Dissertations / Theses on the topic 'Microstrip Ring Antennas'

In this study we tried to design a microstrip antenna, to get a suitable radiation pattern for a LEO satellite. Our aim is to get a radiation pattern that has a maximum power which is not in the broadside direction to the antenna surface
instead broadside radiation has a relatively lower power density. Maximum power radiation is desired to be at about 30 &ndash
50 degrees angle beyond the normal to the antenna surface. We desire circularly polarized radiation. We used two concentric antennas
one is a circular patch at the center and the other is an annular ring which is used at the outer region. By using Ansoft Ensemble 8.0 software, we design an antenna which has a resonance frequency at 8.2 GHz. Using the result of the program we design the real antenna. The measurement results are compared with the simulation results.

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Universidade Federal do Rio Grande do Norte
Metamaterials have attracted a great attention in recent years mostly due to their electromagnetic properties not found in nature. Since metamaterials began to be synthesized by the insertion of artificially manufactured inclusions in a medium specified host , it provides the researcher a broad collection of independent parameters such as the electromagnetic properties of the material host. In this work was presents an investigation of the unique properties of Split Ring Resonators and compounds metamaterials was performed. We presents a theoretical and numerical analysis , using the full-wave formalism by applying the Transverse Transmission Line - LTT method for the radiation characteristics of a rectangular microstrip antenna using metamaterial substrate, as is successfully demonstrated the practical use of these structures in antennas. We experimentally confirmed that composite metamaterial can improved the performance of the structures considered in this thesis
Os metamateriais tem atra?do uma grande aten??o nas ?ltimas d?cadas, principalmente devido as suas propriedades eletromagn?ticas n?o encontradas na natureza. Desde que os metamateriais passaram a ser sintetizados atrav?s da inser??o de inclus?es artificialmente fabricadas num meio hospedeiro especificado, isto propicia ao pesquisador uma larga cole??o de par?metros independentes, tais como as propriedades eletromagn?ticas do material hospedeiro. Neste trabalho foi realizada uma investiga??o das propriedades ?nicas dos Ressoadores em Anel Partido (Split Ring Ressonators - SRR) e dos metamateriais compostos. Apresentou-se uma an?lise te?rica e num?rico-computacional, utilizando o formalismo de onda completa atrav?s da aplica??o do m?todo da Linha de Transmiss?o Transversa LTT, para as caracter?sticas ressonantes de uma antena de microfita com patch retangular utilizando substrato metamaterial, assim como ? demonstrado com sucesso ? utiliza??o pr?tica dessas estruturas em antenas. Esta utiliza??o pr?tica ? confirmada experimentalmente

Microstrip antennas are low in profile, light in weight, conformable in structure and are now developed for many applications. The main difficulty of the microstrip antenna is its narrow bandwidth. Several modern applications like satellite communications, remote sensing and multi-function radar systems will find it useful if there is dual band antenna operating from a single aperture. Some applications require covering both transmitting and receiving frequency bands which are spaced apart. Providing multiple antennas to handle multiple frequencies and polarizations becomes especially difficult if the available space is limited as with airborne platforms and submarine periscopes. Dual band operation can be realized from a single feed using slot loaded or stacked microstrip antenna or two separately fed antennas sharing a common aperture. The former design, when used in arrays, has certain limitations like complicated beam forming or diplexing network and difficulty to realize good radiation patterns at both the bands. The second technique provides more flexibility with separate feed system as beams in each frequency band can be controlled independently. Another desirable feature of a dual band antenna is easy adjustability of upper and lower frequency bands. This thesis presents investigation of a new dual band antenna, which is a hybrid of microstrip and waveguide radiating elements. The low band radiator is a Shorted Annular Ring (SAR) microstrip antenna and the high band radiator is an aperture antenna. The hybrid antenna is realized by forming a waveguide radiator in the shorted region of the SAR microstrip antenna. It is shown that the upper to lower frequency ratio can be controlled by the proper choice of various dimensions and dielectric material. Operation in both linear and circular polarization is possible in either band. Moreover, both broadside and conical beams can be generated in either band from this antenna element. Finite Element Method based software, HFSS and Method of Moments based software, FEKO were employed to perform parametric studies of the proposed dual band antenna. The antenna was not tested physically. Therefore, in most cases, both HFSS and FEKO were employed to corroborate the simulation results.
Master of Science

