Subtle Characteristics Of The Radar Signal Extraction Method

In modern electromagnetic environment, the high density, overlapping in time and frequency domain, complex modulation and changeable parameters of signals bring a lot of difficult in electronic reconnaissance. Conventional pulse parameters are unable to describe the nature of radar effectively and the subtle feature extraction of radar signal becomes more and more important. This paper studies subtle feature extraction methods of radar signal in the complex electromagnetic environment, including the following:Firstly, the signal environment of modern radar countermeasure is analyzed; features in such as time, frequency, space and modulation domain, extraction methods of these features and the importance of these features are introduced; modern electromagnetic environment is simulated based on radar signal features.Secondly, in view of feature extraction of frequency stability, two fast and accurate frequency methods are studied: 1) Frequency estimation methods based on the correction of FFT spectrum; 2) Frequency estimation methods based on phase difference. One frequency estimation method using phase difference based on unwrap is given and the method reduces the SNR threshold of signal which has large absolute normalized frequency. In order to provide accurate Doppler frequency in radar position estimation, the CRB and method of frequency estimation of coherent signals are studied, the ULP method using coherent improves the accuracy of estimates of the frequency.At last, intrapulse features extraction methods of radar signal are studied; the application of scope, advantages and disadvantages of some methods of intrapulse features extraction are summarized. DCT is used to extract intrapulse features based on the fact that different types of signals in the modulation are related with different shapes of spectrum. One method which is base on instantaneous frequency can achieve modulation parameters of pulse. Because this method can recognize constant signal firstly, the computation of this method is small. In the analysis of several intrapulse features methods, an integrated intrapulse analysis method for complex electromagnetic environment is given.