A Study Of Multistatic Radar For Target Localization

In electronic warfare, it is a quite important task to quickly locate threat radiation targets with high precision, which is of great help to guide weapons to precisely destroy enemy platform to provide effective protection. There are a lot of methods of target positioning which includes active positioning and passive locating. As a traditional positioning method, active positioning radar can be easily destroyed in the war, thus making it difficult to survive and complete the task. Working in a passive way, passive radar does not emit signals, endowing it with good hiding and survival ability and many other outstanding features, which can make up for the deficiencies of active radar in battlefield. However, it can only locate targets with electromagnetic radiation. Besides, due to its lack of distance information of targets, its positioning accuracy is worse than active positioning normally speaking.This paper describes several conventional positioning methods which locate targets through three or more curved surfaces which can usually meet in the target position. The multi-station positioning methods realize locating by using the oblique distance information from target to each site. Passive positioning system includes angle of arrival location, time difference of arrival location and the combination of the two methods. AOA and TDOA measurements are divided into passive TDOA location positioning method combines with azimuth or with elevation angle.Firstly, basic principles of these location methods and the concept of geometric dilution of precision is introduced, as well as the corresponding theoretical derivation. The positioning ambiguity in positioning algorithm is analyzed and the way to solve this problem is presented. The positioning accuracy of Y-shaped layout and diamond-shaped layout is analyzed. The effect of different factors on GDOP is analyzed such as the precision of the time difference, the precision of angle, the distance between sites, site errors, target heights and so on by changing different factors.Secondly, methods to improve the locating precision are proposed. Due to the baseline is too small in vertical direction, the vertical GDOP is poor in low-altitude. To solve this problem, the elevation angle information in the master station is added. By increasing the number of receiving stations, additional subsystems can be obtained. When the extra data is used, it can not only eliminate locating ambiguity but also improve the GDOP effectively. A comparison of the positioning accuracy of three-station TDOA and two-station TDOA is made by simulation, the result of which confirms that increasing the number of observation station can lead to better positioning performance.Finally, the correction of site errors is discussed in detail. This paper proposes a self-localization method which uses the data of the target echo to correct site errors. The distance from sites to target and the distance among different sites are calculated. Then the differential distance can be obtained. With the use of linear minimum mean square error(LMMSE) the site errors can be estimated as well as the adjusted site position. With the new sites’ information a reposition can be made. This method can effectively increase the positioning accuracy of the target.