Analysis And Identification Of Radar Modulated Signal

Intra-pulse modulation recognition is the first and most important step of electronic countermeasures in the battle of radar.Through the analysis of the intermediate frequency of intercept the enemy radar signal,intra-pulse modulation recognition can obtain the corresponding modulation mode of the signal,providing guidance and basis for parameter estimation,pulse string sorting and subsequent radiation source recognition algorithm in the receiver.It enables our own radar system to obtain real-time information about the enemy radar,which guides our own combat system to counter enemy radar by electromagnetic deception,interference,suppression,control,even destruction to seize advantage in the battle of radar.This paper mainly studies the receiving signal preprocessing,signal modulation recognition algorithm and the reliability evaluation algorithm of modulation recognition in the radar modulation signal blind identification system,including the design of blind identification system,the separation of radar pulse sequence and compound modulation signal,the recognition of the non-phase modulation frequency modulation signal,the recognition of phase modulation frequency modulation signal and the reliability evaluation algorithm.Also the simulation and analysis of the performance of these algorithms is presented.The main contents are as follows:First,the preprocessing algorithm in radar modulation signal blind identification system is studied.The separation algorithm of radar pulse sequence based on grouping in time domain is studied,including the simulation analysis in different noise power,pulse repetition frequency and the separation performance of the pulse sequence under different threshold factors.The simulation results indicate that when the SNR(Signal to Noise,SNR)is greater than 6 dB,the separation probability can reach more than 90%.Also,the separation algorithm of multi-modulation signal in single pulse is studied,the simulation of which shows that when SNR is greater than-5dB,the separation probability can reach more than 90%.The blind estimation algorithm of signal bandwidth and carrier frequency is also studied.In sum,the process has good robustness when confronted with different signals and parameters,which lays a foundation for the subsequent modulation recognition algorithm.Secondly,this paper studies the discriminant algorithm between the non-phase modulation frequency modulation signal and the phase modulation frequency modulation signal.In the non-phase modulation frequency modulation signal,the signal of time-frequency distribution image recognition algorithm based on signal spectrum peaks protruding are studied.These two characteristics not only can distinguish the two signals,but also can serve for the identification of the phase modulation frequency modulation signal modulation mode.Simulation shows that when SNR is greater than-10 dB,the recognition rate of both algorithms can reach more than 90% in the recognition of radar conventional signals and single tone multi-modulation signals.In the separation algorithm of radar phase modulation frequency modulation signal,recognition algorithm based on wavelet transform and time-frequency image of discrete degree is studied.The performance of two algorithms can be obtained by the simulation under different number of element,which show that the algorithm based on the time-frequency image of discrete degree is superior to the former.It achieves the discrimination accuracy of 90% when the SNR is larger than-12 d B.After that,the identification algorithm of radar phase-modulation signal is studied.As for radar phase-modulation signal recognition algorithm,the phase modulation of FM radar signal recognition algorithm based on multiple parties of spectral lines and multiple phase difference are studied,and the simulation analysis of the performance under Additive White Gaussian Noise channel is presented.The simulation results indicate that the performance of the two algorithms decreases sharply after the number of codes is reduced,but the sensitivity of the algorithm based on multiple phase difference is stronger than that of the former.The recognition rate of the two algorithms can reach more than 90% when the number of codes is 64 and SNR is greater than-6dB.In the recognition of frequency modulation signal,the spectrum peak extraction algorithm based on phase matching are studied and the simulation analysis of the recognition performance under different parameters is presented.The simulation results show that when SNR is larger than 10 dB,the recognition performance of two algorithms can achieve more than 90%.Finally,the recognition performance of the measured and simulated signals in the radar modulation signal blind identification system is analyzed.The reliability evaluation algorithm based on linear regression to test loss is studied.Under the premise of the correction of the parameter estimation,the two hypothesis test questions are raised.The recognition reliability of radar conventional signals,BPSK signals and LFM signals at different SNR and confidence levels is simulated and analyzed.Simulation results show that the reliability of recognition of the three signals is greater than 90% when the confidence level is 0.01 and the SNR is-11 dB,-10 dB and-12 dB respectively.