In recent years there has been a growing demand for reduced mass, small launch volume, and, at the same time, high-gain large-aperture antenna systems in modern space-borne applications. This dissertation introduces new techniques for dual-band reflectarray antennas to meet these requirements. A series of developments is presented to show the dual-band capability of the reflectarray. A novel microstrip ring structure has been developed to achieve circular polarization (CP). A C/Ka dual-band front-fed reflectarray antenna has been designed to demonstrate the dual-band circular polarized operation. The proposed ring structure provides many advantages of compact size, more freedom in the selection of element spacing, less blockage between circuit layers, and broader CP bandwidth as compared to the patches. An X/Ka dual-band offset-fed reflectarray is made of thin membranes, with their thickness equal to 0.0508 mm in both layers. Several degrading effects of thin substrates are discussed. To overcome these problems, a new configuration is developed by inserting empty spaces of the proper thickness below both the X and Ka band membranes. More than 50 % efficiencies are achieved at both frequency ranges, and the proposed scheme is expected to be a good candidate to meet the demand for future inflatable antenna systems. An X/Ka dual-band microstrip reflectarray with circular polarization has also been constructed using thin membranes and a Cassegrain offset-fed configuration. It is believed that this is the first Cassegrain reflectarray ever developed. This antenna has a 0.75-meter-diameter aperture and uses a metallic sub-reflector and angular-rotated annular ring elements. It achieved a measured 3 dB gain bandwidth of 700 MHz at Xband and 1.5 GHz at Ka-band, as well as a CP bandwidth (3 dB axial ratio) of more than 700 MHz at X-band and more than 2 GHz at Ka-band. The measured peak efficiencies are 49.8 % at X-band and 48. 2 % at Ka-band. In summary, this dissertation presents a series of new research developments to support the dual-band operation of the reflectarray antenna. The results of this work are currently being implemented onto a 3-meter reflectarray with inflatable structures at the Jet Propulsion Laboratory and are planned for other applications such as an 8-meter inflatable reflectarray in the near future.

In this thesis two different research topics are undertaken, both in the area of compact RF/microwave circuits design. The first topic involves the design of a compact circularly polarized (CP) slot-ring antenna. A study of several compact CP microstrip and slotline antennas reported in the past has been carried out. In this research, a method of reducing the size of a printed slot-ring antenna is proposed. The reduction in size is achieved by introducing meandered-slot sections in the ring. Circular polarization is achieved by introducing an asymmetry, also a meandered-slot section, and feeding the antenna at an angle of 45o from the asymmetry using a microstrip feed line. The minimum axial ratio of 0.4 dB is obtained at 2.46 GHz, which is the operating frequency of the antenna. The size of the proposed antenna is reduced by about 50% compared to a conventional CP slot-ring antenna and it displays a CP bandwidth of about 2.5%. The simulated and measured results are presented, and they are in good agreement. The small size of the antenna makes it very suitable for use in modern RF/microwave wireless systems which require compact, low cost, and high performance circuits. Moreover, its CP behavior makes it more attractive for applications such as satellite communications. The second topic in the thesis involves the design of a compact microstrip bandpass filter using triangular open-loop resonators. A new compact three-pole microstrip bandpass filter using four triangular open-loop resonators is presented. A fourth resonator is placed to provide cross-coupling in the structure which gives a better skirt rejection. The measured pass-band center frequency is 2.85 GHz. The filter demonstrates about 7% bandwidth with insertion loss of less than 1 dB in the passband, a return loss of greater than 15 dB and out-of-band rejection of greater than 30 dB. The simulated and measured results are in good agreement. The proposed filter is very attractive for use in modern wireless systems which require bandpass filters having compact size, low insertion loss, high selectivity, and good out-of-band rejection.

