Abstract. The problem of Electromagnetic compatibility is a popular topic. It is divided into two categories, one is conducted electromagnetic interference, another is radiated interference. We can use LISN to measure the signal of conducted electromagnetic interference , and use antenna to measure the signal of radiated interference. This paper will focus on the antenna. The frequency range of radiated Electromagnetic Interference measurement is so wide that using the halfwave dipole antenna will be very time-consuming, Therefore broadband antennas are often used in lieu of the halfwave dipole antennas. The design procedure of the log-periodic dipole array antenna is introduced in this article. Simulation data of such antenna using the NEC2 software, including the input impedance and the antenna pattern are also provided. Furthermore, based on the parameters obtained from the simulation, a log-periodic dipole array antenna can be fabricated. In doing so, the simulation results should be modified to take into considerations of the specification of the material used, such as diameters of the materials, and lengths of the transmission lines. Once the construction of the log-periodic dipole array antenna is completes, it can be compared with the simulation results, and the difference between them should be investigated to find out the optimal design parameters. Finally, the antenna factor can be calculated to compare it with the measurement data.

This dissertation introduces new and simple techniques for suppression of multispurious passbands, which are inherent to the conventional microstrip parallel coupleline bandpass filters. In addition, the operation of harmonic suppression is analyzed using a simple model. Special emphasis is placed on the applications of several new filter designs for microstrip diplexers and multiplexers. Compact, full-duplex beam scanning antenna transceiver systems with extremely broad bandwidth have also been developed. Recent advances in broadband monolithic microwave integrated circuit (MMIC) amplifiers make the realization of extremely broadband phased-array transceiver systems possible. The ultra-wideband phased-array transceiver systems can be used in multi-band mobile satellite communication systems and wideband radars. This dissertation presents a multi-band, compact, full-duplex, beam scanning antenna transceiver system for satellite communications and two designs of ultra-wideband, low-cost radar systems as applications of the MMIC amplifiers. In addition, a multi-frequency antenna has been developed. A single-feed triple frequency microstrip patch antenna is presented as an answer to the recent demand for multi-function systems in the wireless communications. In summary, the research presented in this dissertation covers every component required to build an ultra-wideband, full-duplex beam scanning phased-array antenna transceiver. The work done in this dissertation should have many applications in the wireless communication systems and wideband radar technologies.

Antennas design procedure, especially in portable devices, has been influenced by the growing demand for development of modern wireless communications. Hence, antennas that are wideband, compact, low profile, low cost, and easy to integrate into printed circuits are required. The research described in this dissertation focuses on optimally design and analysis of compact, low profile, and planar wideband patch antennas for modern wireless communications, namely, an open slot wideband planar antenna, a dielectric loaded wideband antenna, a planar antenna with ultra-wideband performance, and an E-shaped patch antenna. A novel very compact planar antenna with wideband performance is proposed and investigated. The proposed antenna has a size of only 9.2 mm x 9.8 mm x 1.52 mm. The size miniaturization is achieved by inserting an open slot in the ground plane to reduce the phase velocity. The antenna has achieved an impedance bandwidth of 52.16% and a stable radiation patterns over a wider bandwidth with a size reduction about 88%. Optimization of a dielectric loaded antenna by using Covariance Matrix Adaptation Evolutionary Strategy (CMA-ES) technique to achieve wideband and ii symmetrical broadside radiation performance is presented. Simulation is used to investigate the frequency-domain performance, regarding return loss, gain, and radiation pattern. Experimental measurements have also been performed to validate the performance of the proposed antenna. The obtained results show that the proposed dielectric loaded antenna achieves a good impedance matching and radiation characteristics in the entire band of WLAN IEEE 802.11a. A new ultra-wideband low profile microstrip antenna is presented for wireless applications. The proposed antenna has a compact size of 20x16 mm2 and an impedance bandwidth of 134.88% (3.5 GHz to 18 GHz). With the compact, ultra-wideband, and low profile, the proposed antenna can be a very good candidate for a wide range of communication applications. Spider Monkey Optimization (SMO) method is introduced for the first time for solving electromagnetic problems. The SMO is a new swarm intelligence technique which models the foraging behavior of spider monkeys. To show the efficiency of the SMO, different examples are presented and the results are compared with the results obtained using other popular optimization techniques. The optimization procedure is used to synthesis the array factor of a linear antenna array and to optimally design a rectangular and an E-shaped patch antenna for wireless applications. By comparing to traditional optimization techniques that reported in the literature, it is evident that SMO is efficient in reaching the optimum solutions with less number of experiments. The performance results obtained from study of these antennas show that these antennas can be an excellent choice for a wide range of wireless communication applications.

