Study On Dual-Polarized Dielectric Resonator Antennas And Low-Sidelobe Circularly-Polarized Microstrip Arrays

The earth observation technology has been listed as one of the top ten leading techniques that were planned in advance in the 11th Five-year Plan by the"National Scientific and Technical Plan Outline in the Long and Medium Term (2006-2020)"of China. As an important remote sensing technique, the SAR (Synthetic Aperture Radar) system is featured by all-time and all-weather capability and high-quality image, which has found wide applications in both military and civilian systems. This dissertation is dedicated to the detailed study on the dielectric resonator antenna for dual-band dual-polarized (DBDP) array applications. Under this background, a novel design for DBDP arrays is proposed. On the other hand, low-sidelobe circularly-polarized microstrip arrays for RFID applications are studied. The main contents are outlined as follows:Firstly, this dissertation makes an overview on various techniques of dual-polarized dielectric resonator antenna (DRA) in the recent years, discusses the advantages and disadvantages of these techniques, then presents a comparision and the conclusion. It also makes an overview on shared-aperture DBDP arrays for SAR applications in the recent decade. The overview highlights the evaluation of different designs associated with their technical specifications and leads to conclusions on the design approaches and considerations. In addition, this dissertation introduces an overview on antenna techniques for RFID Readers.Secondly, the dissertation provides a detailed coverage on the design of dual-polarized DRA, the influence of shape, size and other parameters of DRA on the antenna performance, and the improvement of cross-polarization performance through a balanced excitation method. Parametric studies of balance-probe-feeding and balanced-slot-feeding are presented. The experimental antenna was fabricated. The measured impedance of 7.9% and 11.8% (S11≤-10dB) are achieved at horizontal and vertical polarization, respectively. The isolation is larger than 35.9dB from 5.46GHz to 5.9GHz, which reaches the international advanced level.Thirdly, a novel design for shared-aperture S/X DBDP DRA arrays is proposed which combines S-band microstrip dipoles and X-band DRAs in an interleaved manner to achieve the frequency ratio of 1:3 in a shared-aperture configuration. In the design of X-band DRA, the balanced-slot-feeding technique is applied to improve the port isolation and reduce the cross-polarization level. The simulated cross polarization levels are -32dB and -47.5dB at S and X band, And the±24°phase scanning performance is achieved for one dimension with the horizontal polarization.Finally, the low-sidelobe circularly-polarized microstrip array for RFID application is developed. The simulated results of a experimental antenna are in good agreement with the measured ones. The measured sidelobe level of -21 dB in the horizontal plane was measured at the frequency of 2.56 GHz with the measured axial ratio of 1.1 dB.