Дисертації з теми "Phase arrays"
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1
Colley, Alan David. "Phase-locking of CO2 waveguide laser arrays." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/848.
2
Soo, C. B. "Phase locked loop analysts for steerable antenna arrays." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487377.
Анотація:
The purpose of this work was to produce novel Phase Locked Loops (PLL) architectures for antenna array applications. The operational characteristics of these PLLs architectures are presented and are analysed theoretically. The first type ofPLL ar.c. hitecture presented is called the Phase Conjugating Locked Loops (PCLL). Three different topologies for this type are designed to provide the phase conjugation operation necessary for retrodirective antenna array action. PCLL .Type 1 operates under the circumstance that input radio frequency roRF is different . from the VCO output frequency rovco while Type 2 and 3 operate when both ofthese frequencies are equal to each other. I I The second type of PLL architecture, which is called the Variable Phase Locked Loop (VPLL), is designed to operate in transmit only operation as a spatial phase shifter. The beamforming operation of a VPLL based antenna array is obtained by baseband tuning ofthe VCO voltage. The last type of PLL architecture studied, the Phase Buffering Locked Loop (PBLL), is suitable for self-tracking receive only operation. The embodiment of this PLL is architecturally similar to that of PCLL Type 1 with the exception that a down' converter mixer is included after the VCO and an inverter is inserted before the VCO. For each of the PLL architectures comprehensive derivations of the output phase noise jitter noise equations including the effects of the non-linearity and non-idealistic mixer characteristics is presented. These RMS phase noise jitter equations are utilised in order to evaluate the steady state error of each PLL topology. Following the investigation of noise performance, the stability of PLL architectures is examined. Bode Plot and Polar Plot have been deployed to facilitate the investigation. The final investigation concentrates on the impact of multiple signals on PBLL self-tracking receiver antenna array.
3
Buckley, David. "Phase-locked, multiple ridge waveguide, semiconductor laser arrays." Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334692.
4
Merlano, Duncan Juan Carlos. "Phase synchronization scheme for very long baseline coherent arrays." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/96673.
Анотація:
Precise phase synchronization of clock or local oscillator signals over distributed systems is a recurring requirement in the design of a wide range of systems, with applications in telecommunications and, for example, in phased arrays. Addressing this requirement is a challenging task when the distance between the subsystems is large in terms of the wavelength and, in particular, when this electrical distance is time-varying.
Carrier phase synchronization is the most important challenge in order to implement distributed beamforming systems and to optimize their power efficiency. At the same time, phase synchronization is crucial for the implementation of distributed (bistatic / multistatic) radar systems.
In the last decades different techniques for remote phase synchronization have been proposed. In 1968 Thompson discussed, compared and classified the available techniques for reducing propagation induced phase fluctuations in frequency distribution systems and presented the principle of round trip stabilization systems. These phase synchronization schemes are Phase Locked Loops (PLL) in which the phase offset is measured directly for the signal which travels along the two-way path, and a direct feedback action closes the loop.
The most important challenge for the design of these systems is the implementation of a method for the discrimination between the waves that travel in opposite directions in the transmission channel. One approach that has been proposed in previous works to fulfill this requirement is the use of different frequencies.
This Ph.D. thesis dissertation presents a new scheme for remote carrier phase synchronization in which a set of tones with similar frequencies are simultaneously used to synchronize two separated stations. In the proposed scheme, the bandwidth required by the set of tones traveling along the loop can be reduced wherewith the phase fluctuations generated by the dispersive effects of the medium can be drastically reduced.
The proposed scheme was prototyped and tested in the laboratory, with satisfactory results, and a possible application of the phase synchronization prototype has been evaluated.
In order to show the excellent behavior of the phase synchronization prototype a simple distance measurement experiment has been carried out. In that experiment the variations of a distance are obtained from the variations of a measured phase using the synchronization prototype.
5
Harris, Edward Belden. "A study of phase-locking in Josephson junction arrays /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu148795015360062.
6
Kao, Tsung-Yu. "Surface-emitting distributed feedback terahertz quantum-cascade phase-locked laser arrays." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54235.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 111-114).
A new approach to achieve high-power, symmetric beam-pattern, single-mode THz emission from metal-metal waveguide quantum-cascade laser is proposed and implemented. Several surface-emitting distributed feedback terahertz lasers are coupled through the connection phase sectors between them. Through carefully choosing the length of phase sectors, each laser will be in-phase locked with each other and thus create a tighter beam-pattern along the phased-array direction. A clear proof of phase-locking phenomenon has been observed and the array can be operated in either in-phase or out-of-phase mode at different phase sector length. The phase sector can also be individually biased to provide another frequency tuning mechanism through gain-induced optical index change. A frequency tuning range of 1:5 GHz out of 3:9 THz was measured. Moreover, an electronically controlled "beam steering" device is also proposed based on the result of this work. This thesis focuses on the design, fabrication and measurement of the surface-emitting distributed feedback terahertz quantum-cascade phase-locked laser arrays.
by Tsung-Yu Kao.
S.M.
7
Herold, F. W., and J. A. Kaiser. "ELIMINATION OF SIDELOBE RESPONSE." International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/607377.
Анотація:
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, CaliforniaConventional phased arrays nominally sum the signals received by the elements prior to detection. By multiplying rather than summing signals received from pairs of elements, i.e., interferometer pairs, a set of Spatial Frequencies (SFs) is obtained. Obtaining the SFs requires employment of a multiple local oscillator technique. When summed, these spatial frequencies produce a single lobed (voltage) radiation pattern which, when passed through a biased detector, removes all sidelobes from the response at a small loss of desired signal power.
8
Chesworth, Andrew Alexander. "Mode control in thin slab, diode pumped solid state lasers." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/649.
9
Chu, Min. "Phase-shifting techniques for wireless multiple-antenna transmitter applications /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/6002.
10
Zarei, Hossein. "RF variable phase shifters for multiple smart antenna transceivers /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5964.
11
Alkhafaji, Nasr Nomas Hussein. "UHF and Microwave Phase-Modulated Scattering Array." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4998.
Анотація:
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.
12
Brown, Roger Keith. "Triangular proximity-coupled arrays : phase transition in a magnetic field and dynamical properties /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726282507655.
13
Loebel and Martin Bo Hjort. "Improvement of the Coherence Characteristics of Laser Diode Arrays Using Photorefractive Phase Conjugation." Thesis, Risoe National Laboratory, 1998. http://www.risoe.dk/rispubl/ofd/riso-r-1038.htm.
14
Marais, Sarel Jacobus. "The quadrifilar helix antenna and its application to wide angle phase-steered arrays." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/21675.
