Adaptive Filtering And Fast Implementation Of Mud Channel Noise In MWD System

In the development of petroleum field,the requirement of transmission rate of downhole information is increasing with the development of measurement technology.In this case,compared with other pulse generators,the continuous wave mud pulse generator has stable performance and high signal transmission rate.Therefore,continuous wave mud pulse transmission has become an important development direction of current MWD system.Although scholars at home and abroad have to cw mud channel interference signal filtering method carried out some research,and made relevant progress,but at present domestic MWD channel for cw mud channel interference and noise of the adaptive filter’s research also is less,this paper research purposes is based on the research of adaptive filtering algorithms,constructing adaptive denoising system,from mixed with strong interference and noise of the signal in real time detect the useful signal to make a beneficial attempt.Combined with theoretical derivation,software simulation and hardware design,this paper proposes an improved variable step size LMS algorithm for continuous wave mud channel signal characteristics to remove continuous wave mud channel noise.At last,DSP chip is taken as the core to complete the adaptive filter implementation and realize the adaptive noise cancellation function.The main tasks completed are:In this paper,the development of adaptive filter and related theories are summarized,the LMS algorithm for adaptive filter implementation is theoretically deduced,and the related parameters affecting the algorithm performance are theoretically analyzed.In view of the contradiction of the stability and convergence speed of the algorithm on the value of step size parameters,several variable step size LMS algorithm are studied,and an improved variable step size LMS algorithm is proposed.Through MATLAB simulation experiments,it is verified that the improved variable step size algorithm proposed in this paper has good performance in the application of adaptive noise cancellation and can effