| In modern battlefield,the density of radar signal is very high,the bandwidth,carrier frequency and intra-pulse modulation type of signal is changeable.The electronic reconnaissance receiver needs to recognize its intra-pulse modulation type according to the slight difference between signals to determine the radar properties accurately,and to achieve effective interference.Faced with such a complex electromagnetic environment,the new generation radar signal reconnaissance receiver requires large instantaneous bandwidth,high sensitivity and the ability to process multiple different modulation types of radar signal simultaneously.The digital channelized receiver researched in this paper,which is the most widely used radar signal reconnaissance receiver,can not only better meet the above requirements,but also achieve full probability interception within the monitoring bandwidth.A multi-level wideband digital channelized receiver is designed in this paper,which solves the problem of low signal-to-noise ratio and low accuracy of modulation type recognition.First of all,in this paper,a two-level digital channelized high-efficiency structure is designed to enhance the signal-to-noise ratio of about 17 dB and obtain two kinds of frequency resolutions.This improves the limitations of single-channel channelized receivers in dealing with signals with different bandwidth characteristics.Secondly,the receiver uses the amplitude autocorrelation accumulation technique and channelized adaptive threshold to overcome the difficulty of signal detection in low SNR environment.Finally,this paper combines the multi-level channelization structure and the phase-accumulating transient autocorrelation technique to reduce the influence of noise on the phase,which solves the problem of low correctness of phase identification in the case of low SNR.In this paper,a multi-level digital channelized receiver with instantaneous coverage bandwidth of 500 MHz and capable of processing both cross-channel signals and simultaneous arrival signals is designed and realized based on FPGA.Simulation and test results show that the receiver can adapt to the low SNR environment of-6dB,and identify six different modulation types of radar signal with an average recognition accuracy rate of 90% or more in the laboratory environment. |