Анотація:
Thesis (MScIng)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: The quadrifilar helix antenna has frequently been employed to provide the wide angle, circularly polarized radiation pattern which is preferable for mobile satellite communications. A detailed study of this antenna and its varieties is presented. When used as an element in wide angle scanning arrays for aeronautical satellite tracking applications, the additional requirement of a low profile with light weight applies. This further complicates the realization of good circular polarization close to the horizon. A top disk is incorporated into various antenna structures in an effort to improve the radiation performance when used within a closely spaced array while reducing the height of the radiating element. The array performance of these elements are investigated which hints at a supported traveling mode aiding the ability to accomplish the wide angle beam steering. Subsequent study of leakywave antennas initiated the study and implementation of leaky-wave structures in phased arrays of quadrifilar helix elements.
AFRIKAANSE OPSOMMING: Die vierledige heliksantenna word dikwels gebruik vir toepassings wat ’n wye, sirkulêr gepolariseerde stralingspatroon benodig. ’n Verskeidenheid van hierdie antennas is noukeurig bestudeer en hul toepaslikheid vir mobiele sattelietkommunikasie ondersoek. Wanneer hierdie antennas in fase gestuurde skikkings gebruik word, word dit ook vereis dat die eenhede liggewig is met ’n lae profiel. Dit bemoeilik die verkryging van goeie sirkulêre polarisasie naby die horison aansienlik. In ’n poging om die wyehoek straling met kort antennas te verbeter, is ’n oorhoofse skyf tot verskillende heliksstrukture toegevoeg. In nou gespasieerde skikkings maak hierdie skywe ’n positiewe bydrae to wyehoekstralingeienskappe. Die invloed van lekmodusse wat binne die struktuur voortplant is ondersoek en gebruik in skikkings waarvan die bundel naby aan die horison gestuur word.
15
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.
16
Johannes, Michael T. "A fixed-point phase lock loop in a software defined radio." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FJohannes.pdf.
17
Oh, Jaesung. "Fabrication of Silver Nanoparticles by Solution Phase Method and Physical Characterization of Their Arrays." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1189564248.
18
Morgan, Frances Deirdre. "Optical study of noble metal nanostructured arrays : phase mapping of localized surface plasmon resonances." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709554.
19
Temir, Kaan. "True-time Delay Structures For Microwave Beamforming Networks In S-band Phased Arrays." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615386/index.pdf.
Анотація:
True time delay networks are one of the most critical structures of wideband phased-array antenna systems which are frequently used in self-protection and electronic warfare applications. In order to direct the main beam of a wideband phased-array antenna to the desired directionphase values, which are linearly dependent to frequency, are essential. Due to the phase characteristics of the true-time delay networks, beam squint problems for broadband phased array systems are minimized. In this thesis, different types of true-time delay structures are investigated for wideband phased array applications and a tunable S-band true-time delay network having delay over 1ns with high resolution is developed, designed, fabricated and measured. Lower-cost, smaller occupied area, digital/analog control mechanism and ease of implementation are the other features of the developed network. High delay values with high resolutions for wideband operation are achieved through the combination of several techniques
therefore the desired S-band TTD network is constructed with the synthesis of switched-transmission lines, constant-R networks and periodically-loaded transmission lines. Higher delay states are realized by the switched-transmission lines technique, while the method of constant R-network is used for the intermediate delay states. To increase the tuning flexibility, smaller delay states are accomplished by analog-voltage controlled periodically loaded transmission lines. A step-by-step procedure is followed during the design process of the S-band true time delay network. Firstly, each method used in the TTD network is analyzed in detail and developed for PCB implementation and the use of COTS components. Then, the designed structures are verified via linear and EM simulations performed by ADS2011®
. After that, the effects of production tolerances are examined to optimize each design for S-band operations. Moreover, the designed structures are fabricated by using PCB technology and measured. Finally, a software code is developed in MATLAB to generate the overall cascaded network with the help of measured data.
20
Roth, Matthias, Jörg Heber, and Klaus Janschek. "Concept for the fast modulation of light in amplitude and phase using analog tilt-mirror arrays." SPIE, 2017. https://tud.qucosa.de/id/qucosa%3A35124.
Анотація:
The full complex, spatial modulation of light at high frame rates is essential for a variety of applications. In particular, emerging techniques applied to scattering media, such as Digital Optical Phase Conjugation and Wavefront Shaping, request challenging performance parameters. They refer to imaging tasks inside biological media, whose characteristics concerning the transmission and reflection of scattered light may change over time within milliseconds. Thus, these methods call for frame rates in the kilohertz range. Existing solutions typically offer frame rate capabilities below 100 Hz, since they rely on liquid crystal spatial light modulators (SLMs). We propose a diffractive MEMS optical system for this application range. It relies on an analog, tilt-type micro mirror array (MMA) based on an established SLM technology, where the standard application is grayscale amplitude control. The new MMA system design allows the phase manipulation at high-speed as well.
The article studies properties of the appropriate optical setup by simulating the propagation of the light. Relevant test patterns and sensitivity parameters of the system will be analyzed. Our results illustrate the main opportunities of the concept with particular focus on the tilt mirror technology. They indicate a promising path to realize the complex light modulation at frame rates above 1 kHz and resolutions well beyond 10,000 complex pixels.
21
Topalli, Kagan. "A Monolithic Phased Array Using Rf Mems Technology." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608436/index.pdf.
Анотація:
This thesis presents a novel monolithic phased array implemented using the RF MEMS technology. The structure, which is designed at 15 GHz, consists of four linearly placed microstrip patch antennas, 3-bit distributed RF MEMS low-loss phase shifters, and a corporate feed network. The RF MEMS phase shifter employed in the system consists of three sections with a total of 28 unit cells, and it occupies an area of 22.4 mm 
2.1 mm. The performance of the phase shifters is improved using high-Q metal-air-metal capacitors in addition to MEMS switches as loading elements on a high-impedance coplanar waveguide transmission line. The phased array is fabricated monolithically using an in-house surface micromachining process, where a 1.2-&
#61549
m thick gold structural layer is placed on a 500-µ
m thick glass substrate with a capacitive gap of 2 &
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m. The fabrication process is simple, requires only 6 masks, and allows the implementation of various RF MEMS components on the same substrate, such as RF MEMS switches and phase shifters. The fabricated monolithic phased array occupies an area of only 6 cm &
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5 cm. The measurement results show that the phase shifter can provide nearly 20&
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/50&
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/95&
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phase shifts and their eight combinations at the expense of 1.5 dB average insertion loss at 15 GHz. The phase shifters can be actuated with 16 V, while dissipating negligible power due to its capacitive operation. It is also shown by measurements that the main beam can be steered to 4&
#61616
and 14&
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by suitable settings of the RF MEMS phase shifters.
