Design And Analysis Of Radio Frequency Random Demodulation System

Random demodulation(RD)system is an important method of applying compressed sensing theory to analog information conversion.It has the characteristics of simple structure and strong hardware implementability.To a certain extent,it can realize the compression observation of sparse analog signals,which has important practical significance for the application of compressed sensing theory to practice.However,there are many technical problems in the implementation of its radio frequency(RF)hardware system,such as the distortion of the mixing function,the non-ideal characteristics of the RF mixer and the influence of the non-ideal filter,and other non-ideal factors.These non-ideal factors have a great impact on the sampling and reconstruction of sparse analog signals,and even the original signals cannot be reconstructed.Based on the research of this research group,this paper designs a RF random demodulation system to realize under-Nyquist sampling of sparse multi-frequency signals in the frequency domain and sparse pulse sequences in the time domain.The effects of non-ideal factors in the compression sampling process of the RF random demodulation system are analyzed and corresponding solutions are given to verify the compression sampling capability of the random demodulation system in the RF band.The specific research contents are as follows:1.The compressive sensing theory and the basic principle of the random demodulation system are deeply researched.The sampling theory of the random demodulation system of sparse multi-frequency signals in the frequency domain and sparse pulse sequences in the time domain is analyzed in depth,and its sampling process and reconstruction method are described in detail through mathematical models,which are proved in theory The random demodulation system can compress and sample the sparse signal.2.An experimental platform of RF random demodulation system is designed.According to the signal model index to be verified,the design of the RF random demodulation system experiment platform is completed,including hardware design and software design.Among them,the hardware design includes the design of the measured signal and mixing sequence generation module,RF signal conditioning module and sampling module.3.Analyze the influence of non-ideal factors in the RF random demodulation system and give the corresponding solutions.Purchase microwave devices according to the hardware design of the system.Through the mathematical model of the microwave device,specifically analyze the impact of non-ideal factors in the system on the reconstruction effect of multi-frequency signals and pulse sequences.Finally,a general calibration framework for random demodulation system is given.The calibration method framework was used to calibrate the sensing matrix of the random demodulation system of multi-frequency signals and the random demodulation system of the pulse sequence,respectively.4.Design simulation experiments based on mathematical models of non-ideal factors in the system.It focuses on analyzing the influence of the standing wave ratio,isolation,frequency conversion attenuation,non-ideal filter and mixing sequence distortion of the mixer on the reconstruction results of multi-frequency signal and pulse sequence.Through simulation experiments,compression sampling of multi-frequency signals and pulse sequences with a Nyquist frequency not exceeding 2 GHz at a sampling rate of 100 MSa/s is achieved.The influence of the non-ideal factors in the system on the RF random demodulation system and the effectiveness of the corresponding calibration method are verified.