Research On BeiDou Antennas With Zero Phase Center

At present,china is stepping up the construction of the Compass Satellite Navigation System(CNSS)with independent intellectual property rights,which is expected to achieve global positioning coverage by 2020.The circularly polarization antenna that has the merits of anti-Faraday rotation effect and can effectively restrain the interference of rainy weather,is widely used in satellite navigation and satellite communication system.With the development of unmanned aerial vehicle and automatic driving,new requirements for the satellite navigation and positioning antenna are put forward.In order to achieve high positioning accuracy,the antenna must have stable phase center and the deviation between the phase center and the geometric center of the antenna must be as small as possible;And integrated positioning technology can be used to eliminate the positioning error,that requires the antenna with broadband characteristic,so that it can cover several bands of multiple satellite navigation systems;In order to receive the weak satellite signals and realize the location anywhere on earth,the antennas are required to have high gain at low elevation angle and wide 3-dB axial ratio beamwidth in wide frequency band.To reduce the effect of the multipath signal from the ground reflection and the scatterer scattering,the antennas are required to have the ability to counteract the multi-path response.The miniaturization of the antenna is also an important development trend,research about miniature antenna with a stable phase center is an important research topic.The main research content of this paper is the design of the Beidou antennas with zero phase center,focusing on the research about the factors that affect the deviation of the phase center,and several methods is put forward to reduce the deviation of the phase center.According to the requirements and characteristics of the Beidou satellite navigation system,we also research on how to improve the gain at low elevation angle,3-dB axial ratio beamwidth and the ability of anti-multipath effect based on zero phase center antenna,and study the antenna miniaturization technology.The main research points and innovation points in this paper are as follows:Firstly,a broadband,wide beamwidth,zero phase center satellite navigation antenna is designed.The antenna is fed by four center symmetrical feeds to reduce the deviation of the phase center.And the gain at the low elevation angle and the 3-dB axial ratio beamwidth can be improved by loading two different radii metal rings and a stepped cylindrical copper wall.Secondly,a series of microstrip patch antenna with zero phase center is designed,the structure of the antenna is very symmetrical,that can minimize the influence of the perturbation on the phase center of the antenna.Two antennas use the square patch structure with four slits,which are fed by a diagonal feed and a center feed with an annular slot,respectively.Another antenna uses a novel central feed structure with double annular slots to realize zero phase center circularly polarization radiation.Based on the central feed structure,two miniature antennas with small phase center deviation by embedding symmetric slits and loading tabs on the slits are studied.Finally,a low profile,broadband and wide axial ratio beamwidth satellite navigation antenna is designed.The antenna is a single board structure,which can maintain a relatively large axial ratio beamwidth in a wide frequency band.And using this antenna structure as the radiator,a choke ring antenna with corrugated ground plane is studied.