| Ultra-wideband is a novel wireless communication technology. It has extensive application in modern wireless systems such as ultra-wideband communication system, ultra-wideband radar system and ultra-wideband electronic reconnaissance system. With the rapid advancement of ultra-wideband system, the ultra-wideband electronic devices develop towards miniaturization direction, which requires development of the responsive ultra-wideband miniature antenna.In this dissertation, several novel ultra-wideband miniature antennas are proposed on the basis of circular disc monopole. The impedance bandwidth, radiation characteristic and other aspects of the antennas can satisfy the communication requirements. All of them are studied through different means such as theoretical analysis, simulated design, and experimental measurement. As the theoretical basis of the entire dissertation, the reason why the circular disc monopole has good impedance characteristic within the ultra-wide bandwidth is researched using three models. According to the travelling wave and standing wave model, the antenna operates in a standing wave mode at lower frequencies and in a travelling wave mode at higher frequencies. The bandwidth of the antenna is broad because the existence of the travelling wave mode. According to the multiple-ring and multiple-resonant model, the circular disc monopole can be considered as the superposition or complemental composite of multiple rings. The overlap of numbers of related resonant modes makes the antenna has ultra-wide bandwidth. According to the tapered line model, the circular disc monopole antenna is similar to the antennas which are composed of the exponential, triangular, Klopfenstein, and parabolic tapered line. As the wideband impedance matching characteristic of the above tapered line is good, the circular disc monopole itself can also get very wide impedance bandwidth.The circular disc monopole antenna has excellent electrical characteristics. The analytic results show that it has 10:1 impedance bandwidth at least and omnidirectional radiation pattern. Meanwhile, it can be able to radiate and receive the short pulse signals without distortion. Although this antenna has many advantages, it consumes very great volume space as the ground plane is perpendicular to the radiator. In order to improve this performance, the planar circular disc monopole is proposed. The structure reduces the space size of the ground plane greatly. And what's more, the planar antenna's size can be further reduced by cutting a certain length, puckering a certain length or rotating a certain angle. In order to solve the problem of the antenna's wind load, the ultra-wideband ring-shaped monopole antenna is proposed. The single-ring and multiple-ring structures can both improve the wind resistance capability while maintaining the basic characteristics of the antennas. The large-scale ring-shaped monopole antenna is designed by using similarity theory. It has broader practical value. Though only one ultra-wideband antenna can cover ultra-wide bandwidth, different application conditions require for different antenna bandwidths. For this reason, the circular disc and ring-shaped monopole antenna with wavy-edge which can reject the higher frequency is proposed. The antenna's bandwidth covers a frequency range from 3.1 GHz to 10.6 GHz more or less, and it is just the civil ultra-wideband communication range. The antennas mentioned above are designed to satisfy different demands by changing the shape or structure of the antenna to achieve the miniaturization objective. In addition, the antenna's miniaturization can also be realized by loading with resistances. The fundamental aim of the method is to change the surface current distribution. For the resistive loaded circular disc antenna, the resistances are loaded on both sides of the circular disc. The current distributed at the end sides of the antenna is absorbed by the resistances. Then low-frequency signals' amplitude is reduced and the low-frequency is expanded, which is as a matter of fact to reduce the size of the antenna.The tapered line theory in circuit can be applied to the design of the special-shaped monopole antenna in order to obtain better electrical characteristics. So the circular disc monopole antenna is optimum designed and a novel Klopfenstein taper monopole antenna is proposed. The impedance matching characteristic of the Klopfenstein tapered line is the best, and the Klopfenstein taper monopole antenna is designed based on it. The antenna's electrical characteristic is similar to the circular disc monopole. On this basis, the coplanar waveguide-fed and microstripline-fed planar Klopfenstein taper monopole antennas are designed. The simulation and measurement results prove that the Klopfenstein taper monopole antennas have small size and good performance. And the planar printed antenna can be convenient integrated with other radio frequency circuits. The idea to design antenna by using of tapered line theory directly can be used in practical operations.The main purpose of this dissertation is to solve the problem of the ultra-wideband antenna's miniaturization. Several principles and methods are proposed, and the corresponding antennas are made and measured. Then the essential analytical results are obtained. The ultra-wideband miniature antenna proposed in this dissertation is mainly used for the civil ultra-wideband communication, and its frequency rang is 3.1~10.6GHz. But the research results can be promoted to wider band in order to provide consultation for military and civil requirements.
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