The Miniaturization Broadband Microstrip Antenna

One of humankind's greatest natural resources is the electromagnetic spectrum and the antenna has been instrumental in harnessing this resource. An antenna is a device that provides a transition from a guided wave on a transmission line to a "free-space" wave (and vice versa in the receiving case). Thus, information can be transferred between different locations. The rapid progress in communication technologies demands the integration of more than one communication systems into a single compact module. This indicates that the future communication terminal antennas must be compact and meet the requirements of multi-band or wideband to sufficiently cover the possible operating bands. It possesses the advantages of the low weight, the low-profile, and the conformability. However it suffers from the disadvantage of the narrow bandwidth. The technology of antenna miniaturization in the condition of increasing the bandwidth of the microstrip antenna is an interesting research.The main content of this thesis is compact wideband microstrip antenna. And the point of penetration is ultra wideband spiral microstrip antenna, which is the principle we carry on the design of the compact wideband microstrip antenna. A novel compact spiral antenna and the character of the novel spiral antenna as the spiral-mode microstirp antenna is discussed in theory, by simulation and experiment.The first chapter of this thesis is attached more importance on several parameters to describe the performance of antennas, the main analytical methods of the microstrip antenna. A brief introduce of the main work of this paper was also display.The main content of chapterⅡdescribes the microstrip antenna's miniaturization and frequency bandwidth extension technology. And their merit and demerit are described.In chapterⅢ, after describing the development and advantage of the ultra wideband spiral microstrip antenna, the design of a novel compact spiral antenna with gap-loading is presented. Compared with the traditional Archimedean spiral antenna, the area of the novel compact spiral antenna can be reduced by more than 30% without gain compromise. The AR (axial ratio) characteristic of the miniaturized novel spiral antenna at the low operation frequency isn't deteriorated, instead of a good improvement. And the radiation pattern of the novel compact spiral antenna is almost the same with the traditional Archimedean spiral antenna. We also studied the character of the novel spiral antenna as the spiral-mode microstirp antenna, and the results show that the area of the proposed spiral-mode microstrip antenna can be reduced by more than 30% without gain compromise. Finally, two methods of designing ultra wideband microstrip antenna are presented. One is the traditional ultra wideband antenna as the foundation of the ultra wideband microstrip antenna, the other is increasing the horizontal component of the electric field.