D formulation and the multi-frequency extension, leading to the so-called Magnitude Combined (MC) Tomographic algorithm. First of all, 2D algorithms were only applicable to the reconstruction of objects that can be assumed uniform in the third dimension, such as forearms. For the rest of the cases, a 3D algorithm was required. Secondly, multi-frequency information tends to stabilize the reconstruction removing the frequency selective artifacts while maintaining the resolution of the higher frequency of the band. This thesis covers the formulation of the MC tomographic algorithm and its assessment with medically relevant scenarios in the framework of breast cancer and brain stroke detection. In the numerical validation, realistic models from magnetic resonances performed to real patients have been used. These models are currently the most realistic ones available to the scientific community. Special attention is devoted to the experimental validation, which constitutes the main challenge of the microwave imaging systems. For this reason, breast phantoms using mixtures of chemicals to mimic the dielectric properties of real tissues have been manufactured and an acquisition system to measure these phantoms has been created. The results show that the proposed algorithm is able to provide robust images of medically realistic scenarios and detect a malignant breast lesion and a brain hemorrhage, both at an initial stage.

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Moussounda, Renaud. "Analysis and Design of Coupled-Oscillator Arrays for Microwave Systems." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1388354578.

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Petrović, Nikola. "Measurement System for Microwave Imaging Towards a Biomedical Application." Doctoral thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-24878.

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Microwave imaging techniques have shown excellent capabilities in various fields such as civil engineering, nondestructive testing, industrial applications, and have in recent decades experienced strong growth as a research topic in biomedical diagnostics. Many research groups throughout the world work on prototype systems for producing images of human tissues in different biomedical applications, particularly breast tumor detection. However, the research community faces many challenges and in order to be competitive to other imaging modalities one of the means is to put emphasis on experimental work. Consequently, the use of flexible and accurate measurement systems, together with the design and fabrication of suitable antennas, are essential to the development of efficient microwave imaging systems. The first part of this thesis focuses on measurement systems for microwave imaging in terms of antenna design and development, robot controlled synthetic array geometries, permittivity measurements, and calibration. The aim was to investigate the feasibility of a flexible system for measuring the fields around an inhomogeneous object and to create quantitative images. Hence, such an aim requires solving of a nonlinear inverse scattering problem, which in turn requires accurate measurements for producing good quality experimental data. The presented solution by design of a flexible measurement system is validated by examination of microwave imaging from experimental data with a breast phantom. The second part of the thesis deals with the research challenges of designing high performance antennas to be placed in direct contact with or in close proximity to the imaged object. The need for novel antenna applicators is envisaged in the framework of the Mamacell measurement system, where the antenna applicators have to be designed and constructed to effectively couple the energy into the imaging object. For this purpose the main constraints and design requirements are a narrow lobe of the antenna, very small near-field effects, and small size. Numerical simulations and modeling shows that the proposed ridged waveguide antenna is capable of fulfilling the design requirements and the performance goals, demonstrating the potential for the future microwave imaging system called Mamacell.

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Alkhafaji, Nasr Nomas Hussein. "UHF and Microwave Phase-Modulated Scattering Array." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4998.

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This dissertation investigates the use an array of active nonlinear elements, with particular emphasis on controlling distortion products generated by nonlinear elements in space rather than using conventional ways such as transmission lines, waveguides, and power dividers and combiners. The nonlinear elements are made of assemblies of antennas and electronic switches, called modulated scatterers (MSs). These so-called MSs elements are utilized in a wide variety of applications such as radio frequency identification (RFID) systems, microwave imaging, Internet-of-Things sensors, etc. However, no research work has been reported in the literature regarding exploiting and controlling several distortion products generated by MSs at the same time according to the best of authors' knowledge. To facilitate controlling distortion products which means suppressing or enhancing distortion products in space, we present a nonlinear array with elements that are MSs instead of conventional antennas. MSs are switched ON-OFF at different times by modulation signals having the same frequency. The time delay of the switching process between array elements represents a relative phase shift difference in the frequency domain. Thus, the presented structure is called the phase-modulated scattering array (PMSA). The PMSA has a similar layout of phased arrays, but it does not have a feeding network and is fed by an external source called the illuminating source. Because our system does not need a feeding network and phase shifters, it is potentially easier to implement with low cost. Two different signals which are the illuminating (incident) and modulation signals interact inside switches to generate a huge number of distortion products due to the nonlinearity of switches and the periodic nature of the presented system. Distortion products then leave the presented PMSA to space again (i.e., scattering distortion products). The PMSA is able to treat distortion products and achieve beamforming functions. The operation mechanism of the PMSA is explained by developing two different mathematical models. Communication signal processing perspectives are the basis of the first mathematical model developed to show the spatial characteristics of distortion products generated by our presented PMSA. Its root is originated from a mathematical model of the widely-used polyphase multipath technique in RF communication circuits. However, the adopted technique is suitable only for communication circuits with a single output and parameters prescribed in advance. Thus, the model is further developed to circumvent all the problems mentioned above and to be able to detect the spatial characteristics of distortion products at any point in space. Static impacts of the measurement environment, real radiation patterns of actual antennas utilized in prototypes, and phase and gain errors among paths have been taken into account as well. In the model, every single scatterer is represented by a single separate path. Furthermore, the modified model is extended to include single, two, and multi tones modulation signals. Simulation results have been obtained before and after the modification for a different number of paths and modulation signals with different tones. Results show that the modified model can quantify spatial characteristics of distortion products at any point in space where specific distortion products are enhanced, and others are canceled. Because distortion products are independent in their nature (i.e., each single distortion product has different frequency and phase), they have independent radiation patterns (scattered beams). Therefore, the second mathematical model based on phased antenna array perspectives is developed. The relationship between the two models states that a distortion product which is enhanced at a certain point in space has a maximum scattered beam at that point. Also, the second mathematical model being similar to mathematical models of phased arrays considers effects of all distortion products resulting from single, two, and multi tones modulation signals, and it states that each single distortion component has its particular scattered beam. Next, sub-models for some properties and applications of the presented PMSA such as a diffraction grating-like behavior, nonreciprocity, beamforming, a tool for distortion product analysis of phased arrays and multi-input multi-output (MIMO systems), a reconfigurable-spatial harmonic generator, and a direction finding technique are derived depending on the two main mathematical models. All parts are simulated and results validate all proposed functionalities. Single antennas, antenna arrays, electronic switches (modulators), and a 4-to-8 phase transformer kit using only resistors have been designed, simulated, fabricated, assembled, and tested. Eventually, different structures of the presented PMSAs working at 432MHz and 2.3GHz are tested inside the anechoic chamber. Both frequencies are downconverted to the band 2-22kHz. Modulation signals used in the experimental setups are single and two tones. Data are measured using the commercial software SigView running on a laptop and a spectrum analyzer. Both spatial characteristics and scattered beams of distortion products are measured. Comparisons have been made between measured received responses of scattered signals and theoretical results. They are in good agreement although limitations and challenges are encountered with each round of measurement. Measured results confirm practically that as a number of scatterers increases, more distortion products are controlled at the same time. The distortion product rejection ratio DPRR is more than 15dB for all measured distortion products supposed to be canceled. Directions of scattered beams are found at expected locations with errors less than 3%. Furthermore, directions of illuminating signals or distances separating between PMSA elements are varied to change directions of scattered beams when prescribed values of parameters governing the overall performance are being broken. In other words, the beamforming functionality has been validated practically. Different elements of 8*1-PMSA are turned-off at measurements in order to find fault tolerances of the presented system. Measured results show that when two elements are failed simultaneously, responses can be accepted to some extent.

