Research On Technology Of Shortwave/Ultrashortwave Emmiter Location

Passive location has the ability of covert detection,anti-interference and anti-detection,because the receiving station will not actively send signals.It plays a very important role in both war and civilian fields.Passive location is divided into two categories,positioning for emitter and positioning based on opportunity transmitters.This thesis studies target positioning methods based on ultra-short-wave opportunity transmitter and shortwave emitter.Firstly,based on the different passive positioning systems,this thesis studies angle-based cross positioning,time difference positioning,frequency difference positioning and joint multiple parameters positioning respectively.For the target within visual range,this thesis proposes a positioning method for ultra-short-wave opportunity transmitter utilizing multi-parameters jointly.Then this thesis introduces the positioning method of the shortwave emitter,and proposes the corresponding positioning methods for the shortwave emitter and multi-shortwave emitters beyond visual range.The main content of this thesis can be summarized as:1.Aiming at the problem of localization for the moving target within visual range,an ultra-short wave opportunity transmitter positioning algorithm with multi-parameters is proposed.The measurement parameters include azimuth,elevation angle,arrival of time and arrival of frequency.The algorithm is based on the two-stage weighted least squares?2SWLS?algorithm^[1]model proposed by Chan,and is improved on the basis of the 2SWLS model,and finally a closed solution of the target's position and velocity is obtained.In order to solve the problem that when the target is in the far field,the observation performance of the system decreases and the positioning error increases,a first-order Taylor expansion is performed on the basis of the weighted least squares solution to reduce the positioning error.Through simulation results,it is verified that compared with the existing methods,the positioning results of the proposed algorithm are more accurate and can reach CRLB.Finally,by comparing the floating-point operands required by the algorithm with the running time of the algorithm,it is proved that the method of this thesis requires less calculation.2.For the shortwave emitter beyond visual range,basing on the spherical earth model first,a positioning algorithm for a short-wave emitter using uniform circular arrays arrays was proposed.Through simulation results,it is proved that the algorithm for the location of beyond-the-horizon emitter is effective.Then,in order to improve the positioning accuracy,the algorithm is applied to a more accurate WGS-84 model.The simulation compares the algorithm proposed in this thesis with the maximum likelihood method and the cross-location algorithm based on the reference plane of the earth ellipsoid^[2].The simulation results show that the proposed algorithm has more accurate positioning solutions when signal-to-noise ratio is bigger than 5dB in the simulation scenario.3.As for multi-shortwave emitters beyond the horizon,a multi-target localization algorithm based on feature subspace decomposition and uniform circular arrays is proposed.Compared with multi-target cross-localization,this algorithm does not need to consider the problem of false point removal.The noisy received signal space is first decomposed into a noise subspace and a signal subspace.Then,the search area is divided into multiple grid points,and the array flow pattern of the grid points relative to the receiving station is calculated.It is determined whether the search grid point is the target position by determining whether the array grid pattern of the search grid point is orthogonal to the noise subspace.