ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / This paper will discuss the design of a new antenna element for use on vehicles requiring a thin conformal antenna such as on missiles or targets. The new element employs a partial shorted edge, which reduces the size of the element compared to a traditional microwave patch, while maintaining the impedance bandwidth.

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Approved for public release; distribution is unlimited / This thesis addresses the prototyping, measurement, and validation of two circularly polarized microstrip patch antennas designed by LTJG Mahmut Erel for the NPSAT-1. The antenna system (receive and transmit), consisting of two antennas on a ground plane and their feed systems, was field-tested. The results were compared to the CSTʼ Microwave Studio. Finite Difference Time Domain (FDTD) software package predictions in order to verify that this design satisfies the NPSAT-1 requirements for bandwidth, free-space radiation pattern and low-profile shape. / Lieutenant Junior Grade, Turkish Navy

by Wai-Chung Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 121-124). / Abstract also in Chinese. / Acknowledgement --- p.i / Abstract --- p.ii / Table of contents / Chapter Chapter 1: --- Introduction --- p.1 / Chapter Chapter 2: --- Background Theories --- p.4 / Chapter 2.1 --- Introduction --- p.4 / Chapter 2.2 --- Maxwell's Equations --- p.5 / Chapter 2.3 --- Basic Formulation --- p.8 / Chapter 2.4 --- Plane Wave Formulation --- p.13 / Chapter 2.4.1 --- Total-Field / Scattered-Field Algorithm --- p.14 / Chapter 2.4.2 --- Pure Scattered-Field Algorithm --- p.16 / Chapter 2.4.2.1 --- Application to PEC Structures --- p.16 / Chapter 2.4.2.2 --- Application to Lossy Dielectric Structures --- p.17 / Chapter 2.5 --- Incident Plane Wave Components Generation --- p.20 / Chapter 2.6 --- Source and Termination Modeling in FD-TD model --- p.24 / Chapter 2.6.1 --- Resistive source --- p.25 / Chapter 2.6.2 --- Resistor Formulation --- p.27 / Chapter 2.7 --- PML Formulation --- p.28 / Chapter 2.7.1 --- Two-Dimensional TE Case --- p.28 / Chapter 2.7.2 --- Extension to the Full-vector Three-Dimension Case --- p.32 / Chapter 2.8 --- Time Domain Extrapolation --- p.33 / Chapter 2.8.1 --- Prony's Model --- p.34 / Chapter 2.8.2 --- Auto-regressive Model and Performance Comparison with Prony's Method --- p.36 / Chapter 2.9 --- Summary --- p.42 / Chapter Chapter 3: --- Verification of FD-TD Method --- p.43 / Chapter 3.1 --- Introduction --- p.43 / Chapter 3.2 --- Microstrip Patch Antenna: An Introduction --- p.44 / Chapter 3.2.1 --- Direct Fed Patch --- p.45 / Chapter 3.2.2 --- EMC Patch --- p.50 / Chapter 3.2.3 --- Aperture-Coupled Patch --- p.53 / Chapter 3.3 --- Verification of FD-TD: S11 Analysis --- p.55 / Chapter 3.3.1 --- Analysis of Direct Fed Rectangular Patch Antenna --- p.56 / Chapter 3.3.2 --- Analysis of EMC Patch Antenna --- p.60 / Chapter 3.3.3 --- Analysis of Aperture-Coupled Patch Antenna --- p.63 / Chapter 3.4 --- Verification of FD-TD: Radiation Pattern Analysis --- p.66 / Chapter 3.4.1 --- The Absolute and Relative Approaches --- p.67 / Chapter 3.4.2 --- The Inset Fed Patch Antenna --- p.69 / Chapter 3.5 --- Summary --- p.71 / Chapter Chapter 4: --- Space Diversity Design --- p.73 / Chapter 4.1 --- Introduction --- p.73 / Chapter 4.2 --- How Space Diversity Antenna Works --- p.74 / Chapter 4.3 --- Criteria for Evaluation and Optimization of Diversity Performance --- p.77 / Chapter 4.4 --- Simple Approach for Two-Patch Diversity Array --- p.82 / Chapter 4.4.1 --- Performance as a Function of Antenna Separation --- p.83 / Chapter 4.5 --- Novel Designs for Performance Improvement --- p.89 / Chapter 4.5.1 --- Shorting Post Isolation --- p.90 / Chapter 4.5.2 --- Offset-positioned Configuration --- p.101 / Chapter 4.6 --- Three-Patch Diversity Array --- p.106 / Chapter 4.6.1 --- Co-aligned Configurations --- p.107 / Chapter 4.6.2 --- Offset-Positioned Configurations --- p.112 / Chapter 4.7 --- Summary --- p.117 / Chapter Chapter 5: --- Conclusion --- p.118 / Appendix A: Publication --- p.121 / Appendix B: References List --- p.122