In this research we attempted several modifications to microstrip ring/loop antennas to design multi-frequency antennas through systematic approaches. Such multi-frequency antennas can be useful while building compact terminals to operate at multiple wireless standards. One of the primary contributions was the use of a capacitive feed arrangement that enables simultaneous excitation of multiple concentric rings from an underlying transmission line. The combined antenna operates in the same resonant bands as the individual rings and avoids some of the bands at harmonic frequencies. A similar feeding arrangement is used to obtain dual band characteristics from just one ring, with improved bandwidth. This is made possible by widening two adjacent sides of a square ring antenna symmetrically, and attaching an open stub to the inner edge of the side opposite to the feed line. Use of fractal segments replacing the side with the stub also results in a similar performance. Use of fractal geometries has been widely associated with multi-functional antennas. It has been observed from the parametric studies that, the ratio of the resonant frequencies can range from 1.5 to 2.0. This shows some flexibility in systematically designing dual-band antennas with a desired pair of resonant frequencies. An analysis technique based on multi-port network modeling (MNM) has been proposed to accurately predict the input characteristics of these antennas. This approach can make use of the ordered nature of fractal geometries to simplify computations. Several prototype antennas have been fabricated and tested successfully to validate simulation and analytical results.

In this research we attempted several modifications to microstrip ring/loop antennas to design multi-frequency antennas through systematic approaches. Such multi-frequency antennas can be useful while building compact terminals to operate at multiple wireless standards. One of the primary contributions was the use of a capacitive feed arrangement that enables simultaneous excitation of multiple concentric rings from an underlying transmission line. The combined antenna operates in the same resonant bands as the individual rings and avoids some of the bands at harmonic frequencies. A similar feeding arrangement is used to obtain dual band characteristics from just one ring, with improved bandwidth. This is made possible by widening two adjacent sides of a square ring antenna symmetrically, and attaching an open stub to the inner edge of the side opposite to the feed line. Use of fractal segments replacing the side with the stub also results in a similar performance. Use of fractal geometries has been widely associated with multi-functional antennas. It has been observed from the parametric studies that, the ratio of the resonant frequencies can range from 1.5 to 2.0. This shows some flexibility in systematically designing dual-band antennas with a desired pair of resonant frequencies. An analysis technique based on multi-port network modeling (MNM) has been proposed to accurately predict the input characteristics of these antennas. This approach can make use of the ordered nature of fractal geometries to simplify computations. Several prototype antennas have been fabricated and tested successfully to validate simulation and analytical results.

博士
國立中山大學
電機工程研究所
83
Two conformal structures of spherical and cylindrical annular- ring microstrip antennas are studied in this dissertation. Most of the studies are concentrated on the spherical annular-ring microstrip structures and are performed by using a Green''s- function formulation in the spectral domain and a Galerkin''s moment-method calculation. Besides these studies, I also analyzes the cylindrical annular-ring microstrip antenna using a cavity-model analysis. The resonance problem of a spherical annular-ring microstrip structure is first investigated. The numerical convergence of the complex resonant frequency calculation using different numbers of basis functions is discussed. Effects of the curvature on the resonant frequency and the quality factor are also analyzed and discussed. With the presence of superstrate loading, a significant effect on the resonant frequency and the quality factor is observed. Another structure with an air gap between the substrate and the ground sphere is also shown. Results indicate that the bandwidth increases due to the existence of an air gap. The excitation problem of a spherical annular-ring microstrip antenna is also investigated. A coaxial probe feed is used as an excitation source. Numerical results of the input impedance, cross-polarized field, and surface current distribution on the annular-ring patch are calculated and analyzed. For the purpose of improving the bandwidth of the microstrip antenna, another novel geometry of a spherical- circular microstrip antenna with a parasitic annular-ring patch is studied. The input impedance at the driven circular disk is formulated and calculated, and the results for the VSWR are presented. It is found that, by choosing a proper gap spacing between the circular disk and the annular-ring patch, the antenna bandwidth of the spherical- circular microstrip antenna is considerably increased.

碩士
建國科技大學
機電光系統研究所
93
This proposal presents the designs of a single-feed ring microstrip antenna with circular polarization (CP). Because the ring microstrip antenna has a smaller patch size comparing to the other shapes of microstrip antenna for a fixed operating frequency, it is attractive for the present wireless system. The proposal is mainly divided into three topics. First, for an annular-ring microstrip antenna, the CP radiation is excited by placing a L-shaped strip connected to two orthogonal sides of the inner boundary of the annular-ring patch. Secondly, the corner-trnucated technique is applied to a square-ring microstrip antenna. When the square-ring microstrip antenna with a narrow ring strip and thick substrate would be encountered the problem of the impedance missmatch. The impedance problem can be solved by the two technologies: using capacitively coupling feed and changing the inner slot size. Finally, the effects of the superstrate on the CP performance for the square-ring microstrip antennas are studied experimentally. All of the simulated results for the studied antennas, such as 10-dB return loss, impedance bandwidth, and 3 dB CP bandwidth obtained from the electromagnetic software IE3DTM , will be compared with the experimental results.

碩士
逢甲大學
電機工程所
101
Recently, it is a pre-requisite requirement for hand-held communication products to possess the advantages such as light in weight, compact size and low manufacturing cost. To satisfy these requirements, a single structure design that comprised of an antenna integrated with the front-end circuit of the communication system is presently attracting many attentions. However, higher-order resonant modes excited by the antenna can cause EMI problems on the active circuit, which lead to degrading the performances of the system. Hence, the common solution to solve this problem is to use low-pass or band-pass filter. However, this method will increase the circuit size, manufacture cost, and insertion loss. To resolve these disadvantages, harmonic suppression antenna design is now an attractive topic of research interest. This thesis are divided into two parts, the first part presents a harmonic suppression annular-ring slot antenna that operates in the 2.4 GHz WLAN band. Here, the inverted U-shaped ground defect structure (DGS) is used as a low-pass filter, and it is integrated into an annular-ring slot antenna, so that it can suppress unwanted higher-order resonance modes (return loss < 3 dB) within the frequencies range between 3 and 9 GHz. In the second part of this thesis, a circularly polarized (CP) annular-ring slot antenna with harmonic suppression is proposed. It is noteworthy that this CP annular-ring slot antenna with harmonic suppression design has never been discussed or reported elsewhere in the open-literature. In this design, a novel CP annular-ring slot antenna operating at WLAN 2.4 GHz is initially studied with axial ratio (AR) bandwidth of 210 MHz (8.79%). Here, the main advantage of this CP slot antenna design is that during the process of integration with the harmonic suppression structure (DGS) discussed in the part 1, there is no need to alter the antenna’s feed terminal. By integrating the DGS into the proposed CP annular-ring slot antenna structure, a 2.4 GHz WLAN antenna with wide harmonic suppression bandwidth between 3 and 10 GHz is achieved, and the AR bandwidth is 223 MHz (9.33%).

碩士
逢甲大學
電機工程學系
106
Recently, it is a prerequisite requirement for hand-held communication products to possess the advantages such as light in weight, compact size and low manufacturing cost. To satisfy these requirements, a single structure design that comprised of an antenna integrated with the front-end circuit of the communication system is presently attracting many attentions. However, high order harmonic modes excited by the antenna can cause electromagnetic interference (EMI) problems on the active circuit, which lead to degrading the performances of the system. Hence, the common solution to solve this problem is to use low-pass or band-pass filter. However, this method will increase the circuit size, manufacture cost, and insertion loss. To resolve these disadvantages, antenna design with harmonic suppression is now an attractive topic of research interest. This thesis is divided into two parts, the first part presents a wide band harmonic suppression circular ring slot antenna that operate in the 2.45 GHz wireless local area network (WLAN) band. Here, a novel stepped impedance resonator (SIR) structure as a low-pass filter and the open stubs (OS) as a band-stop filter are integrated into the circular ring slot antenna, so that it can suppress unwanted high order harmonic modes (return losses < 3 dB) within the frequencies range from 3 to 20 GHz. Also, it is well known the conventional ring slot antenna is a half wavelength resonator whereas the SIR structure is not only regarded a LPF but also can reduce the size of antenna about 15 % by its electrical characteristic. In the second part of this thesis, a triple-band circular ring slot antenna with wideband harmonic suppression is proposed. It is noteworthy that this triple-band circular ring slot antenna with wideband harmonic suppression design has no effect on the fundamental resonate mode with etching extra slots, so that can operate in the 2.4 GHz, 5.2 GHz and 5.8 GHz WLAN application.