No / A new approach in achieving beam steering in array antenna is introduced using the genetic algorithm optimization. The binary switching technique uses simple binary ON/OFF diodes placed in the feeding network of the array element to achieve beam steering. Constantly feeding the driven element and continuous binary variation of the ON/OFF state of each parasitic array elements which determines its conducting ability defines a beam steering angle. Each beam steered angle is distinguished by series of binary combination determined by the genetic algorithm. A uniform circular array antenna consisting of 13 elements is used to implement this technique. The simulation and result analysis of the binary switched array is presented with several beam steering angles scanned.

No description available.

This thesis presents simulation data on array operation in wideband communication systems. It is shown that array structures with closer inter-element spacing outperform structures with much larger inter-element spacing. It is also shown that circular structures outperform linear structures. This performance difference between the classifications of arrays is due largely to the circular array's ability to handle high levels of interference. Even though a diversity combining scheme (MRC) was used in the simulator, the arrays provided interference rejection capabilities due to the closely spaced antenna elements. Though diversity does provide a gain in received signal, relative to the faded signal, realized diversity gain only comes about once interference has been mitigated. This thesis work showed that in an environment with a lot of interferers, the rejection of those interferers by an array is of utmost importance, even more than fading mitigation. / Master of Science

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24147号 / 工博第5034号 / 新制||工||1786(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 小嶋 浩嗣, 教授 山本 衛 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The aim of this project is to design a microstrip phase array antenna in ADS (Advance Design System) Momentum. The resonant frequency of which is 10 GHz. Two circular patches with a radius of 5.83 mm each are used in designing the array antenna. RT-DURROID 5880 is used as a substrate for this microstrip patch array design. These circular patches are excited using coaxial probe feed and transmission lines of particular lengths and widths. These transmission lines perfectly match the impedance of the circular patches. Various parameters, for example the S-parameters, two dimensional and three dimensional radiation patterns, excitation models, gain, directivity and efficiency of the designed antenna are obtained from ADS Momentum.

Novel printed monopole antennas, including diversity antennas, monopole array antennas and broadband antennas for WLAN operation, are experimentally studied and presented in this dissertation. These proposed antennas can be printed on dielectric substrates and practically integrated with system circuit boards by using printed circuit board technique. Also, the proposed antennas are low cost in fabrication and the reliability of system circuit boards can be improved. First, the design of the diversity antenna, which mainly comprises two substantially orthogonal printed monopoles and are placed symmetrically with respect to a protruded ground plane of T shape, shows good isolation between the two feeding ports of the proposed antenna. Second, the design of the printed array antenna, which comprises three equally-spaced equilateral-triangular monopoles, is proposed. Among the three monopoles, the center one has a larger size, which mainly controls the lower operation band, and the other two monopoles have a smaller size for higher operation band and show higher antenna gain and wider operating bandwidth. Finally, the quasi-self-complementary antenna is introduced. With compact size and wide bandwidth achieved, the proposed antenna is suitable for a mobile communication device, and can also provide good spatial diversity to combat the multi-path interference problem when mounting two proposed antennas appropriately spaced on a WLAN card.

Abstract Whether an Open Area Test Site (OATS) is qualified is based on the Normalized Site Attenuation (NSA). The purpose is to eliminate the influence of Antenna Factor (AF). Usually the AF provided by the manufacturer adopts the Standard Site Method (SSM) and is quoted from measurements at a 10-m range. In practice, the AF varies with the measurement conditions. This uncertainly will translate into error in NSA measurements. Currently radiated electromagnetic interference measurement mostly adopts the broadband antennas, and LPDA is one of the antennas used extensively. However, the AF provided by the manufacturer does not consider shifts in the phase center of LPDA with frequency. In the meantime the radiation pattern of LPDA is different from that of a short dipole. The investigation of this thesis will focus on these two parts. In determining the phase center of LPDA antenna we adopt the average shift of phase center to improve the AF. The numerical simulation results show that such an arrangement can result in improvement. We also use the method of PCPM (Phase Center and Pattern Matching) to modify the AF under different conditions of measurement when a ground plane is present. Our study, by using the numerical simulation and measurement, shows that this indeed improves the variation of AF over that obtained by SSM. In addition, efforts are also made to have a detailed discussion in mutually coupling effects between the LPDA antenna and the ground plane, in order to distinguish the impact on AF due to the coupling of the LPDA antenna and its image. Our numerical simulation results indicate that it does not have a significant effect.