Mutual Coupling (MC) is the exchange of energy between multiple antennas when placed on the same PCB, it being one of the critical parameters and a significant issue to be considered when designing MIMO antennas. It appears significantly where multiple antennas are placed very close to each other, with a high coupling affecting the performance of the array, in terms radiation patterns, the reflection coefficient, and influencing the input impedance. Moreover; it degrades the designed efficiency and gain since part of the power that could have been radiated becomes absorbed by other adjacent antennas' elements. The coupling mechanism between multiple antenna elements is identified as being mainly through three different paths or channels: surface wave propagation, space (direct) radiation and reactive near-field coupling. In this thesis, various coupling reduction approaches that are commonly employed in the literature are categorised based on these mechanisms. Furthermore, a new comparative study involving four different array types (PIFA, patch, monopole, and slot), is explained in detail. This thesis primarily focuses on three interconnected research topics for mutual coupling reduction based on new isolation approaches for different wireless applications (i.e. Narrowband, Ultra-wide-band and Multi-band). First, a new Fractal based Electromagnetic Band Gap (FEBG) decoupling structure between PIFAs is proposed and investigated for a narrowband application. Excellent isolation of more than 27 dB (Z-X plane) and 40 dB (Z-Y plane) is obtained without much degradation of the radiation characteristics. It is found that the fractal structures can provide a band-stop effect, because of their self-similarity features for a particular frequency band. Second, new UWB-MIMO antennas are presented with high isolation characteristics. Wideband isolation (≥ 31 dB) is achieved through the entire UWB band (3.1-10.6 GHz) by etching a novel compact planar decoupling structure inserted between these multiple UWB antennas. Finally, new planar MIMO antennas are presented for multi-band (quad bands) applications. A significant isolation improvement over the reference (≥ 17 dB) is achieved in each band by etching a hybrid solution. All the designs reported in this thesis have been fabricated and measured, with the simulated and measured results agreeing well in most cases.

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.

<p><p>Microstrip structures became very attractive with the development of cost-effective dielectric materials. Among several techniques suitable to the analysis of such structures, the discrete mode matching method (DMM) is a full-wave approach that allows a fast solution to Helmholz equation. Combined with a full-wave equivalent circuit, the DMM allows fast and accurate analysis of microstrips lines on multilayered substrates.</p><p> </p><p>The knowledge of properties like dispersion and electromagnetic fields is essential in the implementation of such transmission lines. For this objective a MATLAB computer code was developed based on the discrete mode matching method (DMM) to perform this analysis.</p><p> </p><p>The principal parameter for the analysis is the utilization of different dielectric profiles with the aim of a reduction in the dispersion in comparison with one-layer cylindrical microstrip line, showing a reduction of almost 50%. The analysis also includes current density distribution and electromagnetic fields representation. Finally, the data is compared with Ansoft HFSS to validate the results.</p></p> / The German Aerospace Center has rights over the thesis work