To meet the demand of continuously growing RF and microwave technologies, scientists and engineers have developed innovative materials consisting of conducting and dielectric materials that overcome limitations in the properties of natural materials. Over the last decades, the development of these artificial materials has evolved to be a new field. An artificial material is a synthesized material that gains its electromagnetic properties from its structure rather than inheriting them directly from those it is composed of. Planar versions of these artificial materials are often characterized by small periodic conducting patches over a dielectric substrate. In addition to the periodicity, the interaction of these structures with the electromagnetic waves depends on the shape and size of the small patches. Planar artificial materials pursued in electromagnetics include frequency selective surfaces (FSS), high impedance surfaces (HIS), artificial magnetic conductors (AMC), and electromagnetic bandgap (EBG) materials, which are characterized by periodic unit cells whose lattice constant is comparable with the operational wavelength. One of the very commonly seen geometry is the mushroom structure, which has a patch array with each element connected to the metal on the other side of the dielectric with a via. These metalbacked configurations are used in various antenna applications. Some narrowband absorbers have also been suggested using these configurations. This thesis investigates new artificial materials consisting of one- and two- layer of metal patch arrays that overcome the requirement for vias, and examines their design and analysis for four different applications (i) Circularly polarized antennas (ii) Surface wave suppression of microstrip antennas (iii) In-phase reflection surface and (iv) Thin radar absorbing material. Artificial materials with square patch arrays with or without vias can be designed as artificial magnetic conductors. Arrays of rectangular patches with vias or square patches with two vias or slots have been proposed for polarization sensitive reflectivity characteristics. In this thesis we propose a simple geometry for polarization sensitive reflection characteristics. This consists of a modification to square patches with variants of fractal Minkowski curves as boundaries on two of its sides, printed over a metal backed dielectric substrate without vias. The structure is compact, and due to its planar nature, it can be fabricated easily using planar technology. Properties and performance of the structure is analyzed numerically through simulations by varying fractal properties of the sides. The asymmetry in the patch causes the reflection phase of the proposed structure to depend on the polarization state of the incident wave and frequency. A phase difference above 200 degrees between the x- and y-polarized reflected waves has been achieved with small unit cells. Application of the proposed via-less structure to generate circular polarization using simple dipole antenna is also demonstrated in this thesis. Square patches arrays with vias have been proposed as high impedance surfaces (HIS) with in-phase reflection and as electromagnetic bandgap (EBG) structures for suppressing surface waves in microstrip antenna applications. The second structure proposed in this thesis is an alternative for these mushroom structures, and consists of a periodic array of square metal patches (on the top surface) and square metal rings (embedded within the dielectric substrate). This structure does not require any vias for effective operation and is analyzed extensively by numerical simulations. In-phase reflections due to high surface impedance and surface-wave suppression characteristics similar to the mushroom structure proposed by Sievenpiper have been validated. Application of the structure to reduce mutual coupling between microstrip antennas and to improve the radiation pattern are demonstrated through simulations. The structure is fabricated and experimental measurements have been made to confirm surface wave suppression characteristics. A waveguide-based experiment was done to demonstrate the in-phase reflection characteristics. One of the main advantages of the proposed structure is that it is planar in nature and easily fabricated using planar technology, without the need for any via connections across dielectric layers. Another feature is that it exhibits in-phase reflection and surface wave suppression bands at the same frequency band as in mushroom structure. The scalability of this structure to operate in different frequency ranges is also demonstrated in this thesis. Modifications to EBG using either resistive patches or surface mounted resistors have been used as absorber. In this thesis, we propose the use of the above ring-patch structure printed on a moderately lossy substrate such as FR4, as a near-perfect electromagnetic absorber. It is demonstrated that input impedance of the structure can be configured to match the free space impedance by varying the width of the ring to result in near-perfect absorption. This configuration causes a concentration of electric fields in the dielectric region between the ring and patch, thereby enhancing the dissipation of the energy. Monostatic and Bistatic radar cross section measurements have been used to ensure that there are no scattered fields in other directions. The structure is thin, easy to fabricate, and is scalable to operate at different frequencies. This does not use any resistive materials for absorption. It is shown that 99% of the incident power is dissipated by either dielectric or metal losses. The performance of this structure is analyzed using an equivalent circuit approach. A method for improving the bandwidth of this absorber by combining four unit cells and optimizing the dimensions of this sub-array is also proposed here. The performance of this EBG based absorber configuration is similar to the metamaterial based absorbers proposed recently with much smaller unit cells. To summarize, this thesis investigates electromagnetic behavior of single and stacked twolayer periodic metal patches without any interconnects, which are simple and easy to fabricate using planar approaches. It has been established that the configurations proposed in this thesis are equally effective for various electromagnetic applications as previously reported geometries, often characterized by vias or surface mount components.