22
Yoo, Sehoon. "Oriented arrays of single crystal TiO2 nanofibers by gas-phase etching: processing and characterization." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1117566246.
Анотація:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xix, 217 p.; also includes graphics (some col.) Includes bibliographical references (p. 199-217). Available online via OhioLINK's ETD Center
23
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.
Анотація:
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.
24
Kraczek, Jeffrey Read. "Piston Phase Measurements to Accelerate Image Reconstruction in Multi-Aperture Systems." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1323284036.
25
Rahman, Muhammad Mahboob Ur. "Distributed Beamforming and Nullforming: Frequency Synchronization Techniques, Phase Control Algorithms, and Proof-Of-Concept." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4904.
Анотація:
We describe a set of fundamental contributions to the design, analysis and implementation of distributed MIMO techniques in wireless networks. The main idea behind distributed MIMO is to organize groups of wireless transmitters and receivers into distributed antenna arrays to cooperatively achieve beamforming and spatial multiplexing gains in ad-hoc wireless networks. This technique promises orders-of-magnitude increases in wireless data rates, however it presupposes very stringent timing, carrier frequency and phase synchronization of the RF signals between the cooperating nodes in the array.
Specifically in this dissertation, we consider a sub-class of distributed MIMO systems called distributed MISO systems. In other words, we focus on distributed transmit arrays, wherein a group of N transmitters organize themselves into a virtual antenna array (VAA) to talk to a single-antenna receiver. While distributed MIMO involves virtual arrays on both transmit and receive ends, transmit arrays require real-time coordination, and therefore present unique challenges as compared to receive arrays.
We explore two specific MISO techniques: i) distributed beamforming and ii) distributed nullforming in this work. Beamforming involves focusing transmitted energy selectively in the direction of an intended receiver, and nullforming involves forming a "null" i.e. having the transmissions of the different array nodes cancel each other completely at a desired location. Beamforming has the potential of substantially increasing the energy efficiency of wireless communications, while nullforming allows multiple nodes to communicate simultaneously over the same frequency band by carefully canceling the resulting interference. Beamforming and nullforming can also be thought of as basic building blocks for more sophisticated MIMO techniques.
In this work, we present a set of frequency synchronization and phase control algorithms to establish and maintain a VAA for distributed beamforming and nullforming. For frequency-locking, we propose a novel distributed consensus-based algorithm. For a VAA with two nodes, we show that our algorithm achieves frequency lock globally and exponentially with a residual phase disparity that is either 0 or pi. This is in contrast to PLL-like algorithms that only achieve lock locally.
Next, we describe in detail the key ideas behind an implementation of distributed beamforming on a GNU-radio/USRP based software-defined radio (SDR) platform. We introduce a novel DSP-centric Master-Slave (MS) architecture that enables the use of low-rate DSP algorithms for synchronization of high frequency RF signals. We describe the evolution of our implementation from initially using analog signaling with Costas loops/PLLs for frequency offset estimation and compensation, to a digital signaling scheme that uses extended Kalman filters (EKF) to track and compensate for frequency offsets. The EKF-based frequency locking scheme is well-suited for packet wireless networks, e.g., WiFi, ZigBee.
We next consider phase control algorithms for forming beams and nulls with a VAA. In our experimental implementation, we have used several variants of classical 1-bit feedback control algorithm during different stages of our work. 1-bit feedback algorithm is an iterative gradient-ascent algorithm which causes the VAA nodes' signals to add constructively at a designated receiver. We present results to demonstrate the gains in the RSS at the receiver due to beamforming in the real-time settings. We also describe a distributed gradient-descent based algorithm that causes VAA nodes to achieve a null at a designated null target. We provide detailed convergence analysis for the proposed null-steering algorithm. This analysis shows that the algorithm always achieves practical null at null-target; moreover, all the spurious stationary points are locally unstable. Finally, we conclude by providing suggestions for future work.
26
Varughese, Suma. "A Study On Effects Of Phase - Amplitude Errors In Planar Near Field Measurement Facility." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/231.
Анотація:
Antenna is an indispensable part of a radar or free space communication system. Antenna requires different stringent specifications for different applications. Designed and fabricated for an intended application, antenna or antenna array has to be evaluated for its far-field characteristics in real free space environment which requires setting up of far-field test site. Maintenance of the site to keep the stray reflections levels low, the cost of the real estate are some of the disadvantages.
Nearfield measurements are compact and can be used to test the antennas by exploiting the relationship between near-field and far-field. It is shown that the far-field patterns of an antenna can be sufficiently accurately predicted provided the near-field measurements are accurate. Due to limitation in the near-field measurement systems, errors creep in corrupting the nearfield-measured data thus making error in prediction of the far field. All these errors ultimately corrupt the phase and amplitude data.
In this thesis, one such near-field measurement facility, the Planar Near Field Measurement facility is discussed. The limitations of the facility and the errors that occur due to their limitations are discussed. Various errors that occur in measurements ultimately corrupt the near-field phase and amplitude. Investigations carried out aim at a detailed study of these phase and amplitude errors and their effect on the far-field patterns of the antenna. Depending on the source of error, the errors are classified as spike, pulse and random errors. The location of occurrence of these types of errors in the measurement plane, their effects on the far-field of the antenna is studied both for phase and amplitude errors.
The studies conducted for various phase and amplitude errors show that the near-field phase and amplitude data are more tolerant to random errors as the far-field patterns do not get affected even for low sidelobe cases. The spike errors, though occur as a wedge at a single point in the measurement plane, have more pronounced effect on the far-field patterns. Lower the taper value of the antenna, more pronounced is the error. It is also noticed that the far-field pattern gets affected only in the plane where the error has occurred and has no effect in the orthogonal plane. Pulse type of errors which occur even for a short length in the measurement affect both the principle plane far-field patterns.
This study can be used extensively as a tool to determine to the level to which various error such as mechanical, RF etc need to be controlled to make useful and correct pattern predictions on a particular facility. Thereby, the study can be used as a tool to economise the budget of the facility wherein the parameters required for building the facility need not be over specified beyond the requirement. In general, though this is a limited study, it is certainly a trendsetter in this direction.
27
Ingram, David. "An Evaluation of Harmonic Isolation Techniques for Three Phase Active Filtering." Thesis, University of Canterbury. Electrical and Computer Engineering, 1998. http://hdl.handle.net/10092/1260.
