Research On New Wideband Digital Receiver Based On MWC Compressed Sampling Structure

Wideband digital receiver is widely applied in the electronic reconnaissance system in order to intercept the hostile radar signal,to recognize the signal modulation type and to obtain the pulse description words.Based on these parameters,strategic support can be provided to our own side.Nowadays,there are some bottleneck problems that contain more and more complex structure,larger and larger amounts of samples and the difficulty of cross-channel signal processing with wider and wider bandwidth design and the increase of channelization number in the conventional wideband digital receiver based on the uniform channelization design.The compressed sampling(CS)theory can help to intercept signal by a small quantity of CS data based on the signal sparsity of the electronic reconnaissance environment.In this paper,the modulated wideband converter(MWC)based on CS is extended to digital domain in order to construct a brand-new wideband digital receiver.By using this structure,less branches compared with uniform channelization reiciver are required and sub-Nyquist sampling rate can be obtained.Since all spectrum information of the received signal can be mixed to the baseband,it is beneficial to solve cross-channel signal problem.Since the random mixing based on MWC causes the true frequency and phase information of the CS data to lose,then how to obtain the technical parameters of the original signal by directly processing the CS data without reconstruction would be the key problem that needs to be solved for the proposed new receiver.The main research contents and the innovations of this paper are shown as follows:Firstly,an energy detection method based on the CS data is studied in order to detect and intercept unknown signal in the electronic reconnaissance environment.The CS signal detection model based on MWC is established and the criterion of the energy detection based on the CS data is formulated.Then,the signal detection and the pulse interception are completed by using the energy statistics of the CS data to carry out single point detection.Furthermore,an energy detection method based on the hybrid superposed energy statistics of the multi-branch CS data is proposed so as to achieve better signal detection performance under low signal-to-noise ratios(SNR).Secondly,an intra-pulse modulation recognition method based on the short-time Fourier transform(STFT)and the spectrum energy focusing rate test is studied in order to obtain the intra-pulse modulation type of the received signal by processing the CS data.The STFT spectrum bandwidth is tested to distinguish phase modulation signal and frequency modulation signal roughly.Then,the spectrum energy focusing rate of the CS data is tested to recognize the intra-pulse modulation type specifically.Moreover,another intra-pulse modulation recognition method based on the multi-branch hybrid superposed CS data with phase correction is proposed in this paper,which could increase the intra-pulse modulation recognition rates under low SNRs significantly.Finally,a uniform linear array(ULA)based MWC discrete compressed sampling structure is proposed to complete the carrier frequency(CF)and direction-of-arrival(DOA)estimation.In order to solve the problem that the random mixing causes the array CS data to lose the true frequency and phase differences,this paper proposes to use the cyclic-shifted pseudo-random sequences to complete the mixing operation so as to get the estimation of the sub-band index where the original signal exists.Then,the orginal CF can be recombined.Besides,the phase differences of the array CS data can be corrected.Finally,high-resolution MUSIC algorithm can be used to get the DOA estimation.Furthermore,aiming at the problem that the phase compensation fails under low SNRs,a modified ULA based system is proposed to achieve better DOA estimation performance and keep the same CF estimation performance in the case of low SNRs.