碩士
國立彰化師範大學
電機工程學系
95
The designs of a reconfigurable ring patch antenna are proposed and studied in this dissertation. The thesis is mainly divided into three topics. First, the design of a ring patch antenna with wideband and dual-frequency operations is presented. The antenna consists of a parasitic square ring patch that is shorted to the ground plane through two shorting walls and is excited by a top-loaded coaxial probe. For the proposed design, while the side length of the square ring patch is about 0.3 free-space wavelengths and the antenna height is less than 0.1 free-space wavelengths, a 10 dB-input-impedance bandwidth of more than 50 % can be achieved. Also, the antenna can provide stable monopole-like conical radiation patterns across the impedance bandwidth. In addition, it is also found that two different resonant modes, patch-loaded monopole mode and normal patch mode, can be simultaneously excited in the shorted patch antenna structure by a coupling rectangular strip inside the ring patch. The antenna can radiate monopole-like and broadside patterns at the two operating frequencies, respectively. Second, a reconfigurable patch antenna with the functions of switchable radiation patterns, and polarizations is presented. The antenna is composed of a ring patch and four shorting walls. By controlling the connections states between the ring patch and shorting walls through pin diodes, the antenna can be operated at different modes to achieve the switching of the radiation patterns and polarizations. Moreover, three pairs of the shorting walls with various widths are integrated into the antenna to excite the patch-load monopole mode, and the resonant frequency can be changed by activating various pair of the shorting walls. From the obtained results, the three operating frequencies can occupy a successive impedance bandwidth, which makes the antenna with wide band operation.

碩士
中正理工學院
電機工程研究所
86
Recently,the communication equipments are widely used in the development of global communication. In application, these equipments adopt the microwave band for operation. Thus, the microwave circuits play a important role in modern microwave communication. Mainly, a small-size,low-cost higher-frequency and low-loss microwave circuit are necessary in practice. Generally, simplified the microwave circuit are available for small-size and low-cost. In this thesis, we proposed a method to have an alternative microstrip antenna designated active microstrip antenna. It can represent the LNA, OSC and Mixer of the conventional superheterdyn receiver in all. It is found the present method can be applied in radar and microwave systems.

碩士
中華技術學院
電子工程研究所碩士班
94
A dual-band broadband annular-ring slot microstrip antenna is designed. Its structure is simple. This antenna is analyzed and optimized by using the IE3D software. The annular-ring slot and coupled microstrip feed-line are built on the FR4 printed board. The two resonant frequencies of the proposed antenna are decided by the redius of the annular-ring slot. The prototype are fabricated and measured. The two resonant frequencies are 2.4GHz and 5.8GHz. At 2.4GHz, input impedance bandwidth is23.4% for the S11 < -10 dB, with the peak gain on the order of 8.6dBi. At 5.8GHz, input impedance bandwidth is 13.7% for the S11 < -10 dB, with the peak gain on the order of 14dBi. It is suitable for WLAN applications.