Анотація:
Recent advances in power electronics have lead to the wide spread adoption of advanced power supplies and energy efficient devices. This has lead to increased levels of harmonic currents in power systems, degrading the performance of electrical machinery and interfering with telecommunication services. Active filters provide a solution to these problems by compensating for the distorted currents drawn by non-linear loads. Optimal methods for controlling these active filters have been determined by computer simulation and experimental implementation. Methods used for isolating the harmonic content of an unbalanced three phase load current were compared by computer simulations. A technique based on the Fast Fourier Transform (FFT) was developed as part of this work and shown to perform favourably. Notch Filtering, Sinusoidal Subtraction, Instantaneous Reactive Power Theory, Synchronous Reference Frame and Fast Fourier Transform methods were simulated. The methods shown to be suitable for compensation of three phase unbalanced loads were implemented in a Digital Signal Processor to evaluate true performance. These methods were Notch Filtering, Sinusoidal Subtraction, Fast Fourier Transform, and a High Pass Filter based method. A completely digital hysteresis current controller for a three phase active filter inverter has been developed and implemented with a Field Programmable Gate Array. This controller interfaces directly to a digital signal processor and is resistant to electromagnetic interference. Results from the experimental hardware verified that the active filter model used for simulation is accurate, and may be used for further development of harmonic isolation methods. A technique using notch filtering gives the best performance for steady loads, with the FFT based technique giving the most flexible operation for a range of load current characteristics. Novel use of the FFT based harmonic isolation technique allows selective cancellation of individual harmonics, with particular application to multiple shunt filters connected in parallel.
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Kulsreshath, Mukesh Kumar. "Development and study of microdischarge arrays on silicon." Phd thesis, Université d'Orléans, 2013. http://tel.archives-ouvertes.fr/tel-00843656.
Анотація:
The objective of this thesis is to provide a better understanding of various physical phenomena related to microplasmas/microdischarges. For this purpose, arrays of microreactors on silicon were studied. Different array configurations were fabricated to analyse the influence of each parameter on the physical operation of these devices. The present work focuses on the development and characterisation of micro-discharge devices based on silicon. In this thesis, direct current (DC) and alternating current (AC) regimes are studied using different discharge configurations. For the fabrication of these reactors, Silicon wafers are structured and processed in a cleanroom. Fabrication technology used is compatible with the CMOS technology. The microreactors are fabricated with nickel and silicon electrodes, separated by a dielectric layer of SiO2 with a thickness of 6 μm. The thickness of the dielectric is much lower here than the microreactors studied so far. The devices consist of cavities with 25 to 150 μm in diameter. Experiments of the microdischarges are performed in inert gases at a pressure between 100 and 1000 Torr. We first studied the phenomena of ignition and extinction for the microdevices based on alumina. Then, we studied the microreactors based on silicon containing 1 to 1024 cavities under DC and AC regimes. Characteristics of microdischarges were studied by electrical measurements, measurements of optical emission spectroscopy (OES), laser diode absorption spectroscopy (DLAS) and phase resolved optical emission spectroscopy (PROES). These diagnostics allowed us to investigate the phenomena of ignition, extinction, instability and failure mechanisms of the microplasma devices. This thesis work allowed testing the performance and technological limitations of the silicon based microdischarge arrays. Particular attention was paid to their life time.
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Longo, Danilo. "Engineering topological states in arrays of magnetic molecules in interaction with a 2D superconductor." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS224.
Анотація:
Des études récentes ont prédit que l'interaction entre un supraconducteur 2D et du magnétisme local pourrait induire une supraconductivité topologique accompagnée d'états de bord de type Majorana. Pour relever ce défi, nous avons étudié un système basé sur l’interaction entre des auto-assemblages d’aimants moléculaires, tels que les phtalocyanines de manganèse (MnPcs), sur des films minces de plomb (1 et 3 monocouches) épitaxiés sur des surfaces de Si(111) qui montrent une supraconductivité 2D. Nos expériences de Microscopie à effet tunnel (STM) ont révélé que l'adsorption d’une petite quantité de MnPcs sur la monocouche de Pb est accompagnée d’un très faible transfert de charge qui induit une transition de phase structurale macroscopique de la surface elle-même. Les expériences de Spectroscopie à effet tunnel (STS) à 300 mK sur des îlots tricouches de Pb/Si(111) ont montré la présence d'effets non triviaux responsables de la fluctuation spatiale de l’amplitude des pics de cohérence sur des longueurs bien inférieures à la longueur de cohérence supraconductrice. De plus, contrairement à ce qui a été montré sur des monocristaux de plomb, les expériences STS suggèrent que les MnPcs isolées sur des îlots tricouches de plomb se trouvent toujours dans un régime d'interaction faible avec le substrat. L’ensemble de nos résultats, ainsi que l’observation d’une signature spectroscopique localisée sur le bord d’un domaine auto-organisé de MnPcs ouvrent la voie à de futures études sur l’ingénierie des phases topologiques supraconductricesRecent studies predicted that the interaction between a 2D superconductor and local magnetism could induce topological superconductivity accompanied by Majorana edge states. To address this challenge, we have studied a system based on the interaction between self-assemblies of molecular magnets, i.e. manganese phthalocyanines (MnPcs), and thin films of lead (1 and 3 monolayers) grown on Si(111) surfaces that show 2D superconductivity.Our Scanning Tunneling Microscopy (STM) experiments revealed that, adsorption of a tiny amount of MnPcs on a Pb monolayer is accompanied by a very small charge transfer inducing a macroscopic structural phase transition of the surface itself. Scanning Tunneling Spectroscopy (STS) experiments at 300mK on 3 monolayers thick islands of Pb/Si(111) showed the presence of non-trivial effects responsible for the spatial fluctuation of the coherence peaks amplitude on a length scale much smaller than the superconducting coherence length. Furthermore, contrary to what shown on bulk Pb substrates, STS experiments strongly suggest that isolated MnPcs are always found in a weak interaction regime with the 3 monolayers thick Pb islands. Our results together with the observation of an in-gap spectroscopic feature located at the edge of a self-assembled 2D domain of MnPcs pave the route to future studies for the engineering of superconducting topological phases
30
Dallmeyer, Matthew John. "Reducing Fir Filter Costs: A Review of Approaches as Applied to Massive Fir Filter Arrays." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1417544448.
31
Vickerstaffe, Emma. "The development and application of automated multi-step polymer assisted solution phase synthesis for the production of biologically active compound arrays." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614773.
32
Zemba, Michael J. "Site Characterization of Phase Instability via Interferometer Measurement." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1383565461.
33
Scattone, Francesco. "Phased array antenna with significant reduction of active controls." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S168/document.
