Dissertations / Theses on the topic 'Broadband microstrip antenna'

The use of the microstrip antenna has grown rapidly for the last two decades, because of the increasing demand for a low profile antenna with small size, low cost, and high performance over a large spectrum of frequencies. However, despite the advantages microstrip antennas provide, a number of technical challenges remain to be solved for microstrip antennas to reach their full potential, particularly if they are to be interfaced with monolithic circuits. The objective of this thesis is to examine novel methods for integrating and constructing broadband microstrip antennas, particularly at high microwave and millimeter wave frequencies where dimensions get very small and fabrication tolerances are critical. The first stage of the thesis investigates techniques to reduce the spurious feed radiation and surface wave generation from edge-fed patch antennas. A technique to reduce the spurious radiation from the edge-fed patch antenna by using a dielectric filled cavity behind the radiating element is explored. From this, a single element edge-fed cavity backed patch antenna was developed. Measured results showed low levels of cross polarization, making it suitable for dual or circular polarization applications. A 2 x 2 edge-fed cavity backed patch antenna array was also developed, which benefited greatly from this new technique due to the extensive feed network required. Furthermore, investigation into edge-fed cavity backed patches on high dielectric materials was also conducted. The measured impedance bandwidth of this edge-fed cavity backed patch is three times greater than the conventional edge-fed patch, and the gain increases to 5.1 dBi compared to 3.6 dBi. Further bandwidth enhancement of the single element edge-fed cavity backed antenna on high dielectric material was achieved by applying the hi-lo substrate structure. The hi-lo substrate structure produced an increase in the bandwidth to 26% from the 1.7% of the single element edge-fed cavity backed patch, while maintaining pattern integrity and radiation efficiency. Next, the development of a flip-chip bonding technique was investigated to enhance the fabrication accuracy and robustness of multilayer antennas on high dielectric materials. This technique was proven through simulation and experiment to provide good impedance and radiation performance via the high accuracy placement of the superstrate layer. The single element flip-chip patch antenna uses a high dielectric constant material for both the base and the patch superstrate, whereas the stacked flip-chip patch again uses a high and low permittivity material combination to achieve efficient wideband performance. Due to the high permittivity feed material, these antennas display the attributes required for integration with MMICs. The measured 10 dB return loss bandwidth of the single element was 4% with a gain of 4.6 dBi, whereas the stacked flip-chip patch showed very broadband performance, with a bandwidth of 23% with a gain of 8.5 dBi. The high accuracy placement and rigid attachment of the upper superstrat e layer via the flip-chip bonding technique also enables these antennas to be scaled up to millimeter-wave operational frequencies. The final section of this thesis is focused on developing a fabrication technique to enable the creation of a low permittivity layer at a nominated thickness.

Cylindrically conformal microstrip antennas are investigated. Two different structures, namely proximity coupled and E-shaped microstrip antennas are analyzed and information about the design parameters is obtained by means of parametric study. With these structures, cylindrical arrays, having omnidirectional radiation in the circumferential plane of the cylinder, are designed. Proximity coupled cylindrical arrays operate in the 2.3-2.4 GHz aeronautical telemetry band with approximately 4% bandwidth. On the other hand, more than 30% bandwidth is obtained by E-Shaped cylindrical array antenna structure, which also includes the commercial telemetry band. In order to verify the simulation method, a fabricated antenna in literature is simulated and acceptable agreement with simulation and fabrication results obtained.

