Research On Waveform Design And Signal Processing Of Phase-Coded OFDM Radar

Traditional radar signal,of which the form is simple,and the performance of concealment and security is bad,is easily detected by the hostile forces,interfered by the noise and other disturbing signals.Phase-Code Orthogonal Frequency Division Multiplexing(PC-OFDM)radar signal,a combination of the advantages of phase-coded signal and the OFDM scheme,has received an extensive attention in recent years.In this Paper,a series of studies will be done focusing on the waveform design and signal processing methods of PC-OFDM radar signal.First of all,the ambiguity function of PC-OFDM radar single pulse is derived in detail to verify that PC-OFDM radar signal with a thumb-shaped ambiguity function,has both high range,and Doppler resolution,between which there is no coupling relationship.However,PC-OFDM radar signal is sensitive to the Doppler frequency shift accordingly,for which specialized algorithm is required for the estimation and compensation of the Doppler frequency offset.Secondly,based on the research of the properties of several constant chaotic mapping methods,an improved quantitative mapping rule is presented to get the poly-phase code sets with good orthogonal performance.The sub-carrier weighting methods and the phase-coded sets are considered both from the aspects of the Peak-to-Mean Envelope Power Ratio(PMEPR)and the Peak-to-Side-Lobe Ratio(PSLR)of the auto-correlation function comprehensively.And based on the iterative clipping method,PC-OFDM signal with PMEPR(27)2 to meet the radar transmitter demand and low auto-correlation side-lobe level is obtained,and a systematic PC-OFDM waveform design and optimization scheme is proposed consequently.Thirdly,a two-step pulse compression method based on Cyclic Prefix(CP)is analyzed.By adding CP between the PC-OFDM bits,the Inter-Symbol Interference(ISI)from the segment displacement of different bits is eliminated,while the results of the algorithm are equal to matching filter,with algorithm efficiency being improved.Then based on the correlation relationship between the sampling points due to CP,the maximum likelihood estimation of the Doppler frequency offset is obtained and further more is used to compensate the amplitude loss of the main-lobe of the High Resolution Range Profile(HRRP)effectively.Finally,a mixed genetic simulated annealing algorithm is used to obtain a pair of approximately complementary phase-coded sets with the fitness function defined based on the PSLR,Integral-Side-lobe Ratio(ISLR)of the sum of auto-correlation function and the PMEPR of the signal.By transmitting a pulse pair modulated by the complementary code sets,the side-lobe level of the HRRP is compressed with the side-lobe cancellation processing done to the echo pulse pair.