Анотація:
L'objectif de cette thèse est d'exploiter les phénomènes des ondes de fuite pour améliorer les performances des antennes classiques à ouverture pour les applications spatiales. Ici, nous considérons des configurations planaires où les ondes de fuite sont excitées entre un plan de masse et un superstrat partiellement réfléchissant. Des réseaux de petites ouvertures sur le plan de masse sont utilisés pour alimenter les antennes considérées. Les structures avec superstrat sont développées en configuration réseaux simples ou réseaux à commande de phase, considérées intéressantes en termes de flexibilité du système pour des liens satellitaires de nouvelle génération.Pour étudier efficacement ces antennes, nous avons développé un outil d'analyse basé sur une approche spectrale avec fonction de Green. Cet outil permet d'analyser les structures proposées en prenant en compte l'impact du couplage mutuel entre les éléments sur les performances de rayonnement avec une réduction du temps de calcul et d'utilisation de mémoire.L'augmentation du gain des structures à ondes de fuite peut ouvrir la voie à la réduction du nombre d'éléments des réseaux associés, et donc des commandes en amplitude et phase. Dans une configuration à ondes de fuite, chaque élément du réseau rayonne avec une ouverture équivalente plus grande, augmentant ainsi l'espacement entre les éléments sans affecter le gain global de la structure. Comme largement expliqué dans le manuscrit, les solutions à ondes de fuite représentent par conséquent un avantage majeur pour les antennes du segment utilisateur.En plus de l'amélioration du gain, la technologie à ondes de fuite peut être efficacement exploitée pour synthétiser le diagramme de rayonnement, en choisissant correctement les paramètres de conception de l'antenne. Cette caractéristique peut être utilisée dans les réseaux à commande de phase, pour produire un diagramme d'élément qui minimise les pertes par dépointage et qui filtre les lobes de réseaux. Une procédure de synthèse pour des antennes réseaux raréfiés à ondes de fuite est ainsi présentée dans le manuscrit, ainsi qu'une nouvelle configuration de réseaux avec superstrat irrégulier. Ce dernier permet de réduire les lobes secondaires de l'antenne en utilisant une excitation uniforme. Cette dernière configuration montre clairement que la capacité de modifier le diagramme de rayonnement est la caractéristique la plus attrayante des antennes planaires à ondes de fuite, pour être utilisée dans des solutions de réseaux à commande de phaseThe objective of this thesis is to exploit the leaky-wave phenomena to enhance the performance of classical aperture antennas for space applications. Here, we consider planar configurations where the leaky modes are excited between a ground plane and a partially reflective superstrate. Arrangements of small apertures opening on the ground plane are used to feed the antennas under study. The superstrate-like leaky-wave structures are developed in array or phased array configurations, considered of interest in terms of flexibility of the system for next generation satellite links. In order to efficiently study planar leaky-wave arrays, we have developed an analysis tool based on a Green's function spectral approach. The developed tool allows to precisely analyze the proposed structure by taking into account the impact of the mutual coupling among the elements on the radiation performance of the whole antenna. In addition, it can handle extremely large structures in terms of wavelengths with a small computational effort with respect to commercial tools. In particular, the gain enhancement of leaky-based structures can pave the way to the reduction of the number of elements of the associated phased arrays. In a leaky-wave configuration each element of the array will radiate with a larger equivalent aperture allowing a larger spacing among elements without affecting the final gain of the whole structure. This aspect is particularly important in the case of phased arrays, where phase shifters and control cells are, typically, the most expensive components of the system. As extensively explained in the manuscript, antennas for user segment might find the highest benefit by using leaky-wave solutions. Besides the gain enhancement, the leaky-wave technology can be effectively exploited to conveniently shape the radiation pattern by properly engineering the design parameters of the antenna. This capability can be used in phased arrays to generate a convenient element pattern to minimize the scan losses and filter the grating lobes appearing in the visible space when dealing with periodicities larger than a wavelength. Therefore, a synthesis procedure for thinned leaky-wave arrays is presented in the manuscript. Also, a novel array configuration, the irregular superstrate array, is presented. The irregular superstrate allows the reduction of the side lobes of the antenna below -20 dB in the considered 2.5 % band, using a uniform excitation. This last configuration clearly shows that the shaping capability of leaky-wave antennas is the most appealing feature to be used in phased array solutions
34
Xu, Jian. "X-Band Phase Shifters for Phased Array." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1196888776.
35
Tzanidis, Ioannis. "Ultrawideband Low-Profile Arrays of Tightly Coupled Antenna Elements: Excitation, Termination and Feeding Methods." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316439948.
36
Pudelko, Maciej. "Antigens derived from the mucin MUC1 : Solution and solid-phase synthesis of saccharides, peptides and glycopeptides." Doctoral thesis, Umeå : Department of Chemistry, Umeå Univ, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1630.
37
Eng, Cher Shin. "Digital antenna architectures using commercial off-the-shelf hardware." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FEng.pdf.
Анотація:
Thesis (M.S. in Engineering Science (Electrical Engineering)--Naval Postgraduate School, December 2003.Thesis advisor(s): David C. Jenn, Roberto Cristi. Includes bibliographical references (p. 75-76). Also available online.
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Choudhary, Saumya. "On Plasmonic Superradiance, the Scaling Laws of Spontaneous Parametric Downconversion, and the Principles and Recent Advances in Nonlinear Optics." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35132.
Анотація:
This thesis covers three different topics. The first part is a pedagogical review of the basic principles and recent advances in nonlinear optics. It was originally written as a chapter for the proceedings of the “International School of Physics (Enrico Fermi)” summer school on Photonics held in June, 2014. It is included to provide some background information about nonlinear optical processes in general, and is particularly relevant for the third part of this thesis which is based on the second-order nonlinear optical process of spontaneous parametric downconversion.
The second part is based on original research, and deals with superradiance in plasmonic nanostructures. The process of superradiance, as introduced by Dicke in 1954, entails the shortening of the spontaneous emission lifetime of a collection of N quantum emitters as a consequence of the development of a macroscopic dipole moment. Specifically, the lifetime is shortened by a factor of 1/N, and the linewidth is broadened by a factor of N. Such a linewidth dependence has been previously observed in systems of several plasmonic ‘emitters’. However, a clear physical insight into this phenomenon and how it relates to Dicke superradiance has not been shown yet. In this part, we demonstrate by experiment, simulation, and a simple analytical model that Dicke’s superradiance can indeed be observed in a planar array of plasmonic nanoantennas, with a linewidth that scales linearly with the number of nanoantennas within a square wavelength.
The third part is also based on original research, and is based on the scal- ing laws of spontaneous parametric downconversion (SPDC) for a type-I phase- matching configuration. The variation of bi-photon generation rate, heralding efficiency and radiance with parameters such as crystal length, pump focussing and collection waist sizes are examined for collinear and non-collinear emission. The results can be used to maximize the brightness of the SPDC source or increase the heralding efficiency depending on the application.
