Dual-Polarized Microstrip Antenna Arrays And UWB, Multi-Band Printed Antennas

To meet the urgent requirements of national economy and military applications for the microwave image SAR (synthetic aperture radar), electronic warfare systems and wireless communications, etc., this dissertation makes a deeper study on several types of antennas, including the broadband dual-polarized microstrip antenna arrays for SAR systems, the UWB (ultra-wideband) printed antennas for electronics warfare and UWB communication systems, and the multi-band printed antennas for WLAN (wireless local area network ) applications. Several novel designs are proposed and their experimental verifications are completed. Four main subjects are included:Firstly, several novel broadband dual-polarized microstrip patch antennas are comprehensively studied. From theory and experimental results, the bandwidth, isolation and cross-polarization characteristics of a dual-polarized microstrip patch element with various feed structures are analyzed in detail and compared, then how to effectively choose the element for the dual-polarized microstrip antenna array design is discussed.Secondly, an X-band 16xl6-element broadband dual-polarized microstrip array is developed. Its measured impedance bandwidth is larger than 20%, the isolation between two ports higher than 47dB and the cross-polarized level below -37dB, which have arrived at the international levels. In addition, based on the element design, various feed networks are further studied by using the even/odd theoretical analysis with the experimental verification, where the affections of the networks coupling, the feed-line parasitic radiation and the space limitation are adequately considered to improve the isolation and cross-polarization characteristics.Thirdly, a test novel UWB printed antenna is developed, which achieves a measured impedance bandwidth better than 21:1 and a stable radiation pattern with a simple structure and a compact size, which keeps ahead in the world. Here the new idea of using the printed antenna with basically two-dimension to replace the conventional three-dimensional disc-cone antenna with a larger volume is proposed, where a trapeziform ground plane, a elliptical monopole and a tapered CPW feeder are used to replace the cone, a disc and the coaxial line, respectively, resulting in a miniaturized volume, simple structure and easy integrating with the active circuits, and achieving further broadband performance. Moreover, a cavity-backed microstrip slot antenna is also proposed to achieve a directional radiation and effectively reduce the ground plane's size, which expands the applications of the microstrip slot antenna. A test wideband UHF-band microstrip slot antenna has been developed with a compact size.Finally, a dual-band WLAN microstrip antenna is proposed for the WLAN system application, where a T-shaped slot is used to realize the dual-band operation with a higher gain. Simultaneity, a tri-band printed monopole antenna is also developed to meet the demand of WLAN phone antennas, which adopts the multi-branch design to complete the tri-band operation with a compact size and the omnidirectional radiation characteristic.