Microstrip patch antennas are attractive for numerous military and commercial applications due to their advantages in terms of low-profile, broadside radiation, low-cost, low-weight and conformability. However, the inherent narrowband performance of patch antennas prohibits their use in systems that demand wideband radiation. To alleviate the issue, an existing approach is to combine multiple patch antennas within a log-periodic array configuration. These log-periodic patch antennas (LPMAs) are capable of providing large bandwidths (>50%) with stable broadside radiation patterns. However, they suffer from electrically large sizes. Therefore, their miniaturization without degrading the bandwidth performance holds promise for extending their use in applications that demand conformal and wideband installations. In recent years, electromagnetic band gap structures have been proposed to enhance the radiation performances of printed antennas. These engineered surfaces consist of a periodic arrangement of unit cells having specific metallization patterns. At particular frequencies, they provide a zero-degree phase shift for reflected plane waves and effectively act as high impedance surfaces. Since, their band-limited electromagnetic field behavior is quite similar to a hypothetical magnetic conductor; they are also referred to as artificial magnetic conductors (AMCs). AMC structures were shown to allow lower antenna profile, larger bandwidth, higher gain, and good unidirectional radiation by alleviating the field cancellation effects observed in ground plane backed antenna configurations. Previous research studies have already demonstrated that microstrip patch antennas can enjoy significant size reductions when placed above the AMC surfaces. This project, for the first time, investigates the application of AMCs to LPMA configurations. Specifically, the goal is to reduce the LPMA size while retaining its highly desired large bandwidth performance. To accomplish this, we employ various AMC surface configurations (e.g. uniform, log-periodic) under traditional LPMAs and investigate their performance in terms of miniaturization, bandwidth, gain, and radiation patterns.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The search for ever smaller device and without loss of performance has been increasingly investigated by researchers involving applied electromagnetics. Antennas using ceramics materials with a high dielectric constant, whether acting as a substract element of patch radiating or as the radiant element are in evidence in current research, that due to the numerous advantages offered, such as: low profile, ability to reduce the its dimensions when compared to other devices, high efficiency of ratiation, suitability the microwave range and/or millimeter wave, low temperature coefficient and low cost. The reason for this high efficiency is that the dielectric losses of ceramics are very low when compared to commercially materials sold used in printed circuit boards, such as fiberglass and phenolite. These characteristics make ceramic devices suitable for operation in the microwave band. Combining the design of patch antennas and/or dielectric resonator antenna (DRA) to certain materials and the method of synthesis of these powders in the manufacture of devices, it s possible choose a material with a dielectric constant appropriate for the design of an antenna with the desired size. The main aim of this work is the design of patch antennas and DRA antennas on synthesis of ceramic powders (synthesis by combustion and polymeric precursors - Pe- chini method) nanostructured with applications in the microwave band. The conventional method of mix oxides was also used to obtain nanometric powders for the preparation of tablets and dielectric resonators. The devices manufactured and studied on high dielectric constant materials make them good candidates to have their small size compared to other devices operating at the same frequency band. The structures analyzed are excited by three different techniques: i) microstrip line, ii) aperture coupling and iii) inductive coupling. The efficiency of these techniques have been investigated experimentally and compared with simulations by Ansoft HFSS, used in the accurate analysis of the electromagnetic behavior of antennas over the finite element method (FEM). In this thesis a literature study on the theory of microstrip antennas and DRA antenna is performed. The same study is performed about the materials and methods of synthesis of ceramic powders, which are used in the manufacture of tablets and dielectric cylinders that make up the devices investigated. The dielectric media which were used to support the analysis of the DRA and/or patch antennas are analyzed using accurate simulations using the finite difference time domain (FDTD) based on the relative electrical permittivity (er) and loss tangent of these means (tand). This work also presents a study on artificial neural networks, showing the network architecture used and their characteristics, as well as the training algorithms that were used in training and modeling some parameters associated with the devices investigated
A busca por dispositivos cada vez menores e sem perda de desempenho vem sendo cada dia mais investigada pelos pesquisadores da ?rea envolvendo eletromagnetismo apli- cado. Antenas utilizando materiais cer?micos com uma alta constante diel?trica, sejam elas atuando como substrato do elemento patch radiante ou como sendo o pr?prio ele- mento radiante est?o em evid?ncia nas pesquisas atuais, isso devido ?s in?meras vantagens que apresentam, tais como: baixo perfil, capacidade de redu??o de suas dimens?es (quando comparado a outros dispositivos), alta efici?ncia de radia??o, adequabilidade a faixa de micro-ondas e/ou ondas milim?tricas, baixo coeficiente de temperatura e baixo custo. A raz?o para essa alta efici?ncia ? que as perdas diel?tricas das cer?micas s?o muito baixas, quando comparadas ?s dos materiais comercialmente usados em placas de circuito impresso, tais como: fibra de vidro e fenolite. Essas caracter?sticas tornam os dispositivos cer?micos adequados para operar na faixa de micro-ondas. Aliando o projeto de antenas patch e/ou antenas ressoadoras diel?tricas (DRA) ao uso de certos materiais e ao m?todo de s?ntese desses p?s na fabrica??o dos dispositivos, ? poss?vel escolher um material com uma determinada constante diel?trica para o projeto de uma antena com o tamanho desejado. O objetivo principal deste trabalho consiste no projeto de antenas patches e antenas DRA sob s?ntese de p?s cer?micos (s?ntese por combust?o e por precursores polim?ricos - m?todo Pechini) nanoestruturados para aplica??es na faixa de micro-ondas. O m?todo convencional de mistura de ?xidos tamb?m foi utilizado na obten??o de p?s nanom?tricos para a confec??o das pastilhas e ressoadores diel?tricos. Os dispositivos fabricados e estudados sobre materiais de alta constante diel?trica os tornam bons candidatos ? fabrica??o de dispositivos e circuitos de dimens?es reduzidas quando comparado aos outros dispositivos tradicionais operando na mesma faixa de frequ?ncia. As estruturas analisadas s?o excitadas por tr?s diferentes t?cnicas: i) linha de microfita, ii) acoplamento por abertura e iii) acoplamento indutivo. A efici?ncia dessas t?cnicas de alimenta??o s?o investigadas experimentalmente e comparada com simula??es realizadas pelo Ansoft HFSS, utilizado na an?lise precisa do comportamento eletromagn?tico das antenas atrav?s do m?todo dos elementos finitos (FEM). Nesta tese um estudo bibliogr?fico sobre teoria de antenas de microfita e antenas DRA ? realizado. O mesmo estudo ? realizado a respeito dos materiais e dos m?todos de s?ntese dos p?s cer?micos que s?o utilizados na fabri- ca??o das pastilhas e dos cil?ndros diel?tricos que compor?o os dispositivos investigados. Os meios diel?tricos os quais serviram de suporte na an?lise das antenas patch e/ou DRA s?o analisados atrav?s de simula??es precisas utilizando o m?todo das diferen?as finitas no dom?nio do tempo (FDTD) com base na permissividade el?trica relativa (er) e tangente de perda desses meios (tand). Este trabalho ainda apresenta um estudo em redes neurais artificiais, evidenciando a arquitetura de rede utilizada e suas caracter?sticas, bem como os algoritmos de treinamento que foram usados no treinamento e na modelagem de alguns par?metros associados aos dispositivos investigados

