Research On Multimode Ship-borne Beidou Navigation Terminal Antenna

The rapid development of the BeiDou Navigation Satellite System provides more possibilities for multi-mode navigation terminal antennas.On the other hand,with the rapid development of the transport industry,the number of ships has increased dramatically and the channel is getting crowded,which has placed higher requirements for ship positioning and navigation accuracy.The receiving antenna should cover as many modes as possible,and can be switched to other satellite positioning systems if necessary to ensure stable and uninterrupted operation of the positioning system.At the same time,the axis ratio beam width(ARBW)and the half power beam width(HPBW)are also required to make sure that wireless signals can be received at any position on the earth.Wide-beam antennas are often designed with helical antennas and dipole antennas,but the size of these antennas is relatively large.However,the beam width of conventional patch antennas is too narrow to meet the shipboard requirements,and thus let it have a certain research value.In order to meet the needs of shipborne antennas,a design method based on the microstrip antenna to broaden the dual-band beam width is proposed.The main innovations of the paper are listed as follows:(1)A method for designing widen the axial ratio beam width of the antennas by using the parasitic element on the floor is proposed.A four-fed dual-band stacked circularly polarized antenna was designed for the B1 and B2 bands of Beidou II.The simulation results show that the inner ring annular metal strip,the combination of the outer ring metal strip and the resistor can realize the broadening of the dual-band axis ratio beam width.The antenna with frequency of 1207 MHz has ARBW of 204°.At the frequency of 1561 MHz,the ARBW is 215°,meeting shipboard application requirements.(2)A method for designing widen the half power beam width of the antennas by loaded circular metal strips and reduced the size of floor.A four-fed stacked antenna is designed for the Beidou ?.After comparison and analysis,the inner and outer rings are loaded with four segments of annular metal strips,and placed on the upper dielectric material has the best structural properties.The size of the floor and the annular gap of the inner ring can widen the beam width of the high frequency band,while the outer ring annular gap has a greater influence on the beam width of the low frequency band.The simulation results show that the HPBW with the center frequency of 1207 MHz can reach 131°,and the HPBW with the center frequency of 1561 MHz can reach 130°,which realizes the broadening of the half power beam width in dual-band.That satisfies the practical application of the Beidou navigation terminal antenna.(3)The feed network is designed by Trans-directional coupler,and the impedance bandwidth of the above two wide beam antennas is broadened.Simulation and test results show that the antenna can cover the satellite navigation working frequency band of BDS,GPS and Galileo while maintaining the characteristics of wide beam.By using a four-capacitor distributed TRD coupler,the port output phase difference is improved and the phase is flatter,maintaining good circular polarization characteristics of the antenna at the same time.The antenna has a simple structure and easy to produce.Due to the above reasons,it may has practical application value.