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Sundaram, Ananth Ramadoss Ramesh. "Electronically Steerable Antenna Array using PCB-based MEMS Phase Shifters." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/SUNDARAM_ANANTH_51.pdf.

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Dey, Abhishek. "Frequency Tunable Antennas and Surface Microwave Imaging System Using Microfluidic Reconfiguration Techniques." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6491.

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Reconfigurable radio frequency (RF) devices are attractive for miniaturization of wireless components and systems by handling functionality of multiple distinct devices. Existing reconfiguration techniques rely on device loadings with semiconductor diodes, ferrite/ferroelectric materials, and microelectromechanical system (MEMS) switches and capacitors. However, it is well-recognized that these techniques cannot fully address important system metrics such as high efficiency, wide frequency tuning range, high power handling capability and cost. Therefore, novel alternative techniques are highly desirable to advance the state of the art in reconfigurable RF devices. The aim of this dissertation is to investigate the novel concept of microfluidically loaded reconfigurability within the context of RF antennas and imaging systems. The proposed devices operate based on continuously movable microfluidic loads consisting of metal (liquid/solid) and dielectric solutions. Microfluidics and microfabrication techniques are utilized with flexible/rigid multilayered substrates to maximize the reconfigurable loading effect on the devices and enable highly reconfigurable antennas and imaging array realizations. Specifically, a wideband frequency tunable monopole antenna is introduced by utilizing continuously movable liquid metal within the microfluidic channel as a length varying conductor. By resorting to ultra-thin channel walls, the liquid metal volume overlapping with the microstrip line feed is utilized as a non-radiating capacitive excitation point to achieve the realized 4:1 (1.29GHz – 5.17GHz) frequency tuning range. Subsequently, an alternative design that replaces liquid metal volume with a microfluidically movable metallized plate is introduced. This novel liquid-metal-free implementation alleviates the liquid metal associated drawbacks of reliability, long-term device operation, and efficiency. The antenna is shown to provide 2:1 (1.6GHz – 3.5GHz) frequency tuning range with > 87 % radiation efficient. Due to the high radiation efficiency, the antenna is also capable of handling 15 W of RF power which is 10 W more than its liquid metal counterpart. This metallized plate approach is also suitable for reconfiguration of miniature antennas, and this is demonstrated with the design/implementation of a microfluidically reconfigurable top loaded monopole antenna. It is also suitable for reconfiguration of other structures such as textile antennas – and this is demonstrated with a 0.8GHz to 1.4GHz frequency reconfigurable textile antenna realization. The last section of the dissertation introduces a novel surface imaging array realization by utilizing the microfluidically reconfigurable metallized plate as an RF read-out circuit component. Specifically, a 24 element imaging array is designed and validated to operate within 6 – 12 GHz band with subwavelength resonators to demonstrate the possibility of constructing low-cost high-resolution microwave surface imaging arrays by utilizing the microfluidics based reconfiguration techniques. The presented work emphasizes system level implementation of the proposed devices by integrating them with micropump units, controller boards, and investigating their reliability performances under higher power RF excitations.

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Rodriguez, Herrera Diego. "Antenna characterisation and optimal sampling constraints for breast microwave imaging systems with a novel wave speed propagation algorithm." IEEE, 2014. http://hdl.handle.net/1993/31907.

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Breast microwave imaging (BMI) is a novel modality that complements current breast screening tools. Microwave radar imaging creates a radar cross-section (reflection) map of the breast. The difference in permittivity between healthy and malignant tissue is between 10-50%. This contrast is significantly higher than that obtained with x-rays and supports the use of microwave imaging for breast cancer diagnosis. Prior to widespread clinical use, some areas require further study. Firstly, the performance of three different antennas was carried out, to assess their suitability for a BMI system. Secondly, the sampling constraint of a circular scan geometry was studied and tested using experimental phantoms and these antennas. For accurate breast BMI reconstruction, the transmission speed of the radio waves inside the breast must be determined. The tissue composition of each patient is different, making this task challenging. This work presents an algorithm for wave speed estimation in different mediums. February 2017

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Cracraft, Michael Andrew. "Mobile array designs with ANSERLIN antennas and efficient, wide-band PEEC models for interconnect and power distribution network analysis." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/mcthesis20070623_09007dcc80374999.pdf.

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Thesis (Ph. D.)--University of Missouri--Rolla, 2007. Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 16, 2007) Includes bibliographical references (p. 134-136).

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Tuo, Mingguang, Min Liang, Jitao Zhang, and Hao Xin. "Time-Domain THz Near-Field Imaging Incorporating Hadamard Multiplexing Method." IEEE, 2016. http://hdl.handle.net/10150/622785.

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Photoconductive antenna (PCA) array based THz near-field imager incorporating Hadamard multiplexing method is developed in this work. By using a 2 × 2 dipole antenna array as the THz transmitter, the system signal-to-noise ratio (SNR) is demonstrated to be improved by a factor of 2 as the theory predicts. Additionally, a 2-D scanning of a metallic structure on a THz-transparent substrate (with a total scanning area of 1 × 1 mm2) is experimentally implemented. Correlation coefficient estimation is made afterwards to quantify the reconstructed image quality.

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21

Ahmed, Sherif Sayed Aboelyazeed [Verfasser], Lorenz-Peter [Akademischer Betreuer] Schmidt, and Thomas [Akademischer Betreuer] Zwick. "Electronic Microwave Imaging with Planar Multistatic Arrays / Sherif Sayed Aboelyazeed Ahmed. Gutachter: Lorenz-Peter Schmidt ; Thomas Zwick." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2013. http://d-nb.info/1076166806/34.

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22

Ren, Yu-Jiun. "Microwave and millimeter-wave rectifying circuit arrays and ultra-wideband antennas for wireless power transmission and communications." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1294.

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23

Biswas, Indraneil. "Systems design of a millimeter wave interferometer using a concentric ring antenna array and image plane beam combination." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 110 p, 2008. http://proquest.umi.com/pqdweb?did=1650507961&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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24

Öjefors, Erik. "Integrated Antennas : Monolithic and Hybrid Approaches." Doctoral thesis, Uppsala University, Department of Engineering Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7142.

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This thesis considers integration of antennas and active electronics manufactured on the same substrate. The main topic is on-chip antennas for commercial silicon processes, but hybrid integration using printed circuit board technology is also addressed.The possible use of micromachining techniques as a means of reducing substrate losses of antennas manufactured on low resistivity silicon wafers is investigated. Compact dipole, loop, and inverted-F antennas for the 20-40 GHz frequency range are designed, implemented, and characterized. The results show significantly improved antenna efficiency when micromachining is used as a post-processing step for on-chip antennas manufactured in silicon technology.High resistivity wafers are used in a commercial silicon germanium technology to improve the efficiency of dipole antennas realized using the available circuit metal layers in the process. Monolithically integrated 24 GHz receivers with on-chip antennas are designed and evaluated with regard to antenna and system performance. No noticeable degradation of the receiver performance caused by cross talk between the antenna and the integrated circuit is observed.For low frequency antenna arrays, such as base station antennas, hybrid integration of active devices within the antenna aperture is treated. A compact varactor based phase shifter for traveling wave antenna applications is proposed and evaluated. Electrically steerable traveling wave patch antenna arrays, with the phase shifters implemented in the same conductor layer as the radiating elements, are designed and manufactured in microstrip technology. It is experimentally verified that the radiation from the feed network and phase shifters in the proposed antenna configuration is small.

