Research On Radio Frequency Spectrum Compressed Sensing System Using Multimode Fiber

With the rapid development of information technology,the field of national defense is facing a complex and changeable battlefield environment.The wide spectrum,broadband,and nonlinear electronic battlefield has brought new challenges to traditional broadband spectrum sensing equipment.The analog-to-digital converter is limited by the sampling theorem,so a higher sampling rate is required,and the massive amount of data generated will also increase the pressure on the back-end processing capabilities.Based on the theory of compressed sensing,it is possible to sample and reconstruct the sparse signal at a rate lower than the Nyquist rate,thus alleviating the above-mentioned pressure.Microwave photonics has the characteristics of large instantaneous bandwidth,strong stability,and anti-electromagnetic interference.After complementary advantages,the photon-assisted compressed sensing technology has been produced.This technology has also become a subject of strategic research significance.In order to solve the problems of high complexity,poor real-time performance,difficulty in integration and high cost of existing systems,this paper uses complex mapping from space to frequency when optical pulses are transmitted in multimode fiber to randomly encode the spectrum.Based on the theory of frequency-time mapping,Using photon time-domain stretching technology is equivalent to realize the time-domain random modulation of light pulses.This method has the advantages of passive random coding,large bandwidth and low cost.After the signal to be measured is modulated,the dispersion broadens further produces time-domain superposition,and the integral operation on the light is completed.The single-channel structure simplifies the system,allowing a single measurement to quickly acquire data for reconstruction.The main research results and innovations of this paper are as follows:(1)Analyze the principle of the system,abstract the mathematical model,and demonstrate the feasibility of the scheme by combining experiments with simulation.It can accurately recognize multi-tone signals in 4.8GHz at a sampling rate of 0.2GS/s.Simulations found that this system is more Because of changes in compression ratio,it is more sensitive to changes in noise level,and excessive dispersion will cause system performance degradation.(2)On the basis of simulation,the system parameters are designed to build an experimental platform,the measurement matrix is constructed using multi-mode optical fiber randomly coded spectrum,and the calibration method is studied.Test system performance,and finally realize the reconstruction of single-tone signals in 25GHz with 15GS/s sampling rate,and the perceptual recognition of multi-tone signals in 9.6GHz with 4.8GS/s sampling rate.The recognition error is?100MHz.An in-depth analysis of the factors affecting system performance was made,and an improvement plan was proposed.In addition,experiments found that the current system is not sensitive to changes in the length of multimode fibers within 2 meters.This system has the characteristics of large sensing bandwidth,simple structure,low cost,and real-time sensing of single measurement.It has great application prospects in the face of complex and changeable electromagnetic environment,and has reference significance for the research of miniaturized and integrated equipment in the future.