Neste trabalho é realizada a otimização de antena de microfita banda larga usando o método de Diferenças Finitas no Domínio do Tempo (FDTD) e software comercial de onda completa. Inicialmente é feita uma introdução sobre o assunto, abordando aspectos de comunicações e de antenas de microfita, além de se fazer uma revisão bibliográfica e resumir o estado da arte sobre o tema do trabalho. A seguir, discorre-se sobre a teoria eletromagnética aplicada a antenas planares. O tópico de base é concluído com síntese dos métodos de simulação usados na análise de antenas de microfita, enfatizando o de FDTD. O próximo item revisa fundamentos teóricos e técnicas aplicadas na obtenção de banda larga em antenas de microfita. O trabalho prossegue com simulações numéricas e medidas da largura de banda, do ganho e da eficiência da antena E e de geometria inovadora aplicando técnica de alimentação capacitiva à antena E. A seguir, o algoritmo genético é apresentado e utilizado na otimização do plano de terra de antena de microfita com alimentação por sonda coaxial e também com alimentação capacitiva, para aplicações em banda larga. Resultados simulados e medidos são apresentados e boa concordância entre eles é obtida. Obteve-se 88% de largura de banda para PIFA com alimentação capacitiva e plano de terra otimizado. A tese é concluída com observações sobre os resultados apresentados e sugestões para prosseguimento e aperfeiçoamento das investigações realizadas.
In the present work, the optimization of broadband microstrip antenna employing the Finite Difference Time Domain (FDTD) and full wave commercial software are presented. First, an introduction on the subject considering main issues in communications and microstrip antennas are described, also a bibliographical review and the state of the art are presented. A review of electromagnetic theory applied to microstrip antenna is presented at the following topic, with emphasis on the FDTD method. The next step is a review of theory and techniques on bandwidth optimization of microstrip antennas. The work follows with numeric simulations and measurements on bandwidth, gain, efficiency of E shapped antenna and with a novel design procedure employing capacitive feeding on the E shapped antenna. The work follows with genetic algorithm being presented and utilized to the optimization of ground plane shape microstrip antenna with coaxial feeding and also with capacitive feeding, aiming to broadband applications. Simulated and measured results are presented. Good agreement is observed. Relative bandwidth of 88% was found for PIFA with capacitive feeding and optimized ground plane. The thesis is concluded with some comments and observations on the results obtained and suggestions for the continuation of the work.

This diploma thesis deal with the design of log-periodic antenna. The log-periodic antenna is self-complementary and broadband antenna. Antenna self-complementary structures are described only by angles. Input impedance of log-periodic antenna is equal to theoretical impedance ohms. The input impedance and radiation patterns of broadband antenna structures are independent of frequency over theoretically unlimited bandwidths. The log-periodic antennas provide linearly polarized radiation pattern. In this thesis is designed antenna for bandwidths 1 to 5GHz. In this diploma thesis is introduced design balanced unit, this is compound broadband balun and broadband impedance transformer. The broadband balun is based on conversion of microstrip line to balanced stripline. The Klopfenstein impedance taper is used for design. For simulation was used software from firma Zeland software IE3D.

