Research On Channelized Receiving Technology Based On Fractional Fourier Transform

Channelized receiving technology belongs to the field of radar reconnaissance and has very important strategic significance in modern electronic countermeasures.It is a important research topic to find a way that can separate and detect the received signal,and then estimate the parameters of the valuable signal quickly and accurately.Based on basic theory on channelized receiving technology and channelized receiving methods widely used,combined Fractional Fourier Transform(FrFT),a channelized receiving method based on Short-time Fractional Fourier Transform(STFrFT)is proposed,and the signal parameters estimation method based on STFrFT is studied.The main content of this thesis contains the following sections: The related theories involved in channelized receiving technology are studied in the first part.Firstly,the basic theory of signal sampling is studied,including Nyquist sampling theorem,band-pass sampling theorem,digital down-conversion and channelization filter bank.According to the decimation and design theory of the filter bank,the channelized receiving method based on polyphase filtering structure is derived.Secondly,according to the correspondence between FFT and filter bank,the channelized receiving method based on STFT is derived.Finally,the channelization method based on polyphase filter structure and the channelization method based on STFT structure are simulated and verified.Experiments show that the two methods have the ability to realize separate reception and parameter estimation for radar signals existing in the monitoring frequency band.Signal processing theories based on FrFT and the method to realize channelized receiving based on STFrFT are studied in the second part.Firstly,the definition and nature of FrFT in signal processing field and the fast discrete algorithm are studied.Secondly,the STFrFT channelization structure is studied,and several important issues involved in STFrFT channelized receiving method are analyzed,including the selection of short-time window function and the order of FrFT.Then the channelized receiving method based on STFrFT is submitted,and the channel division method is derived according to the fractional-order domain sampling theorem of the signal.Finally,the channelized receiving method based on STFrFT is simulated,Experiments show that the method is able to detect the signals separately,and has a better performance than the STFT channelized receiving method when the parameters are reasonable set.The parameters estimation method based on STFrFT output results is studied in the third part.Firstly,the decision when the output cross multiple channels and the detection threshold setting method are studied.Secondly,the parameter estimation method is classified according to the form of received signal,and the parameters estimation method based on STFrFT and least squares,and the method based on STFrFT and Hough transform are studied.The situation of different types of signals arriving at the same time is analyzed.Finally,simulation results verify that the channelization method based on STFrFT has good detection and estimation ability for signal time-frequency parameters.