Study On Approaches And Applications Of Interrupted Sampling Modulation On Wideband Radar Signals

The Development of the electronical devices makes it possible to flexibly modulate on the waveform,then waveform combat has worked as an important aspect for both the wideband imaging radar and the radar jamming system.For the jamming radar,the waveform with good anti-jamming potentials should be designed to obtain the target image under complex electromagnetism environment.For the jamming system,the flexible modulation on the intercepted radar signal should be adopted to obtain robust jamming performance.Hence it is of great significance to conduct studies on the issue of radar signal modulation.Interrupted modulation technique is widely applied in radar signal processing especially in imaging radar jamming due to its simple operation and flexible performance.In this paper,taking the interrupted sampling modulation as the main technique and the wideband imaging radar as the application,studies from the aspects of the theory system and actual applications are conducted for radar signal interrupted sampling modulation technique.The main contents are as follows:Firstly,the interrupted sampling modulation characteristics of radar signals are studied.On the basis of uniform interrupted modulation,the characteristics of coded interrupted sampling are analyzed in detail from the aspects of pseu-random coding and periodic cycling coding.Firstly,the characteristics of modulation pulse are analyzed.Then,the characteristics of radar signals after modulation are analyzed.Finally,the modulation results under different coding modes are simulated,and the influence of different modulation parameters on the modulation effect is given.This part of the work is the basis of this paper.Furthermore,an imaging method based on interrupted modulation signals is studied.A novel coded interrupted modulation LFM imaging signal is proposed by using the flexible time domain control characteristics of coded interrupted sampling modulation.Compared with the complete LFM signal from the perspective of time domain pulse stream density,signal spectrum,fuzzy function,matched filter characteristics,etc.,the proposed signal has the advantages of wide time-bandwidth product and high Doppler tolerance similar to LFM signal.Besides,the amount of imaging sample data can be greatly reduced and the anti-interference performance is better for the proposed signal.Secondly,for the problem of high range side lobes brought by the traditional pulse compression imaging processing,the segmentation sparse characteristic of the signal is used based on the theory of compressed sensing.The orthogonal matching pursuit(OMP)algorithm reconstructs the target image,and obtains the high-resolution image of the target.Finally,the effectiveness of the proposed method is verified by the simulation of the ISAR data and the microwave darkroom experiment.Subsequently,the target HRRP reconstruction method of full-polarization imaging radar based on orthogonally interrupted modulated signals is studied.Aiming at the strict orthogonality requirement of simultaneous full-polarization imaging radar for different polarization channel signals,the intra-pulse time domain diversity characteristic of interrupted sampling modulation is used to obtain the orthogonal modulation interlaced modulation of the complete signal.The ideal orthogonal full-polarization imaging signal is obtained in the intra-time domain;secondly,in order to make full use of the correlation between different polarization channels,Fully-Polarization simultaneous OMP(FP-SOMP)algorithm based on joint sparsity is proposed to reconstruct the target's HRRP,which effectively improves the probability and accuracy of HRRP reconstruction.Finally,through mathimatical simulation and measured full-polarization data experiment,the proposed method was validated and analyzed.Finally,the feature control method of imaging radar target image based on interrupted sampling modulation is studied.An active cancellation method for imaging radar based on interrupted sampling modulation is proposed.The method utilizes the unique characteristics of uniform and coded interrupted modulation,and solves the problem of the cancellation signal and the radar echo amplitude mismatch caused by non-ideal factors such as delay offset and phase estimation deviation.On the basis of cancellation,the residual image of the cancellation target is protected by the generated multiple realistic false targets or suppressed interference bands on the radar image,which effectively improves the robustness of echo cancellation;An ISAR target suppressed jamming method is proposed based on coded interrupted sampling modulation.The method forms a two-dimensional suppressed interference band extending along the range direction and the azimuth direction by performing joint coding interrupted sampling modulation on the intercepted radar signal,thereby effectively concealing the image features of the desired protection target.Compared with the traditional ISAR image feature control method,this method does not need to modulate the target scattering characteristic template,thus greatly improving the real-time reaction and the practical achievability of the modulation signal generation.