Research On Mitigation Of Multipath And Jamming Based On Polarization-Sensitive Antennas And Distributed Array

High precision measurement and confrontation technologies in complex electromagnetic environment have become the key to restrict the service of satellite navigation system.For the user segment,by using polarization diversity,and adding the polarization domain information processing on the basis of the space-time domain processing,the multi-polarized antenna can increase the degree of freedom of the antenna(array),realize the miniaturization of the subscriber antenna,and enhance the performance of small-scale antenna of high-precision measurement and multi-path,interference suppression.For the control section,the small distributed array with diameter antenna reducing the requirements of traditional antenna on the antenna power,array form and installation.It is conducive to enhance the construction flexibility of the ground station.It also can realize the multi-target tracking and single target enhancement capability of the ground station under the premise of miniaturization of the antenna.The paper carried out the following four aspects of research work:(1)In order to solve the problem of the miniaturized antenna with high precision in the normal receiver,a high precision antenna technology based on polarization diversity is proposed.The polarization model of circular polarized microstrip patch antenna is established.The radiation characteristics of the orthogonal feed antenna are analyzed from the radiation mechanism.Further,the conventional analog feeder network is converted to digital adaptive by using the polarization diversity reception.Under the condition of the known diection of arrived signal,single patch antenna can achieve a wide beam and a stable phase center,and the polarization diversity of the signal to the wave direction has a certain fault tolerance at the same time.By using the finite element method,it can be verified that the gain of the rectangular microstrip antenna is less than 2dB and the phase center stability is about 0.05 mm in the range of 80 ° elevation angle.Compeared to conventional antenna with same phase center stability,the size of antenna by polarization diversity can be reduced by half times while beamwidth is increased by 70%.(2)The conventional signal processing method can-not mitigate the short delay multipath signal in the presence of the direct signal,and lacks the detection means for the long delay NLOS signal when the direct signal is not present.In order to solve the above problems,and realize the miniaturization of the anti-multipath antenna in the normal receiver,a multipath signal detection technology based on orthogonal dual-line polarized antenna is proposed.The reflection and polarization characteristics of the multipath signal are analyzed.By using the characteristics of poor polarizied axis of strong multipath,the two polarization components of the signal are simultaneously received by the single antenna orthogonal polarization,and the detection of short delay multipath is realized by parallel correlation cancellation processing,and furthermore,the multipath signal mitigation is achieved based on detection results.Theoretical analysis and simulation show that the polarization coherent cancellation receiver can effectively detect the short delay multipath,and multipath error envelope is reduced by more than 75% after multipath mitigation.The proposed theory is also useful for long delay NLOS signal detection.(3)In order to solve the problem of anti-jamming with miniaturized antenna array when interference and signal come in the same direction,an anti-jamming technique based on planar orthogonal dual-polarizied antenna array is proposed.The spatial and polarization characteristics of orthogonal dual-polarized antenna array are analyzed.By means of time-division switching,the polarization of adjacent elements is orthogonal,so that the antenna array and RF front-end is miniaturized.Based on polarization sensitive characteristics,the estimation of DOA(Direction of Arrival)and polarization parameters of the interference signal are achieved by MUSIC algorithm.The PCMV(Polarized pattern Constrained Minimum Variance)is first proposed,by which the beam towards to signal and the null towards can be achieved in the same time when interference and signal come in the same direction.The simulation results show that the antenna element spacing can be reduced to 0.4 times of the wavelength while the isolation is larger than 27 dB,and the number of RF front-ends is reduced by half.When the signal and interference are in the same direction,the signal beamforming performance of PCMV is equivalent to MVDR(Minimum Variance Distortionless Response),while the interference suppression performance is better than MVDR and PI(Power Inversion).(4)In order to solve the problem of miniaturization of high power antenna in ground station of the control section,a power adaptive multi-beamforming technique based on distributed antenna array is proposed.The signal model of the distributed antenna array is established.The phase uncertainty and synthesis efficiency defined as evaluation indicators of the distributed antenna array are analyzed.By using the adaptive subarray and the improved BS criterion,the adaptive multi-beamforming of the small-aperture antenna is realized.The compatibility of multi-target tracking and single-target enhancing is achieved under the distributed antenna array multi-beamforming technology,while the capability of anti-interference and combat are also improved.Theoretical analysis and simulation show that the efficiency of distributed antenna array is 10% higher than that of traditional multi-beam antenna when the antenna array is scanned at an angle of 60 °.When synthesis efficiency is required to 75% in 80 ° wide angle range,the initial phase calibration accuracy factor and the relative positioning accuracy factor are required not to exceed 0.2.Finally,the research results of the paper and its application are summarized,and the work to be carried out in the next step is prospected.The research results of this paper can provide technical reference for the development of normal receivers and ground control system ground stations in Beidou satellite navigation systems in China.