Study On Wide Beamwidth Antennas For Satellite Navigation Terminal System Applications

With focus on the using of space communication among the ordinary people, circularlypolarized (CP) antennas are employed both on satellites and in user terminals. In order to determineone’s absolute position anywhere on the earth (latitude, longitude, and altitude) at any time and inany weather, signal from satellites is supposed to be received continuously as much as possible bythe terminals. Wide beamwidth antenna is considered as an effective solution to this issue. Undersuch a technical background, a multi-step wide beamwidth bifilar helical antenna and a three-fedmicrostrip antenna with wide beamwidth circular polarization are proposed based on the theory ofhelical antennas and microstrip antennas. The main content of this dissertation is organized asfollows:Firstly, several main performances of the antenna are introduced, especially the parameter ofpolarization. At the same time, the key performance requirements of circularly polarized antennausing for space communication are given.Then, a multi-step wide beamwidth bifilar helical antenna is proposed. This antenna iscomposed of the spiral bifilar arms of two different pitch. The antenna’s radiation patterns, gain andaxial ratio(AR), are numerically studied by using computer simulations, and a set of physicalparameters provided excellent performance is identified. Providing near uniform pattern coverageover the entire upper hemisphere, the antenna exhibits wide3dB-gain beamwidth of159.1degree,3dB-AR beamwidth of130degree and6dB-AR beamwidth of160degree. The antenna ismanufactured and studied for their performance numerically and experimentally.Last, detailed theoretical analysis proves that a circular microstrip antenna, which is excited bythree central symmetrical feels with equal amplitudes and relative120degree phase shifts, canobtain good circular polarization characteristic. The proposed antenna can provide3dB-gainbeamwidth of90degree and3dB-AR beamwidth of95degree at1.75GHz, and3dB-gainbeamwidth of75degree and3dB-AR beamwidth of85degree at2.55GHz. At the same time, aOne-Three Wilkinson power divider is designed.