Research On Recognition And Parameters Accurate Estimation Of Polyphase-coded Radar Signals Under Asynchronous Conditions

In this paper, recognition and parameters accurate estimation of polyphase-coded radar signals, such as Frank code, P1 code, P2 code, P3 code, P4 code, under asynchronous conditions is researched.In general, the radar signals received by the radar-receiver are not synchronous, so the start time and the end time of them must be obtained at first. A rough estimation on the time of arrival and end of the received signals is taken with the help of correlation detection algorithm and then accurately estimated using Haar wavelet transform in the paper.On the base of having estimated the start time and the end time of the received signal, the code width of polyphase-coded signals is accurately estimated by Haar wavelet transform combined with modified Rife algorithm, on whose estimation accuracy the effect for signal asynchronization is discussed at the same time.According to the phase coding patterns of the ployphase-coded signals, the spectrum characteristics of the signal obtained by auto-correlation operation of them is analyzed, on which the effect for signal asynchronization is presented by lots of simulations and as a result, a new detection algorithm of polyphased-coded signal based on DFT under asynchronous conditions is proposed.In the end, on the base of the polyphase-coded signal that has beed detected, local base-band reference signals are constructed and then multiplied with the received signals. When one of the local base-band reference signals has the same modulation mode with the received signals, the result of the multiplication is a sinusoid. By this property together with the maximum likelihood rule, the polyphase-coded signals can be classified, whose carrier frequency can also be accurately obtained by estimating the frequency of the sinusoid using the modified Rife algorithm.The comprehensive simulation results shows that the recognition and parameters accurate estimation algorithm of the polyphase-coded radar signals under asynchronous conditions is correct and effective, having certain practical meaning.