39
Franck, Pierre. "Mesoscopic electromagnetic model of carbon-nanotube arrays and scalable technological processes : Application to the fabrication of novel antennasCo-dirigée par Beng Kang Tay." Limoges, 2013. http://aurore.unilim.fr/theses/nxfile/default/6358938e-2b7f-488e-a1d0-6bd8f7e045e6/blobholder:0/2013LIMO4043.pdf.
Анотація:
We report the efforts lead in the design and fabrication of novel antennas from carbon nanotubes (CNTs) to assess their practicality in diverse usage scenarios. CNT-based antennas could help improve the performance of electrically-small antennas but may also allow the development of novel structures such as optically-controlled reflectarrays. They also represent an interesting technology for millimeter-wave and THz applications. Significant progress has been made on each of the four intertwined axes pertaining to these special antennas, modeling, analysis, fabrication and characterization. This has allowed designing and fabricating the first electrically-short CNT antenna prototypes and determining preliminary photocurrent trends. Indeed, we have derived an original mesoscopic model for the electromagnetic properties of aligned arrays of nano-elements with a special focus on CNTs to match simulation and fabrication capabilities. In parallel, we have reproduced and developed CNT growth and deposition techniques and established scalable fabrication processes. Additionally, an analytical model for CNT-based monopole antennas has been derived from transmission line theory. By combining modeling, analysis, simulation and fabrication, we have finally achieved the design and fabrication of CNT-based monopole antenna prototypes. The techniques have also been applied to the fabrication of CNT-based photocurrent samples which have been extensively characterized to highlight optimal illumination conditions and assess expectable performances as a base for future designsNous présentons une étude de faisabilité d’antennes innovantes basées sur les propriétés particulières des nanotubes de carbone (NTC). Celles-ci pourraient permettre une amélioration des performances des antennes électriquement courtes mais aussi le développement de systèmes innovants tels que des réseaux réflecteurs à commande optique. Ce pourrait aussi être une technologie intéressante pour les applications en plein essor dans les domaines des ondes millimétriques et terahertz. Des avancées significatives ont été réalisées suivant les quatre axes interdépendants qui régissent ces antennes : modélisation des NTC, analyse des antennes basées sur les NTC, fabrication à partir de NTC et caractérisation. Ceci nous a permis d’une part de concevoir et de fabriquer les premiers prototypes d’antennes électriquement courtes à base de NTC et d’autre part de mettre en évidence des tendances dans la réponse des NTC sous illumination. En effet, en utilisant une approche mésoscopique, nous avons développé un modèle électromagnétique original pour les ensembles de nano-éléments alignés, en particulier les NTC, permettant leur intégration dans des logiciels de simulation électromagnétique classiques et donc la mise en correspondance des possibilités de fabrication et de simulation. En parallèle nous avons reproduit et développé des méthodes de croissance et de dépôt de NTC et établi des procédés de fabrication pouvant être adaptés à grande échelle. De plus, un modèle analytique des antennes monopôles à base de NTC a été établi à partir d’une approche ligne de transmission. Ces techniques nous ont permis de mettre en avant les compromis nécessaires dans la conception d’antennes de taille réduite à base de NTC et ainsi de concevoir et fabriquer de premiers prototypes. Elles ont aussi été appliquées à la fabrication de structures de test pour une caractérisation des NTC sous illumination. Ceci nous a permis de mettre en évidence les conditions optimales pour générer un courant photoélectrique dans les NTC et d’évaluer les performances pouvant être attendues comme base pour de futurs systèmes
40
Mendes-Simão, Nuno. "Seismicity of the Mid-Atlantic Ridge in the MoMAR area at a regional scale, observed by autonomous hydrophone arrays." Brest, 2009. http://www.theses.fr/2009BRES2033.
Анотація:
Autonomous Hydrophones (AuH) arrays are very excellent to seismically monitor mid oceanic ridges. One of their advantages is the ability of estimating, both for specific array geometries and specific oceanic regions around the globe, the error of the seismic locations. This has been implemented for all the AuH arrays deployed on the Mid-Atlantic Ridge (MAR). Another advantage of the AuH is, its smaller detection threshold. An analysis of the detection thresholds of the AuH that were deployed in the MAR revealed that this feature can greatly impact the number of recorded events, and that this must be considered prior to additional analysis. Transmission Loss analysis shows that the AuH Source Level of an earthquake is mainly due to the conversion from seismic to acoustic energy while the propagation paths play a smaller contribution. An analysis of MAR seismicity reveals that the AuH recorded seismicity mimics the longer time span of teleseismically recorded seismicity and that both are influenced by crustal thermal structure variations along the ridge. AuH recorded seismic clusters are directly linked with teleseismically recorded events and the sections where they occurred are the most active sections of the MAR. Seismicity generally clusters at segment extremities and at the segment scale MBA maxima. Size-frequency and mainshock-aftershock analyses of the clusters reveal that aftershock decay rate is influenced by the mode of faulting. Detachment faults produce seismic sequences with faster decay rate associated with a reduced strain release in comparison to normal faults. This implies the presence of higher levels of serpentinisation on detachment faultsLe principal avantage des réseaux d’AuH, pour la surveillance sismique des dorsales océaniques, est leur faible seuil de détection. Cependant, les variations de seuil de détection entre les réseaux d’AuH déployés au voisinage de Açores, peuvent influencer le nombre de séismes enregistrés. Ces variations doivent donc être analysées avant interprétation de la sismicité. L’amplitude acoustique à la source (SL) d’un séisme dépend surtout de l’efficacité de la conversion séismoacoustique mais aussi, dans une moindre mesure, des effets de propagation. Un autre avantage, la possibilité d’estimer l’erreur de localisation pour différentes géométries des réseaux et de topographie du fond, est présenté pour touts les réseaux d’AuH déployés sur la Dorsale Médio Atlantique (MAR). L’analyse de la séismicité de la MAR montre que la sismicité enregistrée par les AuH ressemble à celle enregistrée par les réseaux à terre au cours des 40 années passées. La distribution spatiale de cette sismicité est liée aux variations du régime thermique de la croute le long de la dorsale. Des essaims de séismes, enregistrés par les AuH, sont liés à des télé-séismes et les sections où ils se produisent sont les plus actives. A l’échelle du segment, les essaims se groupent en extrémité et au voisinage de maxima de la MBA. L’analyse des distributions des SL et du taux de diminution du nombre des répliques indique que les failles de détachement produisent des essaims avec des diminutions plus rapides du nombre des répliques, que les failles normales. Cette observation serait associée à des contraintes plus faibles sur les failles de détachement et impliquerait un niveau de serpentinisation plus important
41
Leonard, Cathy Wood. "Optical feeds for phased array antennas." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80079.