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25

Adnan, S. "Ultra-wideband antenna design for microwave imaging applications. Design, optimisation and development of ultra-wideband antennas for microwave near-field sensing tools, and study the matching and radiation purity of these antennas within near field environment." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5750.

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Near field imaging using microwave in medical applications has gain much attention recently as various researches show its high ability and accuracy in illuminating object comparing to the well-known screening tools such as Magnetic Resonance Imaging (MRI), digital mammography, ultrasound etc. This has encourage and motivate scientists continue to exploit the potential of microwave imaging so that a better and more powerful sensing tools can be developed. This thesis documents the development of antenna design for microwave imaging application such as breast cancer detection. The application is similar to the concept of Ground Penetrating Radar (GPR) but operating at higher frequency band. In these systems a short pulse is transmitted from an antenna to the medium and the backscattered response is investigated for diagnose. In order to accommodate such a short pulse, a very wideband antenna with a minimal internal reflection is required. Printed monopole and planar metal plate antenna is implemented to achieve the necessary operating wide bandwidth. The development of new compact printed planar metal plate ultra wide bandwidth antenna is presented. A generalized parametric study is carried out using two well-known software packages to achieve optimum antenna performance. The Prototype antennas are tested and analysed experimentally, in which a reasonable agreement was achieved with the simulations. The antennas present an excellent relative wide bandwidth of 67% with acceptable range of power gain between 3.5 to 7 dBi. A new compact size air-dielectric microstrip patch-antenna designs proposed for breast cancer detection are presented. The antennas consist of a radiating patch mounted on two vertical plates, fed by coaxial cable. The antennas show a wide bandwidth that were verified by the simulations and also confirmed experimentally. The prototype antennas show excellent performance in terms the input impedance and radiation performance over the target range bandwidth from 4 GHz to 8 GHz. A mono-static model with a homogeneous dielectric box having similar properties to human tissue is used to study the interaction of the antenna with tissue. The numerical results in terms the matching required of new optimised antennas were promising. An experimental setup of sensor array for early-stage breast-cancer detection is developed. The arrangement of two elements separated by short distance that confined equivalent medium of breast tissues were modelled and implemented. The operation performances due to several orientations of the antennas locations were performed to determine the sensitivity limits with and without small size equivalent cancer cells model. In addition, a resistively loaded bow tie antenna, intended for applications in breast cancer detection, is adaptively modified through modelling and genetic optimisation is presented. The required wideband operating characteristic is achieved through manipulating the resistive loading of the antenna structure, the number of wires, and their angular separation within the equivalent wire assembly. The results show an acceptable impedance bandwidth of 100.75 %, with a VSWR < 2, over the interval from 3.3 GHz to 10.0 GHz. Feasibility studies were made on the antenna sensitivity for operation in a tissue equivalent dielectric medium. The simulated and measured results are all in close agreement.

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26

Adnan, Shahid. "Ultra-wideband antenna design for microwave imaging applications : design, optimisation and development of ultra-wideband antennas for microwave near-field sensing tools, and study the matching and radiation purity of these antennas within near field environment." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5750.

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Near field imaging using microwave in medical applications has gain much attention recently as various researches show its high ability and accuracy in illuminating object comparing to the well-known screening tools such as Magnetic Resonance Imaging (MRI), digital mammography, ultrasound etc. This has encourage and motivate scientists continue to exploit the potential of microwave imaging so that a better and more powerful sensing tools can be developed. This thesis documents the development of antenna design for microwave imaging application such as breast cancer detection. The application is similar to the concept of Ground Penetrating Radar (GPR) but operating at higher frequency band. In these systems a short pulse is transmitted from an antenna to the medium and the backscattered response is investigated for diagnose. In order to accommodate such a short pulse, a very wideband antenna with a minimal internal reflection is required. Printed monopole and planar metal plate antenna is implemented to achieve the necessary operating wide bandwidth. The development of new compact printed planar metal plate ultra wide bandwidth antenna is presented. A generalized parametric study is carried out using two well-known software packages to achieve optimum antenna performance. The Prototype antennas are tested and analysed experimentally, in which a reasonable agreement was achieved with the simulations. The antennas present an excellent relative wide bandwidth of 67% with acceptable range of power gain between 3.5 to 7 dBi. A new compact size air-dielectric microstrip patch-antenna designs proposed for breast cancer detection are presented. The antennas consist of a radiating patch mounted on two vertical plates, fed by coaxial cable. The antennas show a wide bandwidth that were verified by the simulations and also confirmed experimentally. The prototype antennas show excellent performance in terms the input impedance and radiation performance over the target range bandwidth from 4 GHz to 8 GHz. A mono-static model with a homogeneous dielectric box having similar properties to human tissue is used to study the interaction of the antenna with tissue. The numerical results in terms the matching required of new optimised antennas were promising. An experimental setup of sensor array for early-stage breast-cancer detection is developed. The arrangement of two elements separated by short distance that confined equivalent medium of breast tissues were modelled and implemented. The operation performances due to several orientations of the antennas locations were performed to determine the sensitivity limits with and without small size equivalent cancer cells model. In addition, a resistively loaded bow tie antenna, intended for applications in breast cancer detection, is adaptively modified through modelling and genetic optimisation is presented. The required wideband operating characteristic is achieved through manipulating the resistive loading of the antenna structure, the number of wires, and their angular separation within the equivalent wire assembly. The results show an acceptable impedance bandwidth of 100.75 %, with a VSWR < 2, over the interval from 3.3 GHz to 10.0 GHz. Feasibility studies were made on the antenna sensitivity for operation in a tissue equivalent dielectric medium. The simulated and measured results are all in close agreement.

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Rida, Amin Hassan. "Integrated RF modules and passives on low-cost flexible materials for applications up to the mm-wave frequency range." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39552.

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The objective of the proposed research is to develop solutions for High-Performance Low-Cost Passives for Radar, Identification, and Communication Applications up to mm-Wave Frequencies. This research will bring to the table potential solutions that will meet three main requirements: small size (or low weight), high performance, and low cost. This research embarks on antenna design and development for passive RFID tags on LCP substrates, and then a transition towards lower cost modules investigates and explores the possibilities of using paper as RF substrates with inkjet printing as a low cost fabrication technology. Modules such as dual band antenna for Wifi frequencies (2.4 GHz and 5 GHz) and UWB (up to 10GHz) on paper substrate using inkjet printing are presented. This work then bridges into developing higher frequency modules. These include: highly selective filter design on LCP for X-band Radar application to be used as a benchmark for an easy adjustment for higher frequencies, and antenna modules LCP using inkjet printing for communication such as mm-Wave WLAN or WPAN. A transition into mm-Wave Modules then takes place for the general realization of low-cost high-performance mm-Wave modules and more specifically the low cost automotive radar. After proposing an architecture for integrated mm-Wave module, this work then investigates 2D/3D interconnections (and their integration with antennas) on LCP using conventional etching design guidelines up to 100GHz. Antenna arrays that are implemented with phase shifters for beam steering are then designed using edge fed and multilayer technology. Furthermore, crosstalk reductions for highly dense transmission lines are analyzed via simulations for the optimum performance and space saving of such mm-Wave modules such as the IC interface where space restrictions are strictly enforced.

