Research On Frequency Dispersion Compensation Method Of Coal Seam Channel Based On Frequency Domain Equalization

This subject comes from the National Natural Science Fund Project"Precise Detection Theory of Reflective Groove in Coal Seam Based on Continuous Seismic Source".According to the demand of this project,the channel wave transmitted through coal seam is processed according to the channel environment of coal seam,and then eliminate the influence of frequency dispersion.The purpose of this subject is to design the frequency domain equalization algorithm which could adapt to the frequency dispersive wave signal.At the same time,in order to estimate the parameters of the coal seam channel,the estimation of the compressed sensing channel is also studied.(1)This paper gives a detailed description of the research on channel wave dispersion by experts at home and abroad,summarizes the research in different directions.Then the development of the equalization algorithm and channel estimation technology at home and abroad is narrated.Next it studies the transmission characteristics of the trough wave,and determines the compression perception estimation model of the coal seam channel.The channel estimation method of coal seam under different conditions is expounded,and the theoretical basis of frequency domain equalization for eliminating slot wave dispersion is expounded.(2)The channel environment of coal seam is stable,and the channel wave signals which are transmitted in coal seam could be sparse expressed.Through the analysis of the characteristics of the coal seam channel,the compressed sensing channel estimation based on the hierarchical Bayesian model is be chosen to estimate coal seam parameters,and the Bayesian mathematical model and the sparse expression model of coal seam are derived in detail.The message updating algorithm of the model is studied,and then chosen the generalized approximate message updating algorithm of the joint mean field.The calculation method of the parameter matrix is improved what is from high dimension matrix calculation to low dimension matrix calculation,and delete the redundant data to reduces the complexity of the algorithm.Simulation results using Matlab show that the improved algorithm has lower complexity and the performance has also been improved.(3)The classical frequency domain equalization algorithm--block iterative decision feedback frequency equalization algorithm is studied and improved based on fractional Fourier transform.The basic principle of block iterative decision feedback equalization to offset trough wave dispersion is described,and the fractional Fourier transform is used to instead traditional Fourier transform.What's more,the optimal order selection method is designed,which can effectively adapt to the different frequency changes of the wavelet.According to the compressed sensing channel estimation algorithm and the frequency domain equalization algorithm proposed in this paper,the anti dispersion capability of frequency domain equalization system is simulated and analyzed by using Matlab.It can be seen from the signal waveform and spectrum diagram of the simulation results that the frequency domain equalization system can compress the broadened trough wave back to the original shape,and the broadened band can be compressed well,so it has strong anti dispersion performance.