The purpose of this thesis is to investigate a novel method to develop broadband microstrip (patch) antennas using substrates containing photonic crystals. Photonic crystals are a class of periodic dielectric, metallic, or composite structures that when introduced to an electromagnetic signal can exhibit a forbidden band of frequencies (or bandgap) in which the incident signal destructively interferes and thus is unable to propagate. It is proposed that such photonic crystals will reduce surface waves and prohibit the formation of substrate modes, which are commonly known inhibitors of patch antenna designs. By reducing or eliminating the effects of these electromagnetic inhibitors with photonic crystals, a broadband response can be obtained from inherently narrowband antennas. In addition, it is also proposed that the behavior of the photonic crystals will lead to a reduction in pattern sidelobes resulting in improvements in radiation pattern front-to-back ratio and overall antenna efficiency. This research is verified through analytical simulations and experimental investigations in the Virginia Tech anaechoic chamber.
Master of Science

The ever increasing diversity in communication systems has created a demand for constant improvements in receiver components. This thesis describes the design and characterisation of front-end receiver components for various challenging applications, including characterisation of low noise foundry processes, LNA design and multi-band antenna design. It also includes a new theoretical analysis of noise coupling in low noise phased array receivers.In LNA design much depends on the choice of the optimum active devices. A comprehensive survey of the performance of low noise transistors is therefore extremely beneficial. To this end a comparison of the DC, small-signal and noise behaviours of 10 state-of-the-art GaAs and InP based pHEMT and mHEMT low noise processes has been carried out. Their suitability in LNA designs has been determined, with emphasis on the SKA project. This work is part of the first known detailed investigation of this kind. Results indicate the superiority of mature GaAs-based pHEMT processes, and highlight problems associated with the studied mHEMT processes. Two of the more promising processes have then been used to design C-band and UHF-band MMIC LNAs. A new theoretical analysis of coupled noise between antenna elements of a low noise phased array receiver has been carried out. Results of the noise wave analysis, based on fundamental principles of noisy networks, suggest that the coupled noise contribution to system noise temperatures should be smaller than had previously been suggested for systems like the SKA. The principles are applicable to any phased array receiver. Finally, a multi-band antenna has been designed and fabricated for a severe operating environment, covering the three extremely crowded frequency bands, the 2.1 GHz UMTS, the 2.4 GHz ISM and the 5.8 GHz ISM bands. Measurements have demonstrated excellent performance, exceeding that of equivalent commercial antennas aimed at similar applications.

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This work presents techniques used to design and manufacture microstrip patch antennas for applications in portable and mobile devices. To do so, are evaluated several factors that can influence the performance of microstrip patch antennas. Miniaturization techniques are studied and employed in order to apply this type of antenna in mobile and / or mobile. The theories of microstrip patch antennas are addressed by analyzing characteristics such as constitution, kinds of patches, substrates, feeding methods, analysis methods, the main advantages and disadvantages and others. Techniques for obtaining broadband microstrip patch antennas were surveyed in literature and exemplified mainly by means of simulations and measurements. For simulations of the antennas was used the commercial software . In addition, antenna miniaturization techniques have been studied as a main concern the fundamental limits of antennas with special attention to electrically small antennas because they are directly linked to the microstrip patch antennas. Five design antennas are proposed to demonstrate the effectiveness of techniques used to obtain the microstrip patch antennas broadband and miniaturized for use in mobile devices and/or portable. For this, the proposed antennas were simulated, built and measured. The antennas are proposed to be used in modern systems of wireless communications such as DTV, GPS, IEEE 802.16, IEEE 802.11, etc. The simulations of the antennas were made in business and computer programs. The measured results were obtained with a parser Vector of networks of the Rhode and Schwarz model ZVB 14
Esse trabalho apresenta t?cnicas usadas para projetar e fabricar antenas patch de microfita para aplica??es em dispositivos port?teis e m?veis. Para isso, s?o avaliados diversos fatores que podem influenciar no desempenho das antenas patch de microfita. T?cnicas de miniaturiza??o s?o estudadas e empregadas visando a aplica??o deste tipo de antena em dispositivos port?teis e/ou m?veis. Fundamentos te?ricos sobre as antenas patch de microfita s?o abordados analisandose caracter?sticas como: constitui??o, tipos de patches, substratos, m?todos de alimenta??o, m?todos de an?lises, principais vantagens e desvantagens dentre outros. T?cnicas para obten??o de antenas patch de microfita banda larga foram pesquisadas na literatura e exemplificadas principalmente por meio de simula??es e medi??es. Para as simula??es das antenas foi utilizado o programa computacional comercial . Al?m disso, t?cnicas de miniaturiza??o de antenas foram estudadas tendo como preocupa??o principal os limites fundamentais das antenas com aten??o especial a antenas eletricamente pequenas por estarem diretamente vinculadas ?s antenas patch de microfita. Cinco projetos de antenas s?o propostos para comprovar a efici?ncia das t?cnicas utilizadas para obten??o de antenas patch de microfita banda larga e miniaturizadas, para aplica??o em dispositivos m?veis e/ou port?teis. Para isso, as antenas propostas foram simuladas, constru?das e medidas. As antenas foram propostas para serem utilizadas em sistemas modernos de comunica??es sem fio como: DTV, GPS, IEEE 802.16, IEEE 802.11, etc. As simula??es das antenas foram feitas nos programas computacionais comerciais e . Os resultados medidos foram obtidos com um analisador vetorial de redes da Rhode and Schwarz modelo ZVB 14

