| The GNSS needs to satisfy the necessities of multiple navigation systems,and the multi-frequency and wideband antennas in the receiving system can fulfil this action.In this thesis,the realization of multimode,wide beam,micromation,broadband circular polarization antenna is studied and designed according to the requirements of the subject.In this thesis,multi-band,wide-beam,micromation and wideband skills of navigation antenna are intended according to the necessities of the motive.The research content of this thesis consists of the following three units.In order to realize the multi-mode operation of Bei Dou Navigation Satellite System,a printed four-arm spiral antenna working in BDS B1 frequency is firstly designed,which is fed by a four-string feed network.The results show that the bandwidth of traditional single-frequency four-arm spiral antenna is narrow near the resonant point.Then the impedance bandwidth covers the B1 and B3 frequency by parasitising another radiation arm on the basis of each radiation arm.The axial ratio bandwidth of antenna are 175° and148° at 1.268 GHz and 1.561 GHz.The maximum gain are 6.6d Bi and 5.2d Bi.The beam width are 106° and 111°,and the gains are 0.5d Bi and 0.7d Bi at 20° elevation,the front to back ratios of the antenna are 17 d B and 22 d B respectively,which meet the design requirements of the high-precision Beidou navigation satellite antenna.In order to realize the multi-frequency compatibility of GPS,the multi-feed method is selected to design the dual-frequency microstrip laminated antenna applied to GPS L1 and GPS L2,so that the antenna can obtain more than 130° axial ratio beam width.However,the structure of the stacked antenna is large,so the RIS structure is designed to be placed on the upper layer of the feed network,so as to implement the down-sizing of the antenna,and the final antenna size is.In order to implement the conformal pattern of navigation antenna and platform carrier,a square diameter embedded cavity is designed for the antenna,and the surface is covered with a conformal wave-permeable composite material.After loading the embedded cavity,the axial ratio bandwidth of the antenna is increased to47%,and the 3d B axial ratio beam width is increased to more than 180°,which solves the problem of the mutation of the antenna’s axial ratio and gain value in the middle frequency band,and improves the forward and backward ratio of the antenna’s 3d B axial ratio beam width at low frequency and high frequency,so as to ensure the application requirements of GPS navigation antenna.It does not affect the aerodynamic characteristics of the carrier platform.The techniques of lowering the antenna profile and broadening the bandwidth are studied,and a low profile broadband antenna fed by coplanar waveguide compatible with four satellite navigation systems is proposed to achieve the goal of working in broadband in limited space.Alloy band and orthogonal metal piece are burdened on the feed vector of the antenna,and the impedance corresponding frequency band reaches 55.3%.Two rounded polarization techniques were created by half-ring metal band and t-groove on the square groove,and the axial ratio bandwidth was increased to 60% by building quartering microstrip plates and gyroidal gaps on the floor to make the surface current plainly distributed on both brims.The antenna gain is stable and about 4d Bi in the whole working bandwidth.In addition,the antenna is formed into a binary array by using the principle of superposition of the directional pattern to correct the asymmetry of the directional pattern,and the ratio of front to rear of the antenna is improved by adding a reflector plate under the antenna.Finally,the antenna unit is machined and tested,the measured bandwidth reaches 54%,and the test gain is basically consistent with the simulation results. |
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