| With the development of communication technology,satellite navigation communication has been widely used.Satellite navigation system for a long time the terminal antenna multipath suppressed performance is becoming a hot spot of research,from the source to eliminate the influence of the multipath signal navigation system positioning accuracy.Multipath signals are mainly derived from left-handed circularly polarized waves generated after primary reflection.Therefore,in order to improve multipath suppressed performance,the terminal antenna needs to have a wider 3-d B axial ratio beam width(ARBW)and a larger front back ratio(FBR)in order to reduce the cross-polarized radiation at low elevation and backward direction and inhibit the reception of left-handed circularly polarized waves.Therefore,based on the patch circularly polarized antenna,this thesis proposes a design method to improve its anti-multipath performance.The main achievements are as follows:(1)A single-frequency multipath suppressed satellite navigation antenna suitable for GPS L1 band is proposed.Firstly,a slotted floor and loaded with metal probes can broad3-d B ARBW from 160° to 203°,which effectively suppressed the interference of multipath signals at low elevation.On this basis,by loading metal curved branches,the FBR of the antenna is increased from 8 d B to 26 d B,which effectively suppressed the backward cross-polarized radiation,and finally realized the single-frequency satellite navigation antenna with strong multipath suppressed performance.(2)A dual-frequency multipath suppressed satellite navigation antenna suitable for BDS B1 and B2 bands is proposed.Firstly,the 1.207 GHz 3-d B ARBW is broadened from 166° to237° by means of floor sloting.Then,the 3-d B ARBW of 1.561 GHz was widened from 116°to 195° by loading two rings of metal bent branches,which effectively suppressed the multipath interference at the high frequency and low elevation.Meanwhile,the FBR at the dual-frequency points was also effectively improved,where 1.207 was included.The FBR of GHz increased from 14.1 d B to 18.86 d B.The FBR of 1.561 GHz is increased from 15.73 d B to 24.85 d B.Finally,the FBR of 1.207 GHz is further increased to 20.02 d B through the short-circuit needle loading technology,which effectively inhibits the backward cross-polarization radiation and realizes the dual-band satellite navigation antenna with strong anti-multipath performance.(3)A wideband miniaturized feed network with flat output amplitude and phase is proposed.The network consists of a wideband miniaturized hybrid coupler with flat output amplitude and phase and a trans-directional(TRD)coupler.Among them,the broadband miniaturized hybrid coupler is composed of open/short route loaded three-period T-type transmission line and short-circuit parallel coupling line of branch loading terminal.The hybrid ring is theoretically analyzed by equifying the open/short route loaded three-period T-type transmission line to 90° branch loading terminal short-circuit parallel coupling line to270° transmission line.On this basis,the hybrid ring is connected with the TRD coupler to realize the broadband miniaturized feed network with flat output amplitude and phase.The test results show that the 10-d B impedance bandwidth of the feed network is 35.5 %,and the amplitude difference between the output ports in BDS B1 and B2 bands is less than 1 d B,and the phase difference is 90° ± 5°,which can provide high purity circular polarization excitation for dual-band antenna... |