As the interest in intentional electromagnetic interference (IEMI) increases, so does the need of a suitable antenna which endures those demanding conditions. The ultrawideband (UWB) technology provides an elegant way of generating high-voltage UWB pulses which can be used for IEMI. One UWB antenna, invented solely for the purpose of radiating pulses, is the impulse radiating antenna (IRA). In the course of this master thesis work, a suitable geometry of the IRA is suggested, and modelled, for the high-voltage application of 90 kV.

碩士
義守大學
電子工程學系
89
Broadband and circular polarization(cp) is essential in many microwave application .The reason why we note is that it gets the ability of increasing the transmission speed and reducing the multipath reflection and several kind of interference. So the microstrip patch antennas that own the advantages are widely utility in Communication .In this article ,we propose a new simple design to conquer the narrow impedance and polarization bandwidth that is produced by single patch , single feed on the same layer. Moreover, we construct the double-layer structure, upper is circular radiating patch and lower is wilkinson power divider.The power divider has a 90。shift difference(1/4λlength difference) between its two outputs. But the bandwidth is limitted by the inductance introduced by the long conductor feeds . In this new design ,we load branch capacitance on power divider 70.7Ω branch parallelly the isolation resistance 100Ωto cancel out the inductance. By controlling the branch-capacitance and the height of air layer ,the 49% impedance bandwidth and 20% cp bandwidth are obtained.

碩士
國立彰化師範大學
電信工程研究所
96
Abstract In this thesis, we propose a broadband circularly polarized shorted wall antenna, which design procedure of broadband circularly polarized fed by an L-probe. For the broadband circularly polarized antenna design, the antenna dimension is made suited for operating in 1.80 GHz band. The distance between patch antenna and ground plan is 0.96λ0. Use a horizontal rectangular metal strip and a vertical cylinder copper to form L-probe feed. The impedance of the antenna can be controlled by tuning the length and width of the rectangular metal strip. This shorted wall antenna has two shorting to form vertical field and can obtain the circularly polarized radiation characteristic. Achieving the 3-dB axial ratio bandwidth of 44.4% and the 10-dB impedance bandwidth of 50%. The shorted wall is designed using CST STUDIO SUITE 2006 microwave electromagnetic simulation software.

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
國立臺南大學
通訊工程研究所碩士班
98
Because of the developing of modern wireless communication, the requirement of antenna operation bandwidth is not only narrow-band or dual-band, but wideband antenna. There are so many wireless communications could be used, and new systems and channels are proposed in international market. The designers of antenna will consider many communication systems, like GSM, WLAN and GPS etc... In this thesis, we proposed a wideband circularly polarized microstrip antenna. The proposed antenna has circularly polarization in specific frequency. For reducing the volume of the proposed antenna, we designed the passive components with microstrip transmission line. We also simplify the complex of antenna structure by feeding into antenna using microstrip line. We are using the Wilkinson power divider provides equal power division and the Schiffman phase shifter provides to satisfy the conditions of circularly polarization. The phase deviation of the feeding signal is controlled by adjusting the Z0e and Z0o of the Schiffman phase shifter. Finally, we cascaded the Wilkinson power divider and the Schiffman phase shifter to feed into two mono-polarized antennas. The proposed antenna has a wide operation bandwidth and satisfying circularly polarization performance in specific frequency. The operation bandwidth of the proposed antenna is 114% (from 0.7 to 2.57 GHz); and the axis ratio bandwidth is 26% (from 1.22 to 1.59 GHz). The radiation patterns are ommi-directional at each operation frequency.