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28

Browne, Kenneth Edward. "High Resolution RADAR Imaging via a Portable Through-Wall MIMO System Employing a Low-Profile UWB Array." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306617106.

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29

El, Kanfoud Ibtissam. "Résolution de problèmes de rayonnement électromagnétique appliqués à l’imagerie médicale avec FreeFEM++." Thesis, Université Côte d'Azur (ComUE), 2019. http://www.theses.fr/2019AZUR4000/document.

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L'utilisation des microondes pour le diagnostic est en plein essor dans le domaine médical. Une des toutes dernières applications concerne la détection d'AVC (Accident vasculaire Cérébral) par imagerie microonde. La Société EMTensor GmbH basée à Vienne en Autriche étudie actuellement un tel système en collaboration avec le LEAT, le LJAD de l’Université Côte d’Azur et le LJLL de Sorbonne Université, pour le diagnostic et le contrôle de l'efficacité de traitement. Le but de ce travail était de modéliser le système de mesure de l'imagerie du cerveau, développé par la société EMTensor GmbH. Il s'agit d'un système d'émission/réception composé de 160 antennes disposées en 5 couronnes de 32 antennes réparties sur une cuve métallique cylindrique de section circulaire semi-ouverte. Un des enjeux majeurs de ce travail consiste en la modélisation et la simulation électromagnétique (EM) du système complet incluant un modèle réaliste de cerveau. La difficulté réside à la fois dans la taille du problème EM à simuler en raison du rapport entre la taille considérable du système et la taille très faible de certaines inhomogénéités à l’intérieur du cerveau, et dans la grande hétérogénéité des permittivités diélectriques présentes à l’intérieur du cerveau. Nous avons décidé d’utiliser un code open source, FreeFem++ pour cette modélisation car il permet de déployer du calcul hautement parallèle et la décomposition de domaines, qui sont bien adaptés à la complexité du problème EM. Dans un premier temps, nous avons comparé les résultats de simulation du système de mesure à vide (sans le cerveau) aux mesures et aux résultats obtenus par le logiciel de simulation EM HFSS basé sur la FEM comme FreeFem++. Nous avons ensuite simulé un modèle de tête tridimensionnel virtuel, à partir de coupe d’image du cerveau (scanner et IRM), en partenariat avec EMTensor en recherchant la position et le type d'AVC (ischémique et hémorragique). L'influence du bruit de mesure, la valeur du gel d'adaptation utilisé, le couplage entre les capteurs et le couplage entre la tête et les capteurs sont également étudiés. Afin de valider ces modèles, deux cas simples ont été étudiés. Un grand tube et un petit tube en plastique sont remplis de liquide d'adaptation symbolisant les caractéristiques diélectriques d'un cerveau afin de retrouver la forme du tube utilisé. Nous avons montré qu’il est possible de développer des algorithmes de reconstruction pour montrer permettant de retrouver la forme des objets par imagerie qualitative. Enfin, avec les partenaires et l'entreprise d'EMTensor nous avons appliqué une méthode quantitative à la détection d’un AVC ischémique par la tomographie microonde. Le problème direct repose sur l’utilisation de FreeFem++, en utilisant des éléments d'ordre supérieur et des préconditionneurs parallèles pour la méthode de décomposition de domaine. Nous avons résolu le problème inverse par un algorithme de minimisation, afin de reconstruire des images tomographiques du cerveau dans des temps compatibles avec les impératifs médicaux définis par les cliniciens The use of microwaves for diagnosis is booming in the medical field. One of the latest applications is the detection of strokes by microwave imaging. The company EMTensor GmbH based in Vienna, Austria is currently studying such a system in collaboration with LEAT, the LJAD of the Côte d’Azur University and the LJLL of Sarbonne University, for the diagnosis and control of the treatement efficiency. The purpose of this work is to model the brain imaging measurement system developed by EMTensor GmbH. It is a transmission/ reception system consisting of 160 antennas arranged in 5 rings of 32 antennas distributed on a cylinder metal tank of semi-open circular section. One of the major issues of this work is the modeling and electromagnetic simulation (EM) of the complete system including a realistic brain model. The difficulty lies both in the size of the EM problem to be simulated beacause of the relationship between the considerable size of the system and the the very small size of certain inhomogeneities within the brain, and the great heterogeneity of the dielectric permittivities present inside the brain. We decided to use an open source software, FreeFem++ for this modelling because it is well adapted to high performance computing through domain decomposition methods, which is mandatory for the complexity of the EM problem. First, we compared the simulation results of the vacuum matching measurement system (without the brain) to the measurements and the results obtained by the FEM-based EM HFSS simulation software to those obtained by FreeFem++. We then simulated a virtual threedimensional head model, from brain imaging system cuts (CT scan and MRI), in partnership with EMTensor, looking for the position and type of stroke (ischemic and hemorragic). The influence of the measurement noise, the value of the adaptation gel used, the coupling between the sensors and the coupling between the head and the sensors are also studied. In order to validate these models, two simple cases have been studied. A large tube and a small plastic tube are fielld with adaptation liquid with the dielectric characteristic of a brain to find the shape of the tubes used by qualitative imaging. Finally, with the MEDIMAX project partners and the EMTensor company we applied a quantitative method to the detection of ischemic stroke by the microwave tomography. The direct problem has been solved with the help of FreeFem++, using hight order elements and parallel preconditioners for the domain decomposition method. We solved the inverse problem by a minimization algorithm, in order to reconstruct tomographic images of the brain in times compatible with medical imperatives defined by clinicians.”

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Nounouh, Soufiane. "Protocoles de mesure et de calibrage de champs électromagnétiques en vue de l'imagerie par diffraction d'objets faiblement enfouis." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4750/document.

