Study Of Some Satellite Navigation Circularly Polarized Antennas

With the development of Chinese Beidou satellite navigation global systems,circularly polarized (CP) antennas have become a research hotspot. Two kinds of CPantennas are designed in this paper. One is the wide-beam CP antenna used for vehicleBeidou satellite navigation receiver system, and the other is the omni-directional CPantennas used for satellite signal reconnaissance and interference.First of all, a simple crossing dipoles antenna is designed and fabricated forBeidou I satellite navigation receiver system at S-band. In order to improve thebeam-width and low elevation performance, the dipole arms are bended and theantenna ground plane is reconstructed. The experimental results show that the gain isabout2.64dBi, the axial ratio is less than1.5dB in the maximum direction, and the3dBbeam-width is about135o. The antenna meets the user’s requirements.Another broadband CP receiving antenna is designed for Beidou II navigationsatellite system, and GPS, GLONASS as well. The antenna can operate on sevenfrequencies totally for the above three global satellite navigation systems. The antennagain at the elevation40o~60ois improved by changing the traditional conical spiralantenna to a special structure. According to the simulation results by HFSS, aprototype is made and measured. The VSWR is less than1.5:1in the whole band, theaxial ratio at the elevation20o~90ois less than2dB, and the3dB beam-widths inhigh and low band are about140oand155orespectively. The gain at the elevation30ois more than0.5dBi. It is shown that the antenna has good characteristics of thehemispherical radiation pattern.At last, two sets of dipoles are used to design an omni-directional CP antenna. Aspecial transmission line is adapted to get good impedance matching. The antennaworks at2.492GHz. The un-roundness and the axial ratio of the radiation pattern in thehorizontal plane are1.5dB and2dB respectively. The antenna gain is about2dBi.In a word, the above three antennas are all applied to Beidou satellite navigationsystems. With the development of Beidou satellite business, the proposed antennas willhave good extensive applications.