This thesis provides several designs of broadband microstrip antennas for the use in WLAN applications. It also highlights the novel reconfigurable microstrip antenna design. The main objective of this thesis is to design a novel microstrip antenna that is broadband, circularly polarized, multiband, reconfigurable and easy-to-fabricate. The thesis, in the first stage, presents a review of various different options available when designing and manufacturing wideband microstrip antennas. The review includes basic theory of microstrip patch antennas, matching techniques and broadbanding techniques. The second stage concentrates on the development of a couple of working prototype antenna designs and finally presents the design of a reconfigurable antenna that can perform over several frequency bands. The shapes of broadband patch antennas used are rectangular, circular and triangular. The multiple resonance technique is used in the design of the broadband antennas. Numerical and measured results are presented and discussed. The proposed patch antennas give measured bandwidth up to 28.5%. The reconfigurable antenna on the other hand is designed to possess frequency and polarization reconfigurability, and can operate in six different frequency bands. In addition to the bandwidth advantage, the proposed configuration offers easy reconfigurability with the ability to exclude switches in the combination part of the feed network. The important aspect of this design is that it provides a high size reduction for all the operating frequencies compared to conventional rectangular patches. Besides compactness all proposed antennas have gain better than 7dB. The proposed antennas are found to be suitable for WLAN standards.

碩士
大葉大學
電機工程學系
106
Abstract—In this paper, we study a circularly polarized microstrip antenna on a suspended substrate with a coplanar capacitive feed and a slot within the rectangular patch. Although microstrip antenna has been widely used in linear polarization, circular polarization (CP) operation may be obtained by modifying the structure of the basic antenna and/or feed. Modifications include adjusting the size of antenna and cutting a slot inside the rectangular patch,and research the uspended substrate, and this structure can be scaled to any frequency that you want to use. The axial ratio bandwidth of the antenna is 5.25GHz~5.5GHz (<3dB). The antenna has an impedance bandwidth of 4.5 GHz to 5.75 GHz ( <−10 dB), And in the useful range of circular polarization also yields return loss better than -30dB. Measured characteristics of the antenna characteristics are in good agreement with the simulation results.

碩士
國立交通大學
電信工程研究所
103
In this thesis, we used the broadband tapered half-width microstrip leaky-wave antenna as the unit element to design a four-element antenna array. The half-width structure is used to simplify the conventional feeding structure. In the half-width structure, the perfect electric conductor (PEC) wall is realized by via holes connecting the two metallic layers on substrate. The advantages of this structure are : (I) simple feeding structure fed by microstrip line; (II) pure mode excitation and no need to suppress mode; (III) reduced size as compared to the full-width structure; and (IV) less coupling between array element. Based on the characteristics of the first higher order leaky-mode for the microstrip antenna, this thesis proposed a scheme for the empirical design of broadband tapered half-width microstrip leaky-wave antenna array. The measured bandwidth of the antenna has a return loss less than -10 dB from 14 GHz to 30 GHz, yielding a relative bandwidth of 2.3 : 1. In this thesis, we also proposed a novel design scheme for the empirical design of broadband tapered half-width microstrip leaky-wave antenna array to improve the radiation patterns in higher frequency. The measured bandwidth of the antenna has a return loss less than -10 dB from 14 GHz to 30 GHz(relative bandwidth of 2.3 : 1), and the main beam bifurcation in the previous design was alleviated.

碩士
國立彰化師範大學
電信工程研究所
98
This paper proposes a new design for a circularly polarized microstrip antenna and analyzes its characteristics. Using the advantages of a shorting wall antenna, such as simple structure, small volume, and low cost, this paper designs a broadband, partially shorted, microstrip antenna with circular polarization. Software simulations reveal its characteristics. Two mechanisms in the antenna structure were able to excite the circularly polarized mode, and the antenna dimension was designed to operate in the 1.80 GHz band. Furthermore, to achieve the broadband effect, this study proposes the use of an L-probe feed to excite the antenna. This L-probe feed consists of a rectangular metal strip and a copper cylinder. The air dielectric served as a substrate, and the copper cylinder produced inductance as the structure height increased. Adjusting the length of the rectangular metal strip effectively alleviated the parasitic inductance effect of the copper cylinder. This design made it possible to control the impedance matching of the antenna and achieve broadband effects. The impedance bandwidth ranged from 1.62 GHz to 2.47 GHz (10 dB impedance bandwidth of about 41.6 %), and the circularly polarized bandwidth ranged from 1.55 GHz to 2.07 GHz (3 dB axial ratio bandwidth of about 28.73 %), showing the feasibility of the proposed microstrip antenna.

