Study Of Real-time Spectrum Estimation Method Of Random Demodulation Based On FPGA

The traditional spectrum estimation requires Nyquist sampling of the signal first,which results in a large waste of resources and time.Random demodulation system is a kind of analog information conversion structure based on compressed sensing theory,which can compress and sample the multi-frequency signal with unknown carrier frequency,and can sample the signal at a rate lower than Nyquist frequency,and compress the signal at the same time to ensure the integrity of the signal 's information.In the field of spectrum perception,precision and real-time performance are often required.Therefore,this paper focuses on the random demodulation real-time spectrum estimation method based on FPGA.The main contents are as follows:1.Study the principle of random demodulation.The principles of compressed sensing,random demodulation and signal reconstruction algorithms are studied in depth,and the various stages of random demodulation are explained by mathematical method,and the specific functions of signal model,mixing frequency,low-pass filtering,uniform sampling and signal reconstruction in the random demodulation system are analyzed.The feasibility of spectrum estimation based on random demodulation is verified by simulation experiments,which provides reference for the realization of spectrum estimation based on hardware platform.2.Implementation of OMP algorithm based on FPGA.The real-time performance of the OMP algorithm based on simulation is not enough,so the real-time implementation of the OMP algorithm is designed based on FPGA.Based on the full study of random demodulation and OMP algorithm,combined with the method of gradual QR decomposition proposed in recent years,the OMP algorithm for random demodulation complex number based on FPGA is realized.3.Build a hardware based random demodulation spectrum estimation system.Combining the existing hardware platform as the front end of random demodulation for compression sampling and the FPGA based OMP algorithm as the signal processing back end,the hardware based random demodulation spectrum estimation is realized.The front-end of random demodulation compression sampling includes upper computer,Analog Discovery2,signal conditioning circuit and power supply.The upper computer sets signal parameters,Analog Discovery2 generates analog signal and m sequence,and the regulating circuit compressors and samples,and finally sends the observed value to FPGA for processing.4.The random demodulation spectrum estimation system is used for hardware experiments.The hardware random demodulation system was used to generate signals and pseudo-random sequences,and compressed sampling was conducted to generate actual data.Typical experiments were designed to verify and study the OMP module based on random demodulation.The OMP algorithm based on FPGA achieved a speed of 35.192?s,and the lowest SNR of spectrum recovery was 28.25 d B.In addition,the relationship between the recovery SNR and the number of points,frequency interval and fixed-point format is verified by hardware experiments.