| Because of wide coverage, accurate positioning and all weather operations abil-ities, satellite navigation systems have broad prospects. As an important channel to transmit microwave, antennas are playing an important role in satellite navigation sys-tems. The antennas are required to possess broad beamwidth and circular polarization by the satellite navigation system. Based on traditional microstrip antenna, a broad beamwidth and circularly polarized microstrip antenna for multiband GPS/BDS is de-signed and studied in this dissertation.This dissertation is mainly divided into four sections. First section introduces the research review and current status of antennas in Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS). Antennas with broad beamwidth, circular polarization and multiband are introduced, respectively, aimed at the characteristics of antenna in satellite navigation system. Basic knowledge, analysis method and methods to achieve circular polarization of microstrip antenna are also introduced.Second section proposes a new structure of broad beamwidth and circularly po-larized microstrip antenna working at single band based on the existing methods of beamwidth enhancement. Single-band and circularly polarized microstrip antenna with165°-3dB beamwidth is achieved by using big dielectric substrate, rectangular dielec-tric wall and metal ring. Sample of the antenna is fabricated. Measured results meet well with the simulated results.Third section theoretically analyzes proposed antenna in the second section. At first, the hypothesis of loading metal lines acting as directors or reflectors is proposed. Secondly, the concept of rectangular metal ring loaded on the microstrip antenna equiv-alent to four metal lines is discussed. Next, the analysis model of metal lines loading on single-band circularly polarized broad beamwidth microstrip antenna is established. Finally, the radiation fields of analysis model are calculated using moment method and electric field integral equations. The comparison of calculated results and simulated re-sults proves the correctness of analysis model and method of beamwidth enhancement.Fourth section achieves broad beamwidth and circularly polarized multiband mi-crostrip antenna based on the methods of beamwidth improvement developed in second section as well as multiband realization techniques. The antenna covers five bands of GPS/BDS and exhibits broad beamwidth and circular polarization in each band. Finally, it is shown that measured results of the antenna meet well with the simulated results. |
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