碩士
中原大學
電機工程研究所
100
Abstract For this thesis, we use a Zeland Analysis Software IE3D to design a circular polarization microstrip antenna. We used low-cost materials to design a microstrip antenna and made use of it to easily assemble the structure and to conveniently move it around. As a result, we replace the inconvenience of using large helical antenna motor rack receiver. Thus, we came up with the subject of making an application in satellite signal reception. In this thesis, we propose several key points: for the first part, we deal with selection of materials. In accordance with the circular polarization microstrip antenna’s theory and equations, we use the Zeland Analaysis Software IE3D to simulate circular polarization microstrip antenna. In order to achieve the special features of the stimulation of circular polarization of antenna, the antenna feed design uses single feed penetration rule and truncated 2 relative angle of the rectangular receiver surface. The second part is the implementation of the antenna body and adoption of the antenna array method. We place each antenna body to rotate 90 degrees into the antenna array to achieve the purpose of a circular polarization array. The third part is the implementation of the satellite signal receiver, spectrum measurement, and analysis of the circular polarized microstrip array antenna design. In addition, performance comparison with large-scale helical antenna will be given. And as shown from our research, its efficiency and cost are both advantageous to large-scale helical antenna. In this thesis, we will present the following contributions: (1) Replacement：The thesis’ circular polarization microstrip array antenna design can be used as immediate replacement when experiencing failure for large helical antenna. This will avoid interruption in receiving task, resulting in data loss. (2) High Quality of Signal：Circular polarization microstrip array antenna makes use of array method to enhance the gain, improve directivity, and reach the narrow beam characteristic. At the same time, it reduces the level of interference signal influence, resulting to enhanced quality of signal reception of satellite communications. (3) Low-Cost-Effectiveness：This thesis’ circular polarization microstrip array antenna design doesn’t require a large amount of money to complete the antenna production. This not only meets low-cost-effectiveness, but also provides easy installation and removal. Finally, we can know that the circular polarization microstrip array antenna design presented in this thesis can effectively improve the antenna body gain, reduce the antenna cost and enhance the efficiency of signal reception. Accordingly, it increases the communications flexibility and other advantages.

碩士
正修科技大學
電子工程研究所
93
In this paper, We have presented about the compact CPW-fed square-ring-slot coupled microstrip antenna. We have investigated the characteristics of the proposed compact CPW-fed square-ring-slot coupled microstrip antenna. The properties of return losses, frequencies and radiation pattens have shown in this thesis. We have also discussed the effects on slot-ring and ground-plane size of the proposed antenna. The theoretical results have obtained from simulation software, HFSS. The software package HFSS is based on the differential equation and the Finite Element Methods. And, the experimental results have been verified by the HFSS simulation.

碩士
國立臺灣海洋大學
電機工程學系
106
This paper is on the design of sensing antenna for the detection of partial discharge inside the transformer tank. In this paper, from the perspective of system design by taking into consideration of the entire system set-up, a planar equiangular spiral antenna is proposed and placed in a variable-space transformer tank. The antenna cannot has grounding located in the insulating tank of the transformer tank. Therefore, a hemispherical radiation field antenna must be used to detect partial discharge in the transformer tank. In this thesis, the combined design of a circular and a ring microstrip antenna will be analyzed and discussed. The two microstrip antennas were integrated to form a hemispherical radiating field antenna. The resonant modes of the circular and ring microstrip antenna are analyzed and understood through theoretical calculation. From the theoretical analysis, the circular microstrip antenna is designed to radiate in the front direction while the ring microstrip antenna radiated along the sideways. The two types of antennas were then fabricated on a double-sided FR4 with an input impedance of 50 ohms. A power divider was also designed to integrate the two antennas. The combined system exhibited an insertion loss of -3 dB with good phase correlation. The return loss of the antenna system is measured to be -10 dB and radiated with the desired hemispherical radiation pattern at the intended frequency of 2.45 GHz. and the design frequency at 2.45 GHz.

碩士
大同大學
通訊工程研究所
99
In this thesis, a broadband circularly polarized antenna having two split rings fed by a micro strip line is presented. The proposed antenna can cover WLAN and WiMAX bands. The two rings are arranged side by side and are etched on the back-side of a printed circuit board. The open ends of the left and right split rings are positioned on the up-left and down-right directions. Experiments verify that the proposed antenna can produce a wide band circular polarization wave with 3dB axial ratio bandwidth of 46% (2.3GHz~3.7GHz). 10dB return loss bandwidth of the antenna is 45% (2.3GHz~3.7GHz) and the antenna gain is more than 1dBic within the overlapped return loss and axial ratio bandwidths. KEYWORD: micro strip antenna, circular polarization.

