| With the continuous progress of science and technology and the increasing demand for wireless communication applications,satellite navigation and positioning plays an important role in many fields.At present,there are four kinds of satellite positioning systems: Global Positioning System(GPS)in the United States,Beidou satellite positioning system in China,GALLILEO system in Europe and GLONASS in Russia.The impedance bandwidth,axial ratio bandwidth,beam width and stability of phase center of navigation antenna directly affect the positioning effect of navigation equipment.At the same time,portable navigation equipment requires the antenna to have the characteristics of miniaturization,broadband and high gain.Therefore,it is of great significance to develop GNSS antennas that meet the needs of many parties.In this paper,the corresponding research and design are carried out according to the requirements of GNSS navigation and positioning antenna.Firstly,the basic index of antenna design and the realization of circular polarization are studied,and the antenna performance optimization methods are described in detail from three aspects:wide frequency band,wide beam and miniaturization.Then,the basic knowledge of fractal is introduced,and a design scheme that can improve antenna performance by combining fractal structure is put forward according to previous research experience.At the same time,the basic concept and determination method of antenna phase center are given.Based on the theoretical basis and practical application requirements,three navigation antennas and a filter antenna are designed.Because microstrip antenna is easier to realize miniaturization,all antenna design schemes in this paper are based on microstrip antenna.To realize the miniaturization of the antenna as much as possible under the condition of ensuring the antenna performance,a fractal structure is introduced into the design of the navigation antenna.At the same time,the three navigation antennas are highly symmetrical in structure,which can ensure the antenna has a stable phase center.Firstly,two single-frequency navigation antennas are designed,the center frequencies are 1.561 GHz and 1.575 GHz,respectively.The 3d B axial ratio bandwidth,impedance bandwidth,and gain all meet the requirements,and the phase center is stable.According to the requirement that multiple navigation systems need to work together in practical applications,a dual-frequency navigation antenna is further designed,which has a stable phase center,an axial ratio,and impedance bandwidth including two working frequency points.At the same time,the filter antenna is designed to improve the anti-interference of the navigation antenna.Due to the time,only the preliminary design of this type of antenna has been carried out at present,and the working frequency band of the antenna has not been adjusted to the navigation frequency band.The preliminary designed filter antenna is a narrow-band filter antenna working at 5.1GHz frequency,which can be applied to indoor wireless communication systems.The antenna has good frequency selectivity,stable gain in the passband,and a small size.The research on this antenna provides a preliminary design idea for designing navigation antennas with anti-jamming characteristics in the future.Ansoft HFSS 15.0 is used to simulate and verify the designed antenna.All four antennas are made in kind and tested to confirm their actual working performance.The test results of the antenna are consistent with the simulation results,which has important practical application value. |
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