Анотація:
This thesis investigates optical feed methods for phased array antennas. The technical and practical limitations are analyzed and an optimum design is determined. This optimum optical feed is a two-beam interferometric approach which uses acoustooptic phase control. The theory is derived; a computer model is developed; and the limitations are determined. Design modifications are suggested which reduce limitations and greatly extend the range of applications.Master of Science
42
Sanyal, Alarka. "CMOS Phase Shifter for Conformal Phased Array Beamformer Applications." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27697.
Анотація:
A vector modulator based phase shifter is developed using 0.18um CMOS process at S-band frequency to be integrated into a conformal phased array antenna to recover the desired radiation pattern in the entire 360? range. The phase shifter has a variable gain amplifier integrated into the circuit in order to vary gain along with phase for precise control to correct the degraded radiation pattern due to the conformal shaping. The results show state-of-the-art performances including more than 7dB conversion gain with variable feature, a continuous phase rotation of 360? with steps as low as 11.25? and very low power consumption of 17mW, for the first time to the best of the authors? knowledge. The chip size including all pads is 1.5mm X 0.75mm.ND NASA EPSCoR (Agreement FAR0020852)
43
Ng, Kwong-Tai. "Admittance properties of a slot array with parasitic wire arrays in a stratified medium /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259580262744.
44
Ionita, Mihaela-Izabela. "Contribution to the study of synchronized differential oscillators used to controm antenna arrays." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2271/document.
Анотація:
Le travail présenté dans ce mémoire traite de l'étude d'oscillateurs et d'Oscillateurs Contrôlés en Tension (OCT) différentiels couplés appliqués à la commande d'un réseau d’antennes linéaire. Après avoir rappelé les concepts d'antennes réseaux et d'oscillateurs, une synthèse de la théorie élaborée par R. York et donnant les équations dynamiques modélisant deux oscillateurs de Van der Pol couplés par un circuit résonnant a été présentée. Après avoir montré la limitation de cette approche concernant la prédiction de l'amplitude des oscillateurs, une nouvelle formulation des équations non linéaires décrivant les états de synchronisation a été proposée. Néanmoins, compte tenu du caractère trigonométrique et fortement non linéaire de ces équations, une nouvelle écriture facilitant la résolution numérique a été proposée. Ceci a permis l'élaboration d'un outil de Conception Assistée par Ordinateur (CAO) fournissant une cartographie de la zone de synchronisation de deux oscillateurs de Van der Pol couplés. Celle-ci permet de déterminer rapidement les fréquences d'oscillation libres nécessaires à l'obtention du déphasage souhaité. Pour ce faire, une procédure de modélisation de deux oscillateurs et OCTs différentiels couplés, par deux oscillateurs de Van der Pol couplés par une résistance a été élaborée. Les résultats fournis par l'outil de CAO proposé ont ensuite été comparés avec les résultats de simulations de deux oscillateurs et OCTs différentiels couplés obtenus avec le logiciel ADS d'Agilent. Une très bonne concordance des résultats a alors été obtenue montrant ainsi l'utilité et la précision de l'outil présentéThe work presented in this thesis deals with the study of coupled differential oscillators and Voltage Controlled Oscillators (VCO) used to control antenna arrays. After reminding the concept of antenna arrays and oscillators, an overview of R. York's theory giving the dynamics for two Van der Pol oscillators coupled through a resonant network was presented. Then, showing the limitation of this approach regarding the prediction of the oscillators' amplitudes, a new formulation of the nonlinear equations describing the oscillators' locked states was proposed. Nevertheless, due to the trigonometric and strongly non-linear aspect of these equations, mathematical manipulations were applied in order to obtain a new system easier to solve numerically. This has allowed to the elaboration of a Computer Aided Design (CAD) tool, which provides a cartography giving the frequency locking region of two coupled differential Van der Pol oscillators. This cartography can help the designer to rapidly find the free-running frequencies of the two outermost differential oscillators or VCOs of the array required to achieve the desired phase shift. To do so, a modeling procedure of two coupled differential oscillators and VCOs as two coupled differential Van der Pol oscillators, with a resistive coupling network was performed. Then, in order to validate the results provided by our CAD tool, we compared them to the simulation results of two coupled differential oscillators and VCOs obtained with Agilent’s ADS software. Good agreements between the simulations of the circuits, the models and the theoretical results from our CAD tool were found
45
Ong, Chin Siang. "Digital phased array architectures for radar and communications based on off-the-shelf wireless technologies." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FOng.pdf.
Анотація:
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2004.Thesis advisor(s): David C. Jenn, Siew Yam Yeo. Includes bibliographical references (p. 63-64). Also available online.
46
Kim, Sunghwan. "Phase shifter approaches for compact low-power phased array transmitters." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3398530.
Анотація:
Thesis (Ph. D.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed May 5, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 103-109).
47
Yang, Zhenchao. "High-Efficiency Passive and Active Phased Arrays and Array Feeds for Satellite Communications." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5741.
Анотація:
Satellite communication (Satcom) services are used worldwide for voice, data, and video links due to various appealing features. Parabolic reflector antennas are typically used to serve a cost effective scheme for commercial applications. However, mount degradation, roof sag, and orbital decay motivate the need for beam steering. Limited scan range beam steering opens a third option for electronic beam steering with lower cost than full aperture phased arrays and higher tracking speed and accuracy than mechanical-only steering.Multiple high efficiency passive patch array feeds were designed, fabricated, and measured, including a 2x2 MSA array, a stacked shorted annular patch antenna, and an SIW-fed hexagonal array feed based on PTFE material, achieving performance comparable to a horn feed. For multiband dual polarization applications, passive MSA feed solutions are also provided. Multiple MSA array feeds with high isolation were designed for dual band dual polarization applications. More functionality can be realized with multi-layer PCB techniques for complex communication scenarios.Limited scan range electronic beam-steering with a parabolic reflector fed by an active array feed which only needs gain control was demonstrated experimentally, leading to a low cost and effective solution for active beam scanning. A cost-effective flat-panel phased array with limited scan range electronic beam-steering was proposed by tiling high efficiency 4x4 passive subarrays and performing beam scanning at the tile level. The sidelobe issue was also investigated to comply with the pattern mask requirement set by FCC.To enable better use of circularly polarized (CP) MSAs for electronically beam-formed antenna systems, the impact of mutual coupling on the performance of high-sensitivity dual-polarized receivers for satellite communications applications was analyzed. A new analysis method for intrinsically dual-CP MSAs based on an equivalent circuit model and Jones matrices was proposed and validated to overcome the port isolation challenge. The model provides accurate estimates of impedances and S-parameters, as well as field parameters such as axial ratio. The feasible region for XPI and impedance mismatch factor is found for dual CP antennas. The circuit model enables multiple useful applications. Effective decoupling and matching schemes was proposed and demonstrated, leading to a high isolation, good match, and wide AR bandwidth dual CP MSA for satellite communications.