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Cette thèse est consacrée à la mise en place d'un système hyperfréquence dédié à l'imagerie du proche sous-sol. L'analyse de l'onde mesurée après interaction de l'onde incidente avec le milieu permet de remonter aux propriétés électromagnétiques de la structure illuminée. Ici, nous choisissons d'utiliser une seule fréquence en s'appuyant sur une configuration multistatique pour garantir une meilleure diversité de l'information.L'imagerie quantitative exige un calibrage minutieux des données mesurées après correction des erreurs expérimentales. Un calibrage a été donc proposé, basé sur la mesure du diagramme de rayonnement de chaque antenne. Celles-ci sont modélisées quantitativement en champ proche grâce à une combinaison de fils sources adéquatement optimisée. Ce calibrage, rapide et simple, ne nécessite pas d'objets de calibrage supplémentaires. Il a été d'abord testé dans le cas de la diffraction par des objets 2D en espace libre, puis dans le cas d'objets faiblement enfouis. Les champs calibrés servent de données d'entrée à des algorithmes d'inversion. En terme de localisation, les résultats obtenus sont très satisfaisants. Quant à la caractérisation, la configuration stratifiée apparaît bien moins propice que la configuration en espace libre, de part la faible quantité d'information disponible. Des changements ont été apportés à la configuration (différentes antennes avec ou sans orientation) dans l'optique d'améliorer le rapport signal à bruit. Bien que les reconstructions des permittivité soient encore perfectibles, les premiers résultats sont intéressants d'autant plus que les algorithmes n'exploitent aucune information a-priori sur la cible This thesis is devoted to the development of a microwave system dedicated to subsurface imaging applications. The analysis of the measured wave after the interaction with the medium allows to retrieve the electromagnetic properties of the probed structure. Here, we choose a single frequency operating mode combined with a multistatic configuration in order to improve the information diversity.Quantitative imaging requires a high-precision calibration of the measured data even after a careful correction of experimental errors. Thus, a calibration method is proposed, exploiting the measurement in free-space of the radiation pattern of each antenna. These patterns are quantitatively modeled thanks to an optimized linear combination of elementary sources positioned on the antenna's aperture. This simple and efficient calibration avoids additional measurements with calibration objects. This method provides successful results in a 2D free space scattering problem, as well as in the shallowly buried targets case.The calibrated data serve as inputs to inversion algorithms. As localization is concerned, very satisfactory detection results are obtained. Regarding the characterization aspects, the results indicate that the stratified configuration is less suitable than the free space configuration, due to its lack of spatial information. In order to improve the signal-to-noise ratio, some amendments are made to the experimental configuration (different antennas with or without orientation). Although the permittivity reconstructions are perfectible, the first results are promising especially since no a-priori on the targets has been inserted in the inversion algorithm so far

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31

Adnan, S., Raed A. Abd-Alhameed, Hmeda I. Hraga, Issa T. Elfergani, James M. Noras, and Rosemary A. Halliwell. "Microstrip Antenna for Microwave Imaging Application." 2011. http://hdl.handle.net/10454/5471.

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yes A compact microstrip antenna design to be used in breast cancer detection is presented. The antenna consists of a radiating patch mounted on two vertical plates, fed by coaxial cable. A study is carried out on different parameters of the antenna. Simulation results show that the antenna possesses a wide bandwidth and this is confirmed experimentally. In experiments, a homogeneous dielectric box, having similar properties to human tissue is used to study the interaction of the antenna with tissue. Even without added matching medium or lumped loads there is good matching when the antenna is in contact with the tissue. Finally a two-element antenna array is investigated numerically, with promising results. MSCRC

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32

Wood, Ian. "Linear tapered slot antenna for imaging arrays." Thesis, 2007. http://hdl.handle.net/1828/283.

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A prototype imaging array utilizing tapered slot antenna elements is investigated for potential use in radio astronomy. The design utilizes a previously reported substrate integrated waveguide style feed for the antenna element. The reported behavior of a tapered slot antenna is reproduced within CST Microwave Studio simulator, and the design parameters in the previous design were ported to a higher frequency and adjusted to increase directivity. Approximately symmetric 3 dB beamwidths are achieved in the simulator. Array simulation is limited in scope; a prototype, sixteen element planar array was fabricated and measured. Mutual coupling effects between elements cause adverse radiation performance compared to simulated predictions. Array performance is improved by using an alternate array configuration that introduced electrical boundaries between adjacent elements. Cross-polarization performance and array element spacing remain significant challenges to the antenna and feed technology for use in radio astronomy.

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LEE, HUA-JUN, and 李驊峻. "Broadband antenna Design for Microwave Imaging Applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/4v5keb.

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碩士 亞東技術學院 資訊與通訊工程研究所 105 The circular polarized antenna design is on demand for the global position system (GPS) which is one of the global communication applications. This paper investigates a broadband circular polarized antenna design for microwave imaging applications. Firstly, the novel design approach of the circular polarized dipole antenna is proposed to have features of very wide bandwidth and very stable gain by using a metal box instead of the method by changing the radiation pattern. However, the proposed method makes fabrication and construction more complicated. Subsequently, employing the proposed broadband circular polarized antenna design for microwave imaging is discussed in details. The operating principle of microwave imaging is a process through applying antenna to transmit the microwave signal upon the objective target, and then the signal is reflected by the target back to the receiving antenna for image data processing. The major factor affecting the imaging quality directly is the resolution which is related to the frequency of the antenna. The higher the frequency was, the better the resolution got. Nevertheless, for the reason of the signal-to-noise ratio affects the contrast, the signal-to-noise ratio will deteriorate by increasing the frequency. In this paper, the simulation software is developed to analyze the imaging processing of the objects, such as metal sphere and the blood vessel in the simulated human head. After that, the imaging of the objective target can be obtained by using the data from the receiving echo signals which are the reflected signal from the surface of the target.

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Adnan, S., Raed A. Abd-Alhameed, Hmeda I. Hraga, Issa T. Elfergani, and Mark B. Child. "Compact Microstrip Antenna Design for Microwave Imaging." 2010. http://hdl.handle.net/10454/4790.

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Yes An ultra-wideband microstrip antenna design is considered with respect to applications in breast cancer detection. The underlying design concept is based on ground penetrating radar (GPR). Simulated and measured prototype performance show excellent performance in the input impedance and radiation pattern over the target range from 4 GHz to 8 GHz. The 4 GHz to 8GHz frequency band for microwave imaging perform better in comparison with other microwave frequencies. The antenna also shows a reasonable uniform radiation performance in the broadside direction which contributes to the reduction of clutter levels, thus aiding the reconstruction quality of the final image.

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Markley, Loic. "Subwavelength Imaging using Scanning Near-field Antenna Arrays." Thesis, 2013. http://hdl.handle.net/1807/65518.

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This thesis examines a series of near-field antenna arrays used to perform subwavelength focusing and subwavelength imaging outside the extreme near field. For this purpose, slot and dipole arrays have been designed to produce a subwavelength focal spot at a distance of a quarter wavelength from the array. The dipole arrays are then used as scanning probes to produce images with subwavelength resolution based on perturbations in the scattered field. Unlike negative-refractive-index metamaterial superlenses, the imaging resolution is not affected by losses in the array. Furthermore, the arrays are simple to fabricate and are frequency scalable up to Terahertz frequencies and beyond. A near-field analogue to classic antenna-array theory called ``shifted beam theory'' is presented as a design tool. Based on the linear independence of element field patterns in the near field, this theory is very intuitive and provides a simplified way to calculate the element current weights necessary to generate a given target near-field pattern. Two-dimensional near-field subwavelength focusing is demonstrated using a slotted transmission-screen, or ``meta-screen'', under plane-wave incidence. At a distance of a quarter wavelength, the transverse electric field was measured in experiment to have a full-width half-maximum beamwidth of 0.40 by 0.27 wavelengths. This is compared to a single slot transmission-screen which had a beamwidth of 0.60 by 0.58 wavelengths. Broadside and end-fire dipole arrays are used to perform subwavelength imaging in one and two dimensions, respectively. The experimental minimum resolvable separation between two objects at a quarter-wavelength distance was 0.26 wavelengths using the end-fire array probe, as compared to 0.43 wavelengths for a single monopole probe. For an experiment using eight objects scattered over a one-square-wavelength area, however, the array probe imaging resolution remained around 0.25 wavelengths while the baseline monopole probe was no longer able to resolve any of the objects. Experiments were also conducted using objects buried behind a dielectric barrier as well as objects immersed within a dielectric. These results were consistent with the resolution improvements observed in the free-space resolution experiments.

