Research On Interferometer Direction Finding System

In the modern complex battlefield environment, electronic warfare needs surveillance system to get enemy's parameter information and location information on the premise of hiding and protecting itself. Passive detection system can satisfy this demand, and it's effective distance is farther than active detection. Due to the high accuracy of direction finding and simple algorithm, interferometer direction finding(DF) technology is one of the passive detection system and plays a very important role. Interferometer DF technology is widely used in modern military technology.Interferometer DF technology is a method of seeking azimuth by measuring the phase difference between the respective baseline. And the radar emitter signal is received by baseline with a variety of environmental noise. when the signal-to-noise ratio(SNR) is small, the azimuth measurement error will be great.To solve the above problem, the frequency domain analysis interferometer DF method is studied in this thesis. The blurring phase is obtained by analyzing the signal spectrum received by the DF baseline for each channel. Then, the ambiguity is solved by the long and short baseline method. Finally, the phase angle is obtained by the least squares method.Firstly, the basic principle of interferometer DF is studied in this thesis. And this thesis gives unidimensional and two-dimensional linear interferometer DF method. The experiment result shows that this method has high accuracy at high SNR, but the measurement error will increase as the SNR decreases.Then, the four key technologies of solving phase are analyzed. And under different SNR conditions, simulate and make a comparison between time domain and frequency domain of the digital phase demodulation technology. Besides, simulate and make a comparison between long short baseline and statistical phase variance of defuzzification algorithm. The results showed that in the digital phase demodulation technology, the frequency domain phase demodulation is better in the phase difference measurement accuracy at low SNR than time domain; in the defuzzification algorithm, the measurement accuracy of two methods are the same, but the measurement efficiency of long and short baseline method is superior to that of statistical phase variance method.Finally, the frequency domain analysis interferometer DF method is studied in this thesis. And this thesis compares the frequency domain analysis interferometer DF method with the time domain analysis method of the one-dimensional linear interferometer at different SNR. The result shows that the ability to adapt to the change of SNR of frequency domain analysis is better than that of time domain analysis. At the same time this paper also studies another interferometer DF method, namely signal point long short baseline(SPLSB) method, and compare with the time domain analysis method of the one-dimensional linear interferometer. The simulation result shows that the time domain analysis method is better than long short baseline method in the ability of direction finding at low SNR.Frequency domain analysis method is a very practical method of interferometer DF. It has high accuracy, and the affect of SNR change is small. SPLSB takes advantage of the phase difference information,which provide a new approch for the interferometer direction finding.