Research On Three-Satellite Passive Tdoa Location Algorithm

Using satellites to scout targets on the ground and at sea is very important to improve the military force of one country, and obtains more and more attention. At the area of earth observation, how to locate the target at the environment of strong interference and noise plays a pivotal role at this area. Compared to the active location, the passive location is more elusive and the detection range is farther. This way locates and identifies target to the max accuracy at the condition of hiding one's own side. This thesis researches on three satellites Time Difference of Arrival location algorithm at the area of passive location.Firstly, this thesis builds block design for time-delay location system, and researches on the generalized correlation method to estimate time-delay. In allusion to seeking characteristic of generalized correlation method, this thesis proposes a method to seek the symmetry axis, and this method can improve the accuracy of estimation. Then the time-delay estimation experiment is made at the conditon of different time-delay and differnernt SNR with generalized correlation method, and the results show that the way to seek the symmetry axis has good performance.Then, on the base of analysis to generalized correlation method, this thesis researches on the Doppler Effect to time-delay estimation, and builds mathematical modeling for Doppler Effect. Considered to the compression of time domain of Doppler Effect, this thesis introduces fractional Fourier transform. It converts the signals to the similar scale domain, and then estimates the time delay. From the experiments at the condition of different Doppler speed with these two methods, we can see that FrFT could improve the anti-Doppler Effect ability.At last, this thesis builds the model and simulates the three-satellite location system. The system contains determination of coverage area, simulation of received signals, and simulation of time-delay estimation, and solver of location equations. On the base of the theoretical research and simulation design, this thesis analyzes the location accuracy, which mainly contains the influence caused by time-delay estimation and satellite location estimation error, and distribution of three satellites.From theoretical analysis and simulation experiment,at results, the time-delay estimation method based on FrFT has good anti-Doppler Effect performance, and provides parameter basis for three satellites Time Difference of Arrival location.