The Technology Of NLOS Passive Location Of TDOA For Remote Target Base On Satellite And Ground Station

In modern electronic information combat system,passive location system is always an important part of electronic reconnaissance.Although space technology and spaceborne reconnaissance technology have developed rapidly in recent years,the inherent defects of space-based and ground-based reconnaissance and positioning systems still bring many problems to electronic reconnaissance and positioning.Therefore,based on the multi-satellite monitoring platform,it is considered to introduce the ground-based monitoring and positioning node,so as to improve the information coordination and comprehensive application ability of the space-based and ground-based positioning system and realize the accurate positioning of the satellite and ground monitoring platform.In this paper to solve the core problem is: aiming at the positioning mechanism of TDOA,how to break through the strict restriction of the direct vision condition when the target is located by the ground station reconnaissance and positioning system,and realize the introduction of ground-based reconnaissance system to satellite monitoring platform,so that the space-based reconnaissance and positioning system can achieve more reliable and accurate positioning effect.In this paper,the radio propagation modes of ultra-short wave and microwave electromagnetic wave which are widely used today are studied in depth,and it is found that they realize long-distance non-line-of-sight transmission between ground transceiver stations by using troposcatter scattering mechanism.Therefore,this paper analyzes the physical principle of tropospheric scattering communication,and makes clear that the propagation mode of electromagnetic wave in the troposphere is "refraction--scattering--refraction".On this basis,according to the characteristics of troposphere atmosphere,the concept of equivalent earth radius is introduced in this paper to offset the bending effect of propagation path caused by refraction,so as to facilitate geometric modeling.Combined with the existing scattering propagation models,the geometric model of the tropospheric scattering propagation path is established in this paper when the scattering points are located at different positions under the equivalent earth radius model,and then the calculation formula of the scattering propagation delay is given.Next,the characteristics of troposcatter transmission channel are studied in this paper,and it is determined that troposcatter is a random multipath channel,besides,the empirical formula of signal transmission loss is given.In order to study the influence of multipath on the delay of propagation path,the main factors affecting the delay of propagation path,namely,the scattering point height and the scattering angle,are analyzed by using the formula of scattering delay,and it is found that the influence of the two factors on the delay of propagation path is negligible.Therefore,a transmission model based on the equivalent earth radius model is constructed based on the transmission path trajectory of the lowest scattering point.And at the same time,in order to facilitate the comparison,the linear transmission model and the transmission model ignoring refraction factors are constructed.In addition,this paper presents the simulation method of satellite and ground station receiving signals and the estimation method of TDOA.Finally,based on the different components of the positioning platform in the satellite and earth joint positioning system,it is divided into two satellites and one ground station positioning system and one satellites and two ground station positioning system.Combining three kinds of channel models,the TDOA positioning equations of different satellite and ground joint positioning systems are constructed,and the Newtonian analytical algorithm is given.Then,this paper uses STK to select the location of satellite platform,ground monitoring station,target station and ground calibration station.Based on these location informations,simulation analysis is carried out on the effects of two positioning models and three transmission models on the positioning accuracy of different SNR and the positioning effect of the three models under the condition of relatively low SNR.The results show that,firstly,the positioning error decreases first and then becomes stable with the increase of SNR;secondly,the equivalent earth radius transmission model proposed in this paper is the closest to the actual transmission path length,with small positioning error and stable positioning effect.Therefore,this paper realizes the accurate location of TDOA for remote targets with non-line-of-sight based on satellite and ground station.