Research On Key Technologies Of Radar Systems Based On Wideband Waveform

Wideband high-resolution radars have been widely applied and play an important role in the modern military field.Wideband transmitting waveforms have unique advantages in radar system applications.For example,more detailed structural information about target can be obtained by processing the wideband radar echoes compared with narrowband waveforms.In addition,by transmitting wideband or ultra-wideband signals,wideband radars have the advantages of lower clutter backscattered power,lower target echo fluctuation,lower probability of interception,higher accuracy of parameter estimation,better anti-jamming and better electromagnetic compatibility,etc.However,there are many problems and difficulties in the applications of wideband radar.How to effectively deal with and solve the problems and difficulties in the wideband radar applications,and fully explore the potential of the wideband radar is of great significance for the development of radar technology.In this dissertation,some key technologies in the applications of wideband radar system have been studied in depth,and corresponding algorithms are proposed to solve the problems and difficulties in the applications.The main contributions and innovations are as follows1.The micro-Doppler ambiguity problem in wideband radar applications has been studied,and a flexible ambiguity resolution algorithm based on time delayed cross-correlation processing has been proposed in this dissertation.Wideband radars usually work on a high carrier frequency and low pulse repetition frequency has been often used in long-range wideband radar applications.These factors may cause serious micro-Doppler frequency ambiguities when the target has micromotions.By applying the algorithm proposed in this dissertation,we can obtain variable sizes of micro-Doppler shrinkage ratios.Under different degrees of ambiguity,the micro-Doppler ambiguities can be resolved and appropriate size of micro-Doppler frequency results can be obtained2.The problem of high-precision range estimation for range-spread targets has been studied,and a method based on the phase of wideband radar echoes has been proposed in this dissertation,which is not restricted by the phase ambiguity resolution constraints.Higher carrier frequency and lower pulse repetition frequency in wideband radar applications will cause serious phase ambiguities.Therefore,how to achieve the correct phase unwrapping results without ambiguity is the key to obtain high-precision target range estimation results.By applying the method proposed in this dissertation,the phase changing rate of the target echoes in the slow-time dimension can be greatly reduced.The real values of the phase difference after processing can meet the requirements of correct phase unwrapping,thus the phase unwrapping results without ambiguity can be obtained,as well as the high-precision range estimation results.3.The problem of angle estimation for range-spread targets has been studied,and a high-precision angle estimation method for wideband radar based on phase comparison monopulse and phase-difference ambiguity resolution has been proposed in this dissertation.In the wideband radar applications,the traditional narrowband angle estimation methods are not suitable for wideband transmitting waveforms because the target extends in the radar radial range dimension.The method proposed in this dissertation uses the phase-difference extraction of dual-antenna echo signals backscattered from a range-spread target,and takes advantage of the frequency estimation result to resolve the phase-difference ambiguities,so as to obtain the non-ambiguous phase-difference,and then the high-precision target angle estimation results can be achieved.4.The problems and difficulties in range-spread target detection have been studied,and a range-spread target detector based on two-dimensional scattering distribution features of the target has been proposed in this dissertation.This detector takes advantage of several echo pulses to compute the likelihood function to obtain the two-dimensional distribution characteristic matrix from two consecutive pulse trains,and uses the maximal normalized cross-correlation coefficient between the two matrices to construct the range-spread target detector.This detector is insensitive to the aspect change of target,and can be applied to high-speed and fast-rotating maneuvering targets.