碩士
國立交通大學
電信工程系所
95
Generally, leaky wave antennas have the advantages: high gain, high radiation efficiency, low cost. In this thesis, we study the first higher order mode broadband microstrip leaky-wave antennas. We will implement the first higher order mode leaky wave antenna by the broadband balun. The inverted balanced microstip line structure is developed from the balanced microstrip line. The position of the positive strip on the upper substrate side is exchanged with that of the negative strip on the lower substrate side by the method proposed in this thesis.United with the balanced microstrip line, this inverted balanced microstrip line can be used to form into a pair of broadband baluns. Using this broadband balun can realize a broadband leaky-wave antenna. Based on the characteristics of the first higher order leaky-mode for the microstrip antenna, this thesis proposes a scheme for the empirical design of broadband tapered microstrip leaky-wave antenna. The measured bandwidth of the tapered microstrip leaky-wave antenna has a from 10GHz to 40GHz, yielding a relative bandwidth of 4:1. Finally, this thesis proposes a novel scheme for the empirical design of lower sidelobe broadband tapered microstrip leaky-wave antenna.

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.

碩士
大葉大學
電機工程學系
107
This paper make use of C-Band in Circularly polarized antennas research that use HFSS software. This antenna composed of rectangle slot ground plane and microstrip line. Focus on design of Asymmetry feed and ground plane, make the ground plane and antenna emerge right angle phase difference of orthogonality, Circularly polarized is generated. Analysis result of antenna apply to C-Band that reflection Roefficient coverage (3.7~10)GHz and Axial ratio coverage (4.6~6.9)GHz.

Recent days, antennas play an important role in wireless communication system. Microstrip patch antennas are well known to have positive features for cost-effective, low profile and broadband. This type of antenna can be used in wide range of applications such as in wireless communications, radar systems, and satellites. Inhibiting characteristics of single patch antenna with low gain and narrow band leads to the research area to have array configuration. Beam steering antennas are the ideal solution for various systems such as traffic control and collision avoidance radar systems. The goal of this work is to design and implement a dual-linear polarization stacked microstrip patch phased array antenna. Single stacked microstrip patch antenna fed by microstrip line was designed to have approximately 3 GHz bandwidth in X-band with another ground plane to form a stripline-fed. Stripline-fed design protects feed lines from any outside effects. The array configuration was adapted to design in order to accomplish beam scan angle of /- 30 degrees by /- 15 degrees. Binomial power distribution of 3x2 array structure was used in order to reduce grating lobes, and changing length of feed lines was implemented for phase shifting. Bowtie cross shape aperture and dual-offset microstrip feedline was used to feed radiating patches. For the feed network, T-split power divider was implemented and optimized to achieve low loss. The length of microstrip line was adjusted to meet desired phase shift that in wideband application, the length of the line had to be long enough to have similar wavelength response over broad frequency range. The antenna array was designed using standard equations and simulated by electromagnetic analysis software called Zealand's IE3D which is method-of-moments based simulator. The resulting measured impedance bandwidth and gain of both microstrip and stripline-fed single antenna are 43 percent and 5 to 10 dBi with low cross polarizations for all frequencies. The array antenna was measured to have 29 to 60 percent impedance bandwidths depending on the different types of beam scan angles. The gain of the array antenna is 8 to 13 dBi, and the beams are directed as required with /- 3 degrees beam scan angle tolerance. The array antenna had a small offset as compared with simulated results because of the fabrication process such as alignment, distorted feed lines while etching, and etc, but the bandwidths and array patterns were acceptable.

碩士
國立交通大學
電信工程研究所
103
In this thesis, we use the broadband tapered half-width microstrip leaky-wave antenna to be the unit element and design an eight element antenna array. We use the half-width structure to simplify the conventional feeding structure, which is 180°out of phase. In the half-width structure, the PEC wall is constructed by via holes conducting the two metallic layers on substrate. The advantages of this structure are: (I) simple feeding structure fed by microstrip line ; (II) pure mode excitation and no need to suppress mode ; (III) reduced size as compared to the full-width structure ; (IV) less interaction in an array design. Based on the characteristics of the first higher order leaky-mode for the microstrip antenna, this thesis proposes a scheme for the empirical design of half-width microstrip leaky-wave antenna arrays . The measured bandwidth of the antenna has a return loss less than -10 dB from 6.5 GHz to 30 GHz, yielding a relative band width of 4.29 : 1. In this thesis, we also propose a novel coupled-mode scheme for the empirical design of half-width microstrip leaky-wave antenna arrays with varying periodic vias to control the propagation characteristics optimization of bandwidth. Based on the measurement results, we realize a bandwidth of 2 GHz in previously antenna array.