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Guo, Yong. "Millimeter-wave integrated-circuit horn-antenna imaging arrays." Thesis, 1992. https://thesis.library.caltech.edu/2977/1/Guo_y_1992.pdf.

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A new millimeter-wave, integrated-circuit, back-to-back, horn-antennamixer array is presented. The configuration of the array is one called "displaced back-to-back horn-antenna array," which consists of a set of forward- and backward-looking horns made with a set of silicon wafers. The front side is used to receive the incoming signal, and the back side is used to feed the local oscillator. IF is led out from the side of the array. Pyramidal-shaped horns in silicon bounded by (111) crystal planes were formed by anisotropic etching of the silicon wafers. The power received by the horns is picked up by antenna probes suspended on thin silicon-oxynitride membranes inside the horns. The array is fully two-dimensional, and the horns are made simultaneously by integrated-circuit processing techniques. Aperture efficiency of the horn-antenna array has been improved up to 72 %, and system coupling efficiency is 36 %. In the efficiency measurements, a new thin-film, power-density meter is developed for measuring the asolute power densities. The main applications of the array include imaging, remote sensing and plasma diagnostics.

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37

Noroozian, Omid. "Superconducting Microwave Resonator Arrays for Submillimeter/Far-infrared Imaging." Thesis, 2012. https://thesis.library.caltech.edu/7161/6/PhDthesis_OmidNoroozian_2012_v9.pdf.

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Superconducting microwave resonators have the potential to revolutionize submillimeter and far-infrared astronomy, and with it our understanding of the universe. The field of low-temperature detector technology has reached a point where extremely sensitive devices like transition-edge sensors are now capable of detecting radiation limited by the background noise of the universe. However, the size of these detector arrays are limited to only a few thousand pixels. This is because of the cost and complexity of fabricating large-scale arrays of these detectors that can reach up to 10 lithographic levels on chip, and the complicated SQUID-based multiplexing circuitry and wiring for readout of each detector. In order to make substantial progress, next- generation ground-based telescopes such as CCAT or future space telescopes require focal planes with large-scale detector arrays of 104–106 pixels. Arrays using microwave kinetic inductance detectors (MKID) are a potential solution. These arrays can be easily made with a single layer of superconducting metal film deposited on a silicon substrate and pattered using conventional optical lithography. Furthermore, MKIDs are inherently multiplexable in the frequency domain, allowing ∼ 103 detectors to be read out using a single coaxial transmission line and cryogenic amplifier, drastically reducing cost and complexity. An MKID uses the change in the microwave surface impedance of a superconducting thin-film microresonator to detect photons. Absorption of photons in the superconductor breaks Cooper pairs into quasiparticles, changing the complex surface impedance, which results in a perturbation of resonator frequency and quality factor. For excitation and readout, the resonator is weakly coupled to a transmission line. The complex amplitude of a microwave probe signal tuned on-resonance and transmitted on the feedline past the resonator is perturbed as photons are absorbed in the superconductor. The perturbation can be detected using a cryogenic amplifier and subsequent homodyne mixing at room temperature. In an array of MKIDs, all the resonators are coupled to a shared feedline and are tuned to slightly different frequencies. They can be read out simultaneously using a comb of frequencies generated and measured using digital techniques. This thesis documents an effort to demonstrate the basic operation of ∼ 256 pixel arrays of lumped-element MKIDs made from superconducting TiNx on silicon. The resonators are designed and simulated for optimum operation. Various properties of the resonators and arrays are measured and compared to theoretical expectations. A particularly exciting observation is the extremely high quality factors (∼ 3 × 107) of our TiNx resonators which is essential for ultra-high sensitivity. The arrays are tightly packed both in space and in frequency which is desirable for larger full-size arrays. However, this can cause a serious problem in terms of microwave crosstalk between neighboring pixels. We show that by properly designing the resonator geometry, crosstalk can be eliminated; this is supported by our measurement results. We also tackle the problem of excess frequency noise in MKIDs. Intrinsic noise in the form of an excess resonance frequency jitter exists in planar superconducting resonators that are made on dielectric substrates. We conclusively show that this noise is due to fluctuations of the resonator capacitance. In turn, the capacitance fluctuations are thought to be driven by two-level system (TLS) fluctuators in a thin layer on the surface of the device. With a modified resonator design we demonstrate with measurements that this noise can be substantially reduced. An optimized version of this resonator was designed for the multiwavelength submillimeter kinetic inductance camera (MUSIC) instrument for the Caltech Submillimeter Observatory.

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38

Adnan, S., Ahmed F. Mirza, Raed A. Abd-Alhameed, et al. "Microwave antennas for near field imaging." 2015. http://hdl.handle.net/10454/9108.

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No Near field imaging using microwaves in medical applications has gained much attention recently as various researchers have shown its capability and accuracy in identifying features of interest compared to well-known screening tools. This paper documents microwave imaging experiments for breast cancer detection. A simple phantom consisting of a plastic container with a low dielectric material imitating fatty tissue and a high dielectric constant object emulating tumor is scanned with a UWB microstrip antenna between 4 to 8 GHz. The measured results indicate that the prototype is a good candidate for imaging application.

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Abdalla, Mohamed. "Metamaterial-Inspired CMOS Tunable Microwave Integrated Circuits For Steerable Antenna Arrays." Thesis, 2009. http://hdl.handle.net/1807/17720.

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This thesis presents the design of radio-frequency (RF) tunable active inductors (TAIs) with independent inductance (L) and quality factor (Q) tuning capability, and their application in the design of RF tunable phase shifters and directional couplers for wireless transceivers. The independent L and Q tuning is achieved using a modided gyrator-C architecture with an additional feedback element. A general framework is developed for this Q- enhancement technique making it applicable to any gyrator-C based TAI. The design of a 1.5V, grounded, 0.13um CMOS TAI is presented. The proposed circuit achieves a 0.8nH-11.7nH tuning range at 2GHz, with a peak-Q in excess of 100. Furthermore, printed and integrated versions of tunable positive/negative refractive index (PRI /NRI) phase shifters, are presented in this thesis. The printed phase shifters are comprised of a microstrip transmission-line (TL) loaded with varactors and TAIs, which, when tuned together, extends the phase tuning range and produces a low return loss. In contrast, the integrated phase shifters utilize lumped L-C sections in place of the TLs, which allows for a single MMIC implementation. Detailed experimental results are presented in the thesis. As an example, the printed design achieves a phase of -40 to +34 degrees at 2.5GHz. As another application for the TAI, a reconfigurable CMOS directional coupler is presented in this thesis. The proposed coupler allows electronic control over the coupling coefficient, and the operating frequency while insuring a low return loss and high isolation. Moreover, it allows switching between forward and backward operation. These features, combined together, would allow using the coupler as a duplexer to connect a transmitter and a receiver to a single antenna. Finally, a planar electronically steerable patch array is presented. The 4-element array uses the tunable PRI/NRI phase shifters to center its radiation about the broadside direction. This also minimizes the main beam squinting across the operating bandwidth. The feed network of the array uses impedance transformers, which allow identical interstage phase shifters. The proposed antenna array is capable of continuously steering its main beam from -27 to +22 degrees of the broadside direction with a gain of 8.4dBi at 2.4GHz.

