Research On The High-precision Antenna And Its Multipath Mitigation Techniques In Satellite Navigation Systems

High-precision antenna is not only an important part of the Global Navigation Satellite System(GNSS)ground reference station,but also an indispensable device for various GNSS high-precision measurement systems.As a RF device of high-precision satellite navigation receiver,high-precision antenna should be full-band,full airspace,without distortion to receive satellite signals,to minimize the antenna non-ideal characteristics of the introduction of measurement error.On the other hand,to reduce the signal processing pressure of the receiver,high-precision antenna should also have good multipath suppression.With the rapid development of GNSS,high-precision antenna research in the multi-path assessment and suppression theory and antenna technology are faced with some new problems.In this paper,the demand for high-precision antenna in the construction of Beidou Navigation System(BDS)is applied,the theory of multi-path error assessment and elimination in the actual receiving environment of the antenna,L/S band high-precision antenna integration technology and miniaturization technology are studied,the main research results are as follows:(1)Being an error source interaction with antenna and environment,it is a key problem to establish an error assessment approach in actual receiving environment.Accoding to electomegnetic theory on rough surface and Fresnel transmission theory,we analyse the multipath model of city and banlieue.Based on this,we proposed an error assessment of multipath with semi-open model.The proposed method of using the distance between the control antenna and the violent undulating terrain to eliminate the tilt reflection multipath is proposed.Finally,according to the criterion,the performance constraint of the multipath suppression ability of the antenna is proposed.The above research can provide important reference for the application of various GNSS ground fixed stations and antenna installation with high precision measurement in the field,and provide the theoretical basis for the realization technology of high precision antenna.(2)The frequency coverage of the antenna is the basic requirement of GNSS monitoring system,and it is also the prerequisite for system-compatible interoperability.In order to cope with the Bs band of Beidou system,this paper proposes an integrated high-precision antenna with L-band and S-band technology.Antenna with four-arm spiral antenna and patch antenna combination of radiation elements,to maintain the independence of the performance between the band.In the design of L-band radiator,a four-arm spiral antenna with high radiation efficiency is proposed by using the gradient transmission line impedance matching theory.Finally,a multi-band hybrid choke is designed for the balanced antenna anti-multipath capability and low elevation angle satellite reception capability.The simulation and the measured results show that the integrated high-precision antenna in the L-band and Bs band,respectively,to achieve 1mm and 2mm within the phase center change(PCV),in the cut-off angle(elevation 10 degrees)above 2dB and 4dB within the circle Polarization axis ratio.In the multipath suppression capability,the L-band and the Bs band have 30 dB and 22 dB gain ratio(FBR),respectively.(3)As the best-known antenna anti-multipath technology,choke ring is too large volume and weight is the biggest obstacle to its application,this paper presents a miniaturized choke technology to expand the application of high-precision antenna.The miniature choke is designed based on the vertical choke ring,with reflection cavity edge serrated.Combined surface wave suppression of choke ring and the ability of the sawtooth structure to disturb the cavity surface ring current effect,the cross-polarization of the radiation level are reduced.The new choke has the same performance as the three-dimensional choke in the L1 and L2 bands,and the performce at L5 band is slightly beyond it.(4)Since the high-precision antenna is still difficult to effectively eliminate the short-time strong multipath signal near the horizontal plane,this paper improves a new anti-multipath technology with absorbing material.A metal plate is applied to shield multi-path signal near horizon,and the use of absorbing material to suppress the metal surface itself generated reflection,reducing the antenna phase fluctuations.In this paper,the working mechanism of the absorber is analyzed,and a set of design criteria for optimizing the absorbing shield is proposed according to the theoretical analysis.The measured results show that the absorbing plate can increase the multipath suppression ability of the antenna by more than 40%.Furthermore,it is proposed to replace the traditional sponge or rubber absorbing material with electromagnetic absorbing metamaterials,so that the absorber has a lighter structure and more robust environmental adaptability.Part of the research results has been successfully applied to the Beidou satellite navigation system monitoring station high-precision receiver and other projects,such as L/S band integrated high-precision antenna and absorbing shield technology.Other research results will play an important role in the future system construction,such as semi-open multi-path error assessment.In addition,due to the excellent performance and low cost,miniaturized high-precision antenna has a broader application prospects.