博士
國立中山大學
電機工程學系研究所
89
Novel broadband designs of microstrip antennas have been proposed in this dissertation, including bandwidth enhancement using integrated reactive loading, broadband circularly polarized designs, broadband dual-frequency design, bandwidth enhancement using a slotted ground plane and practical applications. First, bandwidth enhancement of microstrip antennas using integrated reactive loading is proposed and experimentally studied. Results show that the proposed antennas can have an operating bandwidth more than 2.0 times that of a conventional one at a given operating frequency. Second, by selecting a thick air substrate, a wideband circularly polarized microstrip antenna with improved CP quality has been implemented. In addition to the improved CP quality obtained, a 2-dB axial-ratio bandwidth as large as about 38% is also achieved. Third, by bending a planar rectangular patch into an inverted L-shaped patch, a dual-frequency planar antenna has been obtained. Experimental results show that the proposed antenna has a tunable frequency ratio of about 1.66-2.29. Fourth, by embedding meandering slots or slits in the antenna’s ground plane, it is observed that the impedance bandwidth of the microstrip antenna is twice larger than the conventional one. The experimental results show that the resonant frequency is significantly lower, which can lead to a large antenna size reduction for a fixed frequency operation. In addition, enhanced antenna gain is also obtained. Finally, a shorted patch antenna suitable for applications in DCS (1710-1880 MHz) base station is presented.

碩士
明新科技大學
電機工程研究所
96
In this thesis we study microstrip antennas fed by coplanar waveguides (CPW). A CPW-fed microstrip antenna is a simple structure and easy to be fabricated and incorporated in microwave integrated circuits (MIC). There are two types of microstrip antennas, wide slotted microstrip antennas and planar inverted F antennas (PIFA), studied in this thesis. Based on wideband characteristic of a wide slotted antenna in the first antenna we suggest that using a radial tuning stub combined with a 50 ohm CPW line as a feed of a wide slotted antenna to increase antenna bandwidth. Under a fixed slot size of antenna we change the radial angleθof the tuning stub to get a wider bandwidth. The input impedance bandwidth, radiation pattern, and gain of the antenna are also studied during this work. The second antenna is a PIFA. A PIFA is simply a monopole antenna. With a ground stub PIFA has a higher frequency resonant loop to generate higher frequency loop mode with respect to lower frequency monopole mode. Therefore, PIFA can be designed as a dual-band antenna. Considering the feed and multi-frequency bands the PIFA is designed to fit into wireless local area network (WLAN) system, especially to meet the IEEE802.11 a/b/g dual-band requirement. The analysis and design of two antennas are simulated by using simulation software, IE3D and HFSS. The antennas are fabricated on single metal layered printed circuit boards (PCB). The impedance of antennas is measured by using network analyzers. The radiation patterns and gain are measured in an anechoic chamber.

碩士
國立交通大學
電信工程研究所
104
In this thesis, we use half-width structure instead of conventional full-width structure which has the complex feeding structure to design leaky-wave antenna. In the half-width structure, we take the periodic via holes connecting between top and bottom metallic layers as the PEC wall. So, we can figure out the advantages of the half-width structure are shown below: (I) simple feeding structure just using microstrip line (II) pure the first-higher-order leaky-mode excitation and no need to suppress EH0 mode (III) reduced antenna size compared to the full-width structure . Based on the characteristics of the first higher leaky-mode for the microstrip antenna, this thesis proposes a design flow of broadband tapered half-width microstrip leaky-wave antenna by numerical analysis and simulation software. The simulated bandwidth of the antenna is from 7 GHz to 13 GHz and the angle of main beam is not changed with the varied frequency in operation bandwidth. On the other hand, we also propose a design flow that use varied periodic via holes to control propagation characteristics to make the pattern of proposed antenna impoved. The simulated bandwidth of the antenna is from 9 GHz to 12.5 GHz and the peak side lobe level is reduced 4 dB.

碩士
國立臺灣大學
電信工程學研究所
99
A concept for designing a broadband aperture-coupled microstrip patch antenna is presented in this thesis. The proposed patch antenna is fed by a coupling aperture, offset from the patch center. This generates a fictitious open circuit within the resonating edges of the patch, and therefore, an additional resonant frequency is produced and a wide impedance bandwidth can be obtained. Also, a broadband patch array using the patch as its radiating elements is presented. All the designs are fabricated and verified via both measurements and simulations. Then, the proposed patch array is integrated with an off-the-shelf power amplifier module, and the power density radiated by the system is further characterized. Finally, this system is used as a microwave virus sanitizer to eliminate the H1N1 viruses, and a series of experiments is setup and performed. The associated results are also presented.