Design Of Miniaturized Multi-Band Circularly Polarized Beidou Antenna

With the step by step construction of BeiDou Navigation Satellite System, the demand for user terminal equipment is becoming more and more widely. Considering the requirements of terminal equipment portability, circular polarization characteristic of satellite signals and multi-band signal transmission of Beidou System, the antenna of portable terminal device should also have the characteristics of miniaturization, multi-band and circular polarization. Therefore miniaturized multi-band circularly polarized antenna occupies a very important position in Beidou user terminal equipment. Strengthening the research of the miniaturized multi-band circularly polarized Beidou antenna is imperative.Based on the analysis and comparison of the current typical miniaturized, multi-band and circular polarized microstrip antenna design method, two miniaturized multi-band circularly polarized microstrip antennas are proposed.Through the use of two independent feeding point and three layered patches, the first Beidou terminal antenna can cover the BDS-2 B1, BDS-1 L and S band. By using the corner-truncated method on the square patch, circular polarization can be realized. Based on the commonly used feeding method, two independent feeding point are used to realize the dual circular polarization and the metallized hole is introduced to increase the port isolation of the two common-grounded feeding ports. Four equal length slits are cut on the square patch edges to achieve miniaturization.The thesis analyzes the design process of the antenna structure, and simulates the influence of the antenna structure parameters on antenna performance. According to the conclusions and through the simulation optimization, the best value of the antenna structure parameters is determined. The final size of the antenna is 50 mm × 50 mm × 4.8 mm(0.26 λ × 0.26 λ × 0.025λ). Compared with the same kind of antenna, the proposed antenna covers the three frequency bands of Beidou system and the size is significantly reduced. The structure of the antenna is simple. The manufacturing process and materials used in the antenna are low cost. According to the simulation structure, the antenna is manufactured and tested. Simulation and test results show that the antenna can basically meet the requirement of the antenna performance of beidou terminals in each frequency band.Through the use of a single feeding point and the double layered patches, the second Beidou terminal antenna can cover the BDS-2 B1 and B3 band. By introducing perturbation of different length slits into the circular patch, circular polarization can be realized. At the same time, the CSRR structure is introduced to further reduce the volume of the antenna. The final size of theantenna is 60 mm × 60 mm × 5.8 mm(0.254 λ × 0.254 λ × 0.025 λ). Compared with the same kind of antenna, the proposed antenna covers the double frequency bands of Beidou system and the size is reduced. The simulation and test results show that the antenna has good impedance matching characteristics in each frequency band. The gain and axial ratio are basically meet the design requirements.