Research On Multi-Path Separation And Diversity Reception Method Of Elastic Wave Teceivers At Stratum Propagation

In this thesis, we focus on the multipath propagation characteristics of elastic waves in the earth channel. In the case where the source signal has not changed and changed, the multipath separation and diversity reception of the elastic wave signal are carried out by the methods of the RAKE reception and blind source separation. The signal to noise ratio of the elastic wave receiver is improved. And the communication quality is inmoved.Firstly, the multipath propagation characteristics of the elastic wave in the earth channel are analyzed. The basic theory of elastic wave propagation is studied. The propagation characteristics of elastic waves in the formation is analyzed. The multipath effect model of stratigraphic transmission elastic wave is established. The multipath propagation of elastic waves is simulated by Matlab and Comsol. The correctness of the model was verified. The simulation results show that as the thickness of the coal seam increases, the longer the delay of the reflected wave of the elastic wave relative to the direct wave. And with the increase of time,the attenuation of the elastic wave energy is close to the exponential decay.Secondly, the elastic wave multipath separation and diversity reception of the inherent characteristics are studied. The current approaches of diversity and merging are analyzed and compared. The path diversity method is selected to obtain the independent multipath signal, and the maximum ratio combining method is used to receive the multipath signal. Moreover, the Rake reception scheme of elastic wave multipath signal is designed. A model of elastic wave RAKE is established and simulated by Matlab software. The simulation results show that RAKE reception can effectively solve the multi-path problem of elastic wave and improve the signal to noise ratio of the receiving end.Finally, multipath separation and diversity reception of the elastic wave of variation source are studied. The blind source separation model of elastic wave multipath signal is established. Meanwhile, the blind source separation algorithms based on global optimal and maximum signal to noise ratio are studied. The two algorithms are simulated by Matlab software. The simulation results show that both algorithms can separate multipath signals. But the blind source separation algorithm based on maximum signal to noise ratio is better than the blind source separation algorithm based on global optimal.