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Hsueh, Hsiang-Chun, and 薛向均. "Design of Worldwide Interoperability for Microwave Access High Gain Antenna Arrays." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/88234125513697526811.

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碩士 國立交通大學 電信工程系所 95 WiMAX (Worldwide Interoperability for Microwave Access) has the advantages: wireless, far-distance transmission and wideband. It will be one of the wireless communication system standards in the next generation. In this thesis, we study high gain antenna arrays suitable for 3.3GHz-3.8GHz WiMAX communication system, and it also satisfies ETSI specification. We use wideband microstrip antennas, increase the height of antenna structure and design of the feeding network to let the antenna arrays can conform to this system bandwidth and gain requirement.

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Pan, Ya-Ting, and 潘亞婷. "High-Gain Antenna Design for Microwave Imaging Detection of Abnormal Tissue." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/db4snq.

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碩士 正修科技大學 電子工程研究所 102 This thesis proposes the high-gain antenna design for microwave detection of non-normal tissue. The first is an ultra-wideband planar dipole antenna with symmetrical structure. This design has a directional radiation to achieve 6 dBi antenna gain. Instead of the complicated feeding network, only simple parameter adjustments are needed to achieve ultra-wide operation bandwidth of 3.1 ~ 10.6 GHz. The second design is a planar dipole antenna with band-notched function for ultra-wideband operation. We add one pair of interference elements on the first antenna structure. That element is not only introduces a mismatch between the input port and the antenna, but also cancel the radiating field over 5 ~ 6 GHz. A multiple-input multi-output antenna with ultra-wideband operation to detect abnormal tissue is also proposed. By using the design, the early-stage scan and alignment of abnormal tissue can be obtained.

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陳建宏. "Worldwide Interoperability for Microwave Access (WiMAX) High Gain Antenna Arrays with Electromagnetic Band-Gap Structure’s Applications." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/33644897125785238922.

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碩士 國立交通大學 電信工程系所 96 WiMAX (Worldwide Interoperability for Microwave Access) has the advantages: wireless, far-distance transmission and wideband. It will be one of the wireless communication system standards in the next generation. In this thesis, we will research high gain antenna arrays suitable for 3.4GHz-3.7GHz WiMAX communication system, and it also satisfies ETSI specification. We use microstrip antennas by increasing the height of antenna structure to let the antenna arrays can conform to this system bandwidth and gain requirement. In this thesis, we will design an electromagnetic band-gap(EBG) structure without via. We also label it to photonic band-gap(PBG). By combining it with microstrip antenna, we can understand its effects on the properties of antenna. Further more, we can improve the radiation patter of the microstrip antenna and suppress surface wave’s exitation in the substrate.

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Mirza, Ahmed F., Chan H. See, Isah Danjuma, et al. "An Active Microwave Sensor for Near Field Imaging." 2017. http://hdl.handle.net/10454/11624.

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yes Near field imaging using microwaves in medical applications is of great current interest for its capability and accuracy in identifying features of interest, in comparison with other known screening tools. This paper documents microwave imaging experiments on breast cancer detection, using active antenna tuning to obtain matching over a wide bandwidth. A simple phantom consisting of a plastic container with a low dielectric material emulating fatty tissue and a high dielectric constant object emulating a tumor is scanned between 4 to 8 GHz with a UWB microstrip antenna. Measurements indicate that this prototype microwave sensor is a good candidate for such imaging applications. Yorkshire Innovation Fund, Research Development Project (RDP)

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Mohamed, Abdelhalim Mohamed Mamdouh. "Performance enhancement of ultra wideband antennas for communication and microwave imaging applications." 2012. http://hdl.handle.net/1993/5078.

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This thesis investigates omnidirectional and directional ultra wideband (UWB) antennas for communication and microwave imaging applications. To reduce interference with existing technologies, monopole antennas with efficient band-stop functions are introduced. Single and double slots acting as series resonators are used. Reduction in the antenna gain in the stop-band regions of about 19.5 dB is achieved. Central metal removal and ground plane size effects on the antenna performance are investigated. To eliminate signal distortion caused by such monopole antennas, phase centre behaviour over the entire frequency band of operation is investigated at different principle planes, which have not been done before. This study will also show how these antennas act in different communication scenarios and where the radiation will be coming from at different frequencies. The effect of including different slots with different shapes on the performance of phase centre of these antennas is also investigated. Different methods to minimize the antenna phase centre movement are studied. Novel microstrip antennas with UWB impedance and radiation pattern bandwidth and low cross polarization components are introduced to work over the frequency band from 3 to 20 GHz. The antennas introduced are double-layer structures in which the radiator is sandwiched between two identical partial ground planes or a partial ground plane is sandwiched between two radiators. Results show a significant reduction in the cross polarization components at all frequencies. A novel high gain UWB Vee dipole antenna with a UWB coaxial balun feed is introduced to cover the existing and future UWB communication applications. Different type of loadings such as a reflecting ground below the antenna, a dielectric sleeve over the UWB balun and conical dielectrics between the Vee plates are also used and studied that show enhanced gains and lower sidelobes. A miniaturized-type UWB Vee dipole antenna is also investigated for microwave imaging applications. The antenna has a small radiation aperture which makes it a good candidate for array type applications. Full wave analysis of studied antennas are done using Ansoft HFSS, finite-element-methods based software. Experimental investigations are done to confirm the accuracy of simulated results.

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Abdulhasan, R. A., R. Alias, K. N. Ramli, F. C. Seman, and Raed A. Abd-Alhameed. "High gain CPW‐fed UWB planar monopole antenna‐based compact uniplanar frequency selective surface for microwave imaging." 2019. http://hdl.handle.net/10454/16994.

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Yes In this article, a novel uniplanar ultra‐wideband (UWB) stop frequency selective surface (FSS) was miniaturized to maximize the gain of a compact UWB monopole antenna for microwave imaging applications. The single‐plane FSS unit cell size was only 0.095λ × 0.095λ for a lower‐operating frequency had been introduced, which was miniaturized by combining a square‐loop with a cross‐dipole on FR4 substrate. The proposed hexagonal antenna was printed on FR4 substrate with coplanar waveguide feed, which was further backed at 21.6 mm by 3 × 3 FSS array. The unit cell was modeled with an equivalent circuit, while the measured characteristics of fabricated FSS array and the antenna prototypes were validated with the simulation outcomes. The FSS displayed transmission magnitude below −10 dB and linear reflection phase over the bandwidth of 2.6 to 11.1 GHz. The proposed antenna prototype achieved excellent gain improvement about 3.5 dBi, unidirectional radiation, and bandwidth of 3.8 to 10.6 GHz. Exceptional agreements were observed between the simulation and the measured outcomes. Hence, a new UWB baggage scanner system was developed to assess the short distance imaging of simulated small metallic objects in handbag model. The system based on the proposed antenna displayed a higher resolution image than the antenna without FSS. The full-text of this article will be released for public view at the end of the publisher embargo on 29 Mar 2020.

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Ostadrahimi, Majid. "Near-field microwave tomography systems and the use of a scatterer probe technique." 2012. http://hdl.handle.net/1993/5035.

