Research On Wide Beamwidth Of Circularly Polarized Antenna

With the development of wireless communications, satellite navigation and positioning system plays an increasingly important role in the human society. Becausecircularly polarized waves have less multipath effects and strong anti-interference characteristics of rain and snow, circularly polarized waves are generally used for the satellite navigation and positioning system. Due to the request that a satellite antenna should have a uniform amplitude response within a region where the satellites can be seen, wide beamwidth antennas are mostly used. Wide beamwidthcircularly polarized antenna is put forward to overcomeabove problems, and there are broad prospects for their development.In this thesis, wide beamwidth circularly polarized antennas are mainly research.With three different ways to broaden the beamwidth, three final designs of the antenna structures with widebeam, good circular polarization characteristics are discussed.Although the three antennas operate in different frequency bands, theyall have symmetrical patternsin two main planes, and good radiation can be realized.The main contents of this thesis are as follows:The first chapter mainly introduces the research background and significance of wide beamwidth circularly polarized antenna, and their domestic and foreign researched status.The second chapter describes the basic knowledge of the theory of this article, including the work principle of microstrip antenna, the transmission characteristics of electromagnetic waves, conditions and methods of forming circular polarization.The third chapter designed a petal-shaped patch antenna for the needs of multi-mode navigation applications. This antenna has a dual-resonance characteristics, and it can cover the working bandsof Compass, GPS, GLONASS and Galileo.On both operating frequency bands, it has a wide half-power beamwidth and a circularly polarized beamwidth.Meanwhile, by adding back cavity design, an improved structure for this antenna is also proposed.The fourth chapterdesigned and tested a circularly polarized antenna working at 5.6GHz.By using a small disc which scattered the electromagnetic energy from the top just above patchto other directions, this antenna’sbeamwidthhasbeen effectively broadened.The antenna’s half-power beamwidthcan reach as wide as 200°. The antenna structure is simple, easy processing, low cost and practical.The fifth chapter designed an antenna working at 10 GHz. It not only has a wide beamwidthand good circular polarization characteristics, but also has a wide-band characteristics.Because for most circularly polarized antennas’ 3dB axis ratio bandwidth is narrower than their impedance bandwidth,there are a lot of restrictions in practicality applications. This paper designed a broadband antenna splitters to feed on the dual-port, thereby forming a broadband circular polarization.Thisantenna’s impedance bandwidth and 3dB axis ratio bandwidth are both 33%.The sixth chapter summarized the work in this thesis, and gave the future research directions to be carried out.