Design Of Sub-Nyquist Sampling System For Sparse Signal In Frequency Domain Based On MWC

With the rapid development of communication technology,the carrier frequency of radio frequency transmission is getting higher.Since the carrier frequency changes with time in the areas of cognitive radio,electronic reconnaissance etc,it is impossible to obtain the information by sampling the modulated wideband signal,which calls for the information to be acquired through sampling the wideband signal directly.If the traditional sampling method that follows Nyquist theory is adopted,it is difficult for the commercial analogto-digital converter to meet the requirements.In recent years,the Modulated Wideband Converter(MWC)sampling method proposed for the sparse signal in the frequency domain can reconstruct the original signal at a sampling rate that much lower than the Nyquist rate and reduce the sampling rate of the system.At the same time,the method also alleviates the storage and transmission pressure which caused by a large amount of data.But MWC sampling system is still in the theoretical analysis and simulation stage,which still has many problems to realize MWC sampling system.So this article has carried out the following work for the realization of the MWC sampling system:Firstly,the frequency domain sparse signal model for MWC system is analyzed.Then the structure of the sampling system is studied and theoretical analysis in the frequency domain is made.Finally,simulation experiment to verify MWC theory is designed.MWC sampling system is designed.The realization of MWC system technology is studied deeply,the existing components is used to design and implement a complete set of MWC system that consists of upper computer and lower computer.The lower computer takes FPGA,multiplier,AD sampling device and USB controller as its core and includes the input signal preprocessing circuit,pseudo random sequence generator,random mixer,low pass filter,synchronous low speed sampler and data transmission circuit etc.The upper computer realizes the reconstruction algorithm based on Orthogonal Matching Pursuit by MATLAB software and compiles the application that can realize the function of parameter setting,automatic calibration and real-time display of reconstruction results.Automatic calibration system is realized.Aiming at the problem that the actual value of sampling matrix does not accord with the theoretical value,which affects the reconstructed result,an automatic calibration system of MWC sampling matrix based on the sine response method is designed and implemented.The system uses program-controlled commands to generate a certain frequency,which can traverse the sinusoidal signal excitation source of the entire frequency band and obtain the sampling matrix data corresponding to the frequency.Experimental results show that the sampling matrix obtained by the MWC automatic calibration system can reconstruct the original signal with high probability.The entire system test is completed.The hardware circuit and the function of each module is tested,then the function of whole system is verified.The test results show that this system can reconstruct multi-band sparse signal with onetwentieth of the Nyquist rate and the success rate of single-band signal reconstruction is up to 98.5%.