Research On Intra-pulse Feature Analysis Methods Of Polyphase Codes Radar Signal

With the development of the information technology,great changes have taken place in the form of wars.The useage,interception,process and classification recognition of radar signal have become the focus of our research.Since,the forms of Radar signal being more and more complicated,especially phase code signal has been put into use in the modern radar widely,it can have great significance in the recognition research on phase code signal.This article focuses on the characteristics of radar polyphase code signal,and according to its time-frequency characteristics,the improved time-frequency intra-pulse feature analysis method is used to realize the characteristic analysis and parameter estimation of the signal.Finally,the recognition frame is built according to the phase characteristics of the multi-phase code radar signal to achieve more accurate identification of the signal.In view of the above,this paper has carried out the following work in depth:Firstly,several typical radar modulation signal models are constructed and characterized on time domain and frequency domain.Three traditional time-frequency analysis methods are analyzed and compared.In-depth study of the principles of these time-frequency analysis methods and their application in feature extraction.The architecture of the radar signal intra-feature analysis system is briefly introduced.Secondly,the phase difference of five kinds of polyphase code signals(Frank code,P1 code,P2 code,P3 code and P4 code)is derived.Since,the first-order phase difference curve of the signal is sensitive to noise,so,the processing effect of the heavy-phase differential pair signal is studied.The apparent hopping characteristics of the five phase polyphase codes have significant hopping characteristics.In this paper,the phase coded signals BPSK,QPSK and the polyphase code signals are identified by the number of hopping points,the hopping amplitude,and the position of the hopping points.The signal recognition framework is built and the identification process is designed.The experiment simulation verifies the feasibility of this method.Thirdly,a joint analysis method combining time-frequency analysis and image processing is proposed.The image processing method improves the noise immunity of the algorithm after processing the time-frequency map.From the aggregation of the time-frequency map after image processing and the mean square error curve of signal parameter estimation,it is verified that the detection performance of the multi-phase code signal can be greater than 90% under the condition of low SNR-5dB.At the same time,the method also has good parameter estimation performance.Finally,the fractional Fourier transform(FRFT)analysis method is deeply studied.In the fractional Fourier transform of polyphase code signals,the optimal order determination is the focus of the whole algorithm,and the order of FRFT has a certain relationship with the modulation frequency of the signal.In this paper,the quadratic phase function of two-component LFM signal is derived,and a joint method based on quadratic phase function and Radon transform is proposed.When the signal-to-noise ratio is lower than-4dB,the parameter estimation performance is significantly better than the traditional Radon-Wigner transform(RWT)method.