Research On Direction Finding And Location Algorithms For Wideb And Signal

With the continuous development of electronic technology, the signal transmitted by modern radar is usually wideband modulated. Therefore, the research on the direction finding(DF) and localization algorithm for wideband signals is a subject with realistic significance. In this paper, several key operations and techniques are studied, such as high precision direction finding algorithm for single signal, algorithms of number estimation and direction finding for multiple coherent radiation sources under the background of decoys, direction finding for wideband interference sources, dual-station direction finding cross localization algorithm, FPGA implementation of wideband direction finding algorithm, and so on. Major innovative achievements are as follows:Firstly, based on high precision time delay estimation algorithm, long baseline direction finding algorithm was studied systematically. Direction finding algorithm for wideband signal based on time delay correction and unwrapping phase ambiguity algorithm were presented. Their performances and using conditions were discussed in detail. In the algorithm, the phase of the signal was corrected by the initial estimation of time delay. Then, the residual phase difference was estimated and phase ambiguity was unwrapped by the phase interferometer algorithm. The baseline length was not limited by the requirement of unwrapping phase ambiguity.Secondly, algorithms of number estimation and direction finding for multiple coherent radiation sources under the background of decoys were presented. For the multiple coherent radiation sources whose locations were close to each other, the radiation sources number could be estimated according to the spectrum architectural feature of signals by the single baseline composed of the two antennas. And the directions of multiple radiation sources could be found accurately. It had the certain application value in the electronic reconnaissance and intelligence intercepts. It also had the reference value in continue in-depth study on direction finding and localization.Thirdly, direction finding algorithms for wideband interference sources were presented. Before direction finding of interference source, the signal needed to be detected. For the derection finding of multiple interference sources, the MUSIC algorithm of array signal processing was used. Otherwise, the radar signal and interference signal might exist in the reality electromagnetic environment. So it was important to have the research on the detection and direction finding algorithm for mixed signals. The signals could be detected and recognized according to the maximum values and mean square values of spectral modulus after the short time Fourier transform(STFT) in the frequency domain. Then the directions were found by the interception of the useful data segments.Fourthly, based on high precision direction of arrival(DOA), dual-station direction finding cross localization algorithm was adopted. The location of the radiation source could be calculated by building angle observation equations. Then, location error of dual-station direction finding cross localization algorithm was analyzed. And how to obtain the highest positioning accuracy was discussed.Fifthly, the FPGA implementation of direction finding algorithm for wideband signal was discussed. In the channelized system of polyphase filters, time resolution of the data was lower after the extraction and the time-delay precisions of traditional time-of-arrival estimation algorithms were worse. In the direction finding algorithm of wideband signal, time-delay estimation was converted into frequency estimation according to the relationship between time domain and frequency domain. The precision of this algorithm was not limited by sample interval. This algorithm was simple and suitable for hardware implementation. And it could be carried out in real time processing and achieve very high precision of direction finding.Finally, the research on the algorithm of signal sorting and reference frequency estimation based on frequency agility radar was done. In this algorithm, the frequency of received signals was estimated in high precision firstly. The frequency difference was made between two adjacent signals. Then, the results could be got by the division between the two adjacent frequency differences. Within a certain range, the signals from different radars were sorted by comparing the fractional part of the results. According to the signals from the same radar, reference frequency could be gained. It could restrain the error sorting in the signal sorting and recognize the specific emitters accurately.