Characteristic Analysis And Parameter Estimation Of LPI Radar Signals

In modern electronic warfare,the low probability of interception(LPI)radar,which has been widely used in recent years,has effectively improved the battlefield survivability of the radar by adopting a series of technical means such as complex modulation signals with large bandwidth and large bandwidth.Electronic reconnaissance receivers need to intercept signals from enemy sources in complex electromagnetic environments without priori information.Electronic reconnaissance receiver needs to intercept the signal of enemy radiation source in the complex electromagnetic environment without prior information,and carry out characteristic analysis,detection and identification and parameter estimation for it,so as to provide a basis for the subsequent countermeasures such as electronic interference and attack.Hence the application of LPI radar has great difficulties in the field of electronic reconnaissance of non-partners,it is of great practical significance to study the theory of LPI radar reconnaissance signal processing.On the basis of summarizing previous work,this paper studies the analysis and processing of typical LPI radar signals.The main contents are as follows:This paper firstly analyzes the factors affecting the probability of radar interception from the definition of LPI radar and interception factor,and summarizes the characteristics of LPI radar and the technical means to improve the low intercept performance of radar.Then several classic LPI radar signals are introduced,including chirp signals,phase-encoded signals,frequency-encoded signals,and composite modulated signals.After the signal model is established,the characteristics of these LPI radar signals are analyzed by its time domain waveform and spectrum.Several typical time-frequency analysis methods such as short-time Fourier transform,Wigner-Wille distribution and wavelet transform are studied.The characteristics of these methods are analyzed by simulation experiments on LPI radar signals.Since the Wigner-Wille distribution has cross-term interference effects,the improved Wigner-Wille distribution is introduced.This method reduces the complexity and computational complexity of the signal recognition algorithm and improves the noise immunity.Secondly,the parameter estimation algorithm of typical LPI radar signals is studied.The parameter estimation algorithm of fractional Fourier transform based on interpolation compensation optimization is studied due to the good energy clustering of the chirped Fourier transform.According to the cyclostationary feature of the coding-like signals,the parameter estimation algorithm based on cyclic spectrum correlation is studied.Aiming at the parameter estimation of composite modulated signals,based on signal reconstruction and filtering preprocessing,the parameter estimation algorithm using interpolation and fractional Fourier transform and cyclic spectrum correlation is studied.Finally,aiming at the extraction of intra-pulse features such as instantaneous amplitude,phase and frequency of radar signals,the coordinate rotation digital computer(CORDIC)algorithm is studied.An iterative algorithm for extracting the intrapulse features of a signal using the vector mode of the circular CORDIC algorithm is introduced.The flow-like iterative structure of the CORDIC algorithm is used to extract the instantaneous amplitude and phase of the signal,and then the instantaneous phase difference is used to extract the instantaneous frequency of the signal.Analysis and resolution of phase winding,clock and register configuration and data format issues.The Verilog language is used to complete the circuit description and completes the compilation and simulation verification.