| In recent years, with the rapid development of the modern wireless communication technology, the requirement of large capacity, high reliability and quality for the communication system is sharply increasing. Ever since 2002 when the US Federal Communication Commission(FCC) authorized the unlicensed use of UWB in the frequency band from 3.1 to 10.6GHz, the ultra-wideband(UWB) technology breaks the limitations in the exclusive military application, and has been widely used in the various commercial and civil applications. At the same time, the UWB technology provides a very promising solution for the long-lasting challenge of the high rate transmission in the conventional wireless communication systems, thus has become one of most competitive and promising research fields in the current wireless communication technology.As the key component of a wireless communication system, antenna is of crucial importance to the performance of the whole system. Therefore, the research of UWB antennas has a great significance on the design and development of UWB systems. The basic requirements for UWB antenna design include compact geometry size, low profile, wide operation bandwidth, moderate radiation efficiency and omni-directional radiation pattern. To catch up the rapid development of UWB technology, UWB antenna need have the following properties, including simple production process, low cost, and easy integration and good signal fidelity. Planar printed antennas, due to its low profiles, light weights and convenience in the conformal designs with the carriers, become a good candidate of UWB antennas. With the design goal of ultra-wideband printed antenna, and miniaturization and various bands of the wideband antenna, the dissertation mainly focuses on the automation design and optimization theory of the compact ultra-wideband planar printed antenna. Several UWB printed antennas and UWB antennas with band-notched characteristic with various geometry structures are proposed. The main contents and major contributions of the dissertation are summarized as follows.1. According to the design specification of the UWB antenna, a novel enhanced compact printed elliptical microstrip slot antenna with a CPW-fed elliptical patch is proposed. Its wide slot and resonant patch at the end of the microstrip line are both elliptical. The modeling, simulation and optimization process of the proposed microstrip antenna is elaborated in details, and the impact of the antenna geometry parameters on its impedance bandwidth is analyzed as well. The experimental and measured results show that the proposed antenna exhibits an impedance bandwidth over an ultra-wideband frequency range from 3.09 to 20 GHz with VSWR less than 2, which handily covers the whole UWB band. The antenna also shows omni-directional radiation pattern.2. The band notched methods for the UWB planar printed antennas have been summarized and analyzed. And then two band notched structures applied on the CPW-fed wide slot antenna for UWB applications are presented and discussed in details. By etching a U-shaped or V-shaped slot on the radiation patch, or adding another two L-shaped parasitic strips onto the wide slot in the ground plane, the various bands rejection could be obtained. Combining the usage of the three different kinds of structures, the single, dual and triple band-notched characteristic could be achieved respectively. The impact of the geometry parameters of the structures on the band-notched property of the antenna is further investigated. The experimental results indicate that the proposed antenna impedance bandwidth could cover the full UWB spectrum, while exhibits good band-notched characteristic in the rejected bands, which effectively eliminates the potential interfaces to the UWB system brought by the other communication systems.3. The automation design and optimization theory of the ultra-wideband planar printed antenna is investigated. And two novel automation design methods for the UWB antennas are proposed. The first one is to use the genetic algorithm to optimize the contour of the radiating patch of the CPW-fed UWB wide slot antenna, and a new design of UWB antenna is obtained. The second one is a kind of brand new automation design and optimization method, called shape blending algorithm. And the algorithm is applied in the optimization process of the patch contour of the CPW-fed UWB antenna. Both of the antenna prototypes got from the two design methods have been simulated, fabricated and measured. The experimental results show that the two prototypes could meet the design specification of UWB antennas. It also demonstrates the proposed design algorithms could be not only applied on the design and optimization on the UWB antennas, but also used in the design and optimization process of other various categories of antennas, which verifies the scalability, extensibility and universality of the proposed algorithms.4. The shape blending algorithm is further investigated on its application on the automation design of planar printed antenna for various wideband systems. A novel design of CPW-fed printed slot antenna is presented with its radiating patch shape given by the shape blending algorithm. A series of different curves could be obtained through the shape blending process. Then a corresponding series of printed antennas with different shapes of their patches are constructed accordingly, which have various impedance bandwidths. The antenna optimization process is discussed in details, and the impact of the antenna geometry formed by the shape blending algorithm on the antenna performance, specifically the antenna impedance, is also fully investigated and analyzed, which could serve as the guideline of the antenna design for various wideband applications. To verify the effectiveness and efficiency of the proposed algorithm, 6 antenna prototypes have been designed, fabricated and measured. The simulated results are compared with the measured performance, and show good agreement. The results demonstrate that the proposed type of antennas has a compact size and simple structures, and a stable gain is obtained as well. It also exhibits an impedance bandwidths range from 38.5% to 126.4% for VSWR < 2 by selecting various blended shapes, which provide a convenience for various wideband antenna designs.
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