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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.

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.

The switched-beam antenna is one type of the smart antennas, which consists of the antenna array and the beamforming network. The four-beam smart antenna generates four beams to cover a 120¢X area, which can be used to improve the carrier-to-interference ratio and the frequency reuse of a cellular system. Due to the attractive features of microstrip antennas such as low profile, easy fabrication, and low cost, we use microstrip antennas as array elements. In this thesis, we propose a novel four-beam beamforming network which consists of a 4¡Ñ4 Butler Matrix and four 180¢X power dividers. This network is able to provide low side-lobe level. A modified Butler Matrix not only simplifies the circuit of the 8¡Ñ8 Butler Matrix, but also meet the requirement of the original Butler Matrix. From the result of measurement, the side-lobe level of each beam of the modified Butler Matrix is less than ¡V10 dB. We also show that this method is applicable to any Butler matrix.

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.

The purpose of this thesis is going to design a microstrip antenna that can detect the different tissue, according to this clue, we suppose that it can be used in medical application, for example to detect the breast tumor. Our research and guess are based on the different electrical properties of the tissue. Follow the conductivity and permittivity of different tissue, a simple 3D breast structure is going to be modelled, and a tumor tissue will be defined too. Four types of antenna have been designed and simulated in HFSS. The antenna with best performance will be manufactured, which is the rectangular microstrip antenna with gap, it works under 2.45Ghz resonate frequency, and with dimension 37.26mm×28.83mm. Test S21 of antenna in Vector Network Analyser with different biological tissue, in order to make a simple prove that the antenna can detect the different tissue. The result shows when we use the different tissue’s size and quantity, the S21 changes.

No / A coplanar edge-fed triangular patch antenna with an integrated stubline is proposed for harmonic rejection application. The design is aimed to achieve a good impedance matching to 50 ω at the fundamental frequency while suppressing radiation of the first and second harmonics. The antenna is attended to operate around 1GHz, with acceptable power gain above 1dBi and less than -15dBi at the harmonics. Simulated and measured results show a reasonable agreement.

With the rapid expansion of wireless communication services, ultra-miniature, low cost RF microsystems operating at higher carrier frequencies (e.g. 5-6 GHz) are in demand for various applications. Such applications include networked wireless sensor nodes and wireless local area data networks (WLANs). Integrated microstrip antennas coupled directly to the RF electronics, offer potential advantages of low cost, reduced parasitics, simplified assembly and design flexibility compared to systems based on discrete antennas. However, the size of such antennas is governed by physical laws, and cannot be arbitrarily reduced. The critical patch antenna dimension at resonance needs to be ~ λ_g/2 (where λ_g is the guided wavelength given by λ_g=λ₀/√(𝜖_r) . Several methods are available to reduce the physical size of the antenna to enable on-chip integration. A high dielectric constant substrate reduces the guided wavelength. Grounding one edge of the microstrip patch enables the resonant antenna length to be further reduced to ~ λ_g/4. However, these techniques result in degraded antenna efficiency and bandwidth. Nonetheless, such antennas still have potential for use in low power/short range applications. In this work, "electrically small" (small with respect to λ₀) square-shaped microstrip patch antennas, grounded on one edge by shorting posts, have been investigated. The antenna input impedance depends on the feed position; by adjusting the feed point, the antenna can be tuned to match a 50 Ω or other system impedance. The antennas were designed on a GaAs substrate, with a high dielectric constant of 12.9. The size of the patch antenna is further reduced by utilizing shorted through substrate vias along one edge. The size of the antenna is about 4.2mm × 4.2mm, which is ~1/13 of λ₀ at ~5.6GHz. The antennas are practical for integration on chip. Due to the size reduction, the simulated peak gain of the antenna is only −10.2 dB (~3.2% radiation efficiency). However, this may be acceptable for short-range wireless communications and distributed sensor network applications. Based on the above approach, integrated GaAs "chip-scale" antennas with matching power amplifiers have been designed and fabricated. Class A tuned MESFET power amplifiers (PAs) were designed with outputs directly matched to the antenna feed point. The antenna is fabricated on the backside of the chip through backside patterning; the PA feeds the antenna through a backside via. The structure is then mounted such that the antenna faces up, and is compatible with flip-chip technology. The measurement of a 50 Ω passive (no PA) antenna indicates a gain of -12.7dB on boresight at 5.64 GHz, consistent with the antenna size reduction. The measurement of one active antenna (50 Ω system) shows a gain of -4.3dB on boresight at 5.80 GHz. The other version of active antenna (22.5 Ω system) shows a gain of −2.9 dBi on boresight at 5.725 GHz. The active circuitry (PA) contributes an average of ~9 dB gain in the active antenna, reasonable close to the designed PA gain of 12.7dB. The feasibility of direct integration of a PA with an on-chip antenna in a commercial GaAs process at RF frequencies was successfully demonstrated. / Master of Science

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