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This dissertation presents the contributions and the research conducted in developing and implementing Microwave Tomography (MWT) systems. MWT is an imaging modality which aims to interrogate an object of interest by microwave energy, and quantitatively “find” the interior spatial distribution of its dielectric properties using field measurements taken outside the object. Due to the inherent non-linearity of the MWT problem, a substantial amount of electromagnetic scattering data is required to ensure a robust inversion and quantitatively accurate imaging results. This research benefits a variety of applications including biomedical imaging, industrial non-destructive testing, and security applications. Developing a MWT system, requires many critical components including the bandwidth and polarization purity of the collected fields as well as calibration of the fields scattered by the object of interest. Two generations of MWT systems were designed, implemented, calibrated and tested at the University of Manitoba (UM). These systems aim different approaches for near-field measurements which are referred to as the direct and indirect methods. With regard to the antenna design, a novel methodology applicable to broadband planar antennas is introduced. This technique is based on a combination of field modelling, herein, the finite element method and transmission line modelling. In the first generation of the UM MWT systems, a suitable antenna system was utilized. The system under study was a prototype, where twenty-four co-resident antennas encircle the object of interest to directly measure the fields. In the second generation of the UM MWT systems, the feasibility of using a novel technique to indirectly measure the fields by a secondary array of near-field scatterer probes was studied. The technique is based on the Modulated Scatterer Technique (MST). In this system, antennas are called ``collectors", since the role of antennas are changed to collecting probes' scattered fields. A number of PIN diodes were utilized to activate the probes. Finally, the capability of the probe system was investigated and its performance with the previously constructed tomography systems was compared. Various dielectric phantoms were utilized to test the accuracy of the systems.

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Szazynski, Mitchel H. "Wireless power transfer: a reconfigurable phased array with novel feeding architecture." Thesis, 2018. https://doi.org/10.7912/C24H2M.

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Indiana University-Purdue University Indianapolis (IUPUI) This thesis proposes a reconfigurable phased array of antennas for wireless power transfer. The array finds use in many applications, from drone destruction (for defense) to wireless charging of robots and mobile devices. It utilizes a novel feeding architecture to greatly reduce the number of high cost elements (such as amplifiers and phase shifters) as well as the quantity of unused resources in the system. Upon the instruction of the CPU, the array can separate into any number of subarrays, each of which transmits power to a single receiver, steering its beam as the receiver changes location. Currently dormant elements in the array can be used to provide position information about the receivers, either via Radar, or by listening for beacons pulses from the receiver. All of this is made possible, with only 4 amplifiers and 3 phase shifters, by the proposed 4-Bus Method. The source signal is divided into four buses, which are respectively phase shifted by 270 degrees, 180 degrees, 90 degrees, and 0 degrees (no shifter required) and then amplified. The CPU calculates, based on the number and positions of the receivers / targets, what the amplitude and phase excitation must be at each element. Any phase and amplitude which could be required can be achieved by simply adding together appropriate quantities of the correct two buses. In order to achieve this, the key piece is the variable power divider. These differ from Wilkinson dividers in that the dividing ratio can be changed via an applied DC voltage. Therefore, at each junction, by properly diverting the power levels on each phase bus to their proper location, complete delocalization of both amplifiers and phase shifters can be achieved. A method has also been developed which helps overcome the limitations of each variable power divider. That is, in certain instances, it may be desirable to pass all the power to a single output port or the other, which is not a possibility inherently possible with the device. With the use of a unique combination of RF switches, the nodes achieve much enhanced flexibility. Finally, an intensive study is carried out, in an attempt to yield greater understanding, as well as quick, useful approximations, of the behaviors of both rectangular and hexagonal arrays of various sizes and beam steering angles for wireless power.

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Lata, Poonam. "Design, Development, And Integration Of A Meso-scale Eletrostatic Phase Shifter On Microwave Laminate." Thesis, 2011. http://hdl.handle.net/2005/2356.

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Recent developments in the area of microfabrication technologies, has enabled the fabrication of many radio frequency/microwave components with better performance and lower cost than possible with semiconductor based fabrication technology. Many of these microfabricated RF components such as switches and phase shifters, popularly known as RF MEMS, are aimed at reducing the insertion loss and improving other performance parameters such as linearity. For these devices size miniaturization is not necessarily important, as in practical subsystems, these components are integrated with RF front-ends on a laminate. This thesis deals with concepts of a low cost passive phase shifter fabricated in-situ on a microwave laminate. The operation of this Mesoscale Electrostatically actuated Phase shifter on microwave Laminate (MEPL) is similar to that of a micromachined distributed MEMS transmission line (DMTL) phase shifter. In spite of advantages of low losses, wide bandwidth, low DC power consumption and high linearity over semiconductor/MMIC technology, microfabricated phase shifters are often not used in field because of issues related to fabrication reliability, packaging and integration. On the other hand, the proposed MEPL will have all the advantages of conventional MEMS phase shifters with additional benefit of lower cost. Furthermore, these are integrable to form a monolithic phased array. A MEPL phase shifter of 50-bridges periodically distributed on the co-planar waveguide (CPW) transmission line is demonstrated in this thesis. MEMS air bridges are electrostatically actuated to vary the capacitance of the transmission line, which changes the phase velocity of the propagation RF signal, consequently phase at the output port. The realized MEPL is characterized for electromagnetic as well as electromechanical performance. The electromechanical characterization of this device is performed using a Laser Doppler Vibrometer (LDV). The measured data showed good agreement with the analytical data.. Major application of a phase shifter is in a phased array antenna system. MEPL is particularly suited for a monolithic phase array antenna. The proposed monolithic phased array antenna system fabrication approach utilizes extremely simple and economical modern printed circuit board technology to pattern the conventional microwave laminate and copper foil. A complete monolithic phased array antenna system is fabricated on a microwave laminate using an embedded phase shifter operating with electrostatic principles. Other components such as DC block and bias tee are integrated into the CPW-microstrip transitions to optimize the space and performance. Integrated phased array antenna is fabricated and tested to demonstrate the beam steering capability. Measured S11 is better than -15dB at the operating frequency of 9.8GHz. The beam steering capability is shown as proof of concept by showing the beam scan angle of 10deg with bias voltage of 125V. The mesoscale phase shifter demonstrated in this thesis has several advantages compared to micromachined phase shifters. The proposed fabrication approach does not use metal deposition/patterning process, which removes the need of high cost clean room and sophisticated films deposition equipments. Secondly, as there are no thin films used, stiction is not expected on phase shifters fabricated with this approach. Since this approach uses thicker metal films, the power handling capability is expected to be significantly higher than micromachined phase shifters. Since conventional phased array antenna system components are fabricated on a microwave laminate, micro machined phase shifters realized on semiconductor substrates are required to be packaged separately before integrating with such phased array circuits. Packaging of the micro-machined RF-MEMS/MEMS devices is still a major issue and contributes to a substantial part of the total cost. Unlike micromachined phase shifters which are required to be packaged and then embedded in phased array applications, device presented in this thesis is packaged in-situ. Compared to similar monolithic phased array antenna reported on silicon substrate which are limited by wafer size, these arrays can be easily extended for larger arrays on microwave laminate as these are available in large size. To summarize, the proposed fabrication approach for phase shifters overcomes many limitations of micromachined components for microwave applications while retaining most of their advantages compared to other existing approaches based on ferrites or semiconductor technologies.

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Dissertations / Theses on the topic 'Microwave imaging. Antenna arrays'

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