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Mellouli, Moalla Dorra. "Étude comportementale et conception d'un réseau d'oscillateurs couplés intégré en technologie silicium appliqué à la commande d'un réseau d'antennes linéaire." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2332/document.
Анотація:
Le travail présenté dans ce mémoire traite de l’étude comportementale, de la conception et de la validation d’une nouvelle architecture, basée sur le couplage d’O.C.T différentiels, appliquée à la commande électronique de l’orientation du diagramme de rayonnement d’un réseau d’antennes linéaire. Après avoir optimisé la structure de l’O.C.T différentiel, qui constitue le corps du circuit de commande, selon une méthode graphique qui visualise les différentes contraintes imposées par le système afin de minimiser son bruit de phase et sa consommation, l’O.C.T à sorties différentielles a été réalisé en technologie NXP BiCMOS SiGe 0,25 μm puis mesuré en boîtier. Etant donné que la direction de rayonnement d’une antenne réseau dépend de la valeur du déphasage imposé entre les signaux envoyés sur deux antennes adjacentes, les équations théoriques modélisant deux O.C.T couplés et permettant d’extraire les amplitudes et le déphasage entre les différents signaux ont été décrites. La dernière étape a alors consisté en la réalisation de deux réseaux constitués respectivement de deux et de quatre O.C.T couplés au moyen d’une résistance puis d’un transistor MOS fonctionnant en zone ohmique. L’approche de couplage proposée a été validée en se basant sur les résultats de mesures effectués. De plus, l’impact de l’utilisation de structures différentielles sur la plage de déphasage obtenue et donc sur le dépointage réalisé a également été présenté ce qui nous a permis de conclure sur l’efficacité du circuit de commande proposéThe work presented in this thesis deals with the study, design, and validation of a new architecture based on the coupling of differential voltage controlled oscillators (VCO) applied to the beamsteering of a linear antenna array. After optimizing the differential VCO structure, with a graphical optimization approach while satisfying design constraints imposed, in order to minimize the phase noise and power consumption, the differential VCO was realized in NXP BiCMOS SiGe 0.25 µm process and then measured. Since the radiation direction of an antenna array depends on the phase difference imposed between the two signals on adjacent antennas, the theoretical equations modeling two coupled VCOs, and allowing the extraction of the amplitude and phase difference between the outputs signals have been presented. The last step was the realization of two arrays consisting respectively of two and four VCOs coupled through a resistor and a MOS transistor operating in the triode region. The proposed coupling approach is validated based on the obtained measurement results. Furthermore, the impact of the use of differential structures on the phase shift range obtained and thus on the beam-scanning range achieved was also presented allowing to conclude on the efficiency of the proposed architecture
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Charles, Cameron T. "A calibrated phase and amplitude control system for phased-array transmitters /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/5911.
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Jaeck, Vincent. "Développement d’antennes de communication reconfigurables en bande C pour munitions intelligentes." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S104/document.
Анотація:
De nos jours, les communications sans fil sont devenues un moyen incontournable et universel d'échange d'un large éventail d'informations entre différents systèmes, certains d'entre eux étant en mouvement comme des drones parmi tant d'autres. Dans le contexte de cette thèse nous considérons une liaison entre un projectile et une station de base. La géométrie de la structure ainsi que les contraintes aérodynamiques d'un tir balistique impliquent l'utilisation d'antennes patchs dans la partie conique à l'avant du projectile. Ce type d'antenne est facile à intégrer à une plate-forme en tant que réseau conformé tout en respectant les contraintes d'encombrement. Ces communications doivent être fiables et discrètes dans un environnement perturbé ou hostile. Les diagrammes de rayonnement du réseau d'antennes doivent présenter des caractéristiques spécifiques, notamment dans le cas particulier d'objets volants et possédant une rotation en roulis (rotation autour de son axe) qui impliquent l'utilisation d'un réseau phasé et commuté par rapport à sa position. Une antenne qui présenterait un rayonnement fixe assurerait une liaison avec un interlocuteur, mais rayonnerait également dans d'autres directions sensibles ce qui pourraient interférer avec la communication principale. La solution qui consiste à activer et désactiver des sous-réseaux verticaux afin d'orienter le lobe principal dans la plan orthogonal à la pointe semble être en accord avec les contraintes de la structure tournante. Un réseau conique a été étudié puis 2 prototypes ont été fabriqués, dont un à l'ISL. Les sous-réseaux sont répartis de manière égale autour de la pointe de façon à pouvoir rayonner dans toutes les directions. De plus, chaque sous-réseau est composé de trois éléments ce qui permet d'orienter également le lobe principal dans le plan longitudinal de la pointe (le long de l'axe du projectile) grâce à un dépointage électronique. Un système électronique de formation de faisceaux a été développé dans le but de contrôler 12 éléments rayonnants. Le réseau d'antennes ainsi que le circuit de répartition ont été caractérisés dans un premier temps de manière indépendante afin d'optimiser les lois de phase nécessaires à dépointer le lobe à partir des pondérations mesurées. Au final, le réseau de 12 éléments associé à son système d'alimentation dédié a été mesuré dans les chambres anéchoïques de DGA-MI et de l'ISL et les mesures sont en accord avec les simulationsNowadays wireless communications have become a useful and universal mean to exchange a wide range of information between different systems, some of them being moving, as UAVs among others. In this context we consider here the link between a projectile and a base station. The shape of the structure and the aerodynamic constraints involve the use of patch antennas in the conical front part. This class of antenna is easy to be integrated into the platform as a conformal array, while respecting space constraint. Communications have to be reliable and discrete in disturbed or hostile environment. Antennas array radiation patterns must have some specific characteristics, in particular in the case of flying objects with spin which involves the use of a switched phased array considering its roll position. A fixed-radiation pattern antenna may presents a relevant level or gain toward the interlocutor, but also toward sensitive directions, in which may be located others systems, interfering with the current communication. The solution to switch on and off vertical sub-arrays to steer the beam in the azimuthal plane seem convenient ant fitting the requirements of rotating platform. A conical phased array was studied and two prototypes were manufactured, one at ISL. Sub-arrays are distributed around the conical shape in order to be able to radiate in each direction. Moreover, each sub-array are composed of three radiating elements allowing to steer the main antenna beam in many direction (along the projectile fuze axes). A beam forming network was developed to control the 12 radiating elements conical array. The antenna array and the feeding network were characterized independently in order to optimized the phase of each radiating element. Finally, measurements were done on the whole system in the DGA-MI and ISL anechoic chambers and are in good agreement with simulation results