<p>The demand of small size electronic systems has been increasing for several decades. The physical size of systems is reduced due to advancements in integrated circuits. With reduction in size of electronic systems, there is also an increasing demand of small and low cost antennas. Patch antennas are one of the most attractive antennas for integrated RF front end systems due to their compatibility with microwave integrated circuits. To fulfil the demand of integrated RF front end systems, a design of microstrip patch antenna with optimum performance at 70GHz is investigated. The procedure could be extended to design other planar antennas that act in a similar way.</p><p>In this work, three different design methods to design patch antennas for applications at 70GHz are investigated that include use of analytical models, numerical optimization, and numerical variation of dimensions. Analytical models provide a basic understanding of the operation of a patch antenna and they also provide approximate dimensions of a patch antenna for a targeted frequency without using numerical simulations. However, as the operating frequencies of RF systems reach mm-wave frequencies, we expect that the accuracy of analytical models become less accurate. For example, the excitation of substrate modes and effect of ground size are not predicted in simple analytical models.</p><p>Due to these expected limitations of the analytical design methods, the accuracy of these models is investigated by numerical electromagnetic field simulations. In this work, CST Microwave Studio Transient Solver is used for that purpose. In order to make sure that the appropriate settings of the solver are applied, the simulation settings such as mesh density, boundary conditions and the port dimensions are investigated. The simulation settings may affect computation time and convergence of the results. Here, in this work, the accuracy of the simulator for a specific design of inset feed rectangular patch antenna is verified. The patch dimensions obtained from analytical calculations are optimized at 70GHz by using the optimizer of the transient solver. The patch dimensions obtained from optimizer are verified by varying the patch dimensions in equidistant steps around the found result of the optimizer.</p><p>In a rectangular microstrip patch antenna design, the use of a width of 1.5 times the length is an approximate rule of thumb [1] for low dielectric constant substrates. It is also investigated how the performance properties of a microstrip patch antenna are affected by varying the width to length ratio of the patch. There are occasions where a different ratio is required because of space limitations, or to change the input impedance. The patch designs having various width to length ratios were optimized with the feed location.</p><p>The analytically calculated dimensions provided good initial values of the rectangular patch antenna for further optimization using more accurate techniques. The design have been optimized at 70GHz for the investigated mesh density, boundary conditions and the port dimensions. The numerical variation of dimensions is found to be most reliable among the investigated design methods but it is more complicated with many parameters.</p>

Modern wireless communication systems call for ultra wideband operations to meet the continuous growth in the number of users of these systems. Since antenna is an integral part of any wireless communication system (transmitter or receiver), designing antennas with good gain over large bandwidth needs to be considered first. To meet the popular demand, wireless communication systems should be as cheap as possible which require antennas with small size, light weight, low profile and low cost, and that are easy to fabricate and assemble. A type of antenna that satisfies most of these requirements is the microstrip antenna. Most of the wideband techniques for microstrip antennas utilize complicated geometries such as stacked multiple metal/dielectric layers, complicated feed arrangements etc., which elude the primary attraction of microstrip antennas. On the other hand, single layer suspended configurations are considered the best choice as these are simple to fabricate and assemble. The objective of this research is to investigate simple microstrip antennas with large bandwidth. A single layer suspended microstrip configuration was chosen for the purpose. In the first part of the research, the bandwidth was increased to about 50% with linear phase characteristics by optimizing the feed configurations while retaining the overall simplicity. This study has resulted in proposing a criterion for obtaining maximum bandwidth in the suspended microstrip configuration. An analytical model has been developed for such an antenna configuration. Although several analytical tools are available for the microstrip antenna analysis, equivalent circuit based approach proves to be a simple one and offers convincingly accurate results. Another advantage of the proposed equivalent circuit modeling scheme is that it is suitable for computer aided design (CAD). In order to make this approach even more useful, the antenna designed in the first part was modified to meet desired specifications such as reduction in the air gap to make the antenna compact, symmetrical patterns, making antenna circularly polarized (LHCP or RHCP) without changing the feed configuration. Nearly symmetrical patterns were obtained throughout the band of operation by modifying the profile of patch close to the feed strip. Circular polarization (CP) operation has been obtained from the basic antenna by cutting a diagonal slot on the radiator patch. Here the slot orientation decides the type of CP i.e., LHCP or RHCP. In this work obtained of 7.1% axial ratio (3dB) bandwidth with other characteristics unaffected. The overall height of the antenna is reduced by 55% by cutting a slot and re-optimizing the feed strip dimensions. These studies emphasize flexibility offered by the design approach in realizing practical antennas for various applications.

Microstrip structures became very attractive with the development of cost-effective dielectric materials. Among several techniques suitable to the analysis of such structures, the discrete mode matching method (DMM) is a full-wave approach that allows a fast solution to Helmholz equation. Combined with a full-wave equivalent circuit, the DMM allows fast and accurate analysis of microstrips lines on multilayered substrates.   The knowledge of properties like dispersion and electromagnetic fields is essential in the implementation of such transmission lines. For this objective a MATLAB computer code was developed based on the discrete mode matching method (DMM) to perform this analysis.   The principal parameter for the analysis is the utilization of different dielectric profiles with the aim of a reduction in the dispersion in comparison with one-layer cylindrical microstrip line, showing a reduction of almost 50%. The analysis also includes current density distribution and electromagnetic fields representation. Finally, the data is compared with Ansoft HFSS to validate the results. / The German Aerospace Center has rights over the thesis work