Improved Time Frequency Distribution And Its Application In Radar Signal Process

In order to improve the performances of the analysis for radar signals, lots of methods based on the time-frequency distribution are introduced in the research of radar signals. Nevertheless, because the 2-D calculations of signals are required in the analysis procedure based on the time-frequency distribution, the enormous calculations become a main fact that confines the analysis efficiency of radar signals. It has become of an urgent problem that how to reduce the calculations in the signal process and keep the performances of the time-frequency distribution at the same time. In the researches of direction-of-arrival(DOA) of the radar signal, the spatial spectrum estimation based on the array signal process is a usual and pervasive method. There are many complex matrix calculations in the DOA estimation method based on the spatial spectrum estimation, therefore the large-scale calculations and the complicated procedures have influence the real-time efficiency of the DOA estimation of radar signals. It is a important task in the analysis of radar signals that to find a effective and rapid way to estimate the DOA of nonstationary signals.To improve the efficiency of the analysis for radar signals, this paper has began with the short-time signal and researched the Cohen's Time-Frequency Distributions and their applications in the signal process area. There are three aspects in the main research work.(1) The distribution properties of short-time signals in the time-lag domain are analyzed and summarized by theoretic and experimental methods. According to the conditions of suppression of cross terms in Cohen's time-frequency distributions, we propose the constraint conditions of suppression of cross terms in the time-frequency distribution for short-time signals.(2) According to the proposed conditions for the time-frequency distribution of short-time signals, we have analyzed and improved some types of Cohen's time-frequency distributions for the short-time signal. Moreover, we proposed the concept of the Cohen's time-frequency distributions based on short-time signals. According to the properties of short-time signals in the time-lag domain, we have proposed the definition of short-time compare distribution(SCD) and it's core function.(3) Using the improved time-frequency distributions based on short-time signals, we have proposed the application methods be used for the signal instantaneous frequency estimation, frequency modulation analysis and signal type recognition. On this condition, the procedures and algorithms of realization are proposed based on some types of improved time-frequency distributions. Corresponding experiments are conducted and analyzed.The theoretic analysis and experimental results show, in the analysis procedure...