Research On Time-Frequency Interferometer Direction Finding Algorithm

Direction finding becomes a key technique in current electronic reconnaissance which works in complex environment with extremely dense signals.Whereas traditional phase interferometer as one of the direction finding methods had to work with frequency measurement device to get DOA of signal and can only adapt to estimate direction of arrival (DOA) of a single pulse. It does not have the ability to estimate the DOA of LFM signals nor resolve multiple signals. So this paper is the algorithm research of joint estimation of DOA and frequency of typical radar signal utilizing narrowband receiver.Firstly, the paper starts with elaboration on basic theory of finding direction by the method of interferometry, such as the construction of interferometer direction finding system, the basal principle. Also, the paper analyze the measurement accuracy and the problem of phase ambiguity in interferometer direction finding in detail. This part is the foundation of later research.Second , the paper presents the model of narrowband intermediate frequency digital receiver and give the design of parameters. In terms of single frequency pulse signal, the article study the algorithms of phase interferometer and correlative spectrum interferometer (CPI), the focus is on the CPI's Joint estimation of frequency and DOA and solution of two-signals, then utilize the narrowband receiver the article gives the performance simulation and comparison of two methods.Then, the paper researches on the algorithm and performance of time-frequency interferometer for joint estimation of time-frequency and DOA based on cross Wigner-Ville distribution (XWVD). Moreover, sets up an arrangement of symmetrical arrays which are adopted to solve phase ambiguity.And achieves an enhancement of time-frequency distribution. through arithmetic average of the XWVDs of the multiple symmetric sensors. The computer simulation compare the performance of three interferometer direction finding methods in terms of single frequency signal. In addition, the paper discusses and analyzes the performance of time-frequency interferometer in terms of LFM signal utilizing narrowband receiver. Simulation results reveal that time-frequency interferometer can reflect more characteristics of signal and is real because the sensors needed are few and the computations are easier relatively.