abstract: Global Positioning System (GPS) is a navigation system widely used in civilian and military application, but its accuracy is highly impacted with consequential fading, and possible loss of communication due to multipath propagation and high power interferences. This dissertation proposes alternatives to improve the performance of the GPS receivers to obtain a system that can be reliable in critical situations. The basic performance of the GPS receiver consists of receiving the signal with an antenna array, delaying the signal at each antenna element, weighting the delayed replicas, and finally, combining the weighted replicas to estimate the desired signal. Based on these, three modifications are proposed to improve the performance of the system. The first proposed modification is the use of the Least Mean Squares (LMS) algorithm with two variations to decrease the convergence time of the classic LMS while achieving good system stability. The results obtained by the proposed LMS demonstrate that the algorithm can achieve the same stability as the classic LMS using a small step size, and its convergence rate is better than the classic LMS using a large step size. The second proposed modification is to replace the uniform distribution of the time delays (or taps) by an exponential distribution that decreases the bit-error rate (BER) of the system without impacting the computational efficiency of the uniform taps. The results show that, for a BER of 0.001, the system can operate with a 1 to 2 dB lower signal-to-noise ratio (SNR) when an exponential distribution is used rather than a uniform distribution. Finally, the third modification is implemented in the design of the antenna array. In this case, the gain of each microstrip element is enhanced by embedding ferrite rings in the substrate, creating a hybrid substrate. The ferrite rings generates constructive interference between the incident and reflected fields; consequently, the gain of a single microstrip element is enhanced by up to 4 dB. When hybrid substrates are used in microstrip element arrays, a significant enhancement in angle range is achieved for a given reflection coefficient compared to using a conventional substrate.
Dissertation/Thesis
Ph.D. Electrical Engineering 2013

碩士
義守大學
電子工程學系碩士班
95
The CP (circularly polarization) antenna has been popular in the long distance communication due to its high noise-tolerant capability. Among many CP antennas, the semi-ring leaky-wave antenna with double-layers overcomes the shortcoming of traditional spiral antennas, and it can radiate broad-band CP electromagnetic wave only with a simple single-feeding. The advantages of the double-layer structure can easily match input impedance of antenna, and the CP band is adjustable based on demands. But the analysis on this antenna is not completed due to its complicated structure, and application is thus limited. Therefore, the purpose of this thesis is to establish the analysis theory for this CP antenna, as well as understand its concept and characteristics. First, this thesis introduces the CP concept by theoretical data. Later, the analysis of a single-layer semi-ring antenna is applied to double-layers ones. After appropriate process, the use of cavity model effectively obtains antenna characteristics, including propagation behavior, electrical distribution, radiation pattern and CP performance. The agreement between theory and simulation proves the validity of proposed method here. Besides, this thesis does not only summarizes the flow chart to design this kind of CP antenna, but analysis results also confirm that this antenna can operate in broad CP bands. Moreover, the high degree of freedom from structure enables the antenna to have different frequency bands for operation. By the modification of simulation, those results obtained by cavity model are close to reality, the accuracy of results eases the use of this antenna. This thesis establishes the fundamental theorem for double-layers semi-ring leaky-wave antennas, and the provided data and results are also useful for future applications.

碩士
義守大學
電子工程學系碩士班
97
This thesis applies PEC walls to reduce antenna size of a double-layer leaky-wave microstrip antenna with semi-ring structures which has the characteristics of broad-band operation and circular polarization (CP) radiation. From design point of view, proper antenna dimensions and operating frequency band are the key considerations to avoid unaccepted side-lobe radiation. After proper design, the results show that the size of this leaky-wave antenna is reduced sixty percent significantly, the characteristics of a general leaky-wave antenna still maintain. The inner radius at lower-layer and gap width variation of double-layer structure also increase design freedom, thus this antenna has adjustable broad-band CP and acceptable radiation pattern. As a result, CP bandwidth can be adjusted easily for different demands of application. The cavity model with modification is applied to analyze antenna performance, and the computer-aid simulations and semi-empirical method improve numerical accuracy, as well as verify design concept. And the step-by-step arrangement of investigation here and the adjustment of antenna dimensions are used to investigate antenna performances from all aspects; thus, the data in this thesis has become more reliable. The microstrip structure of this antenna itself owns the advantage to integrate with MMIC components as expected. If the technique of this size reduction can be applied to other complicated structure, the design concept is more valuable. The cavity model can be directly applied to structure with different substrate materials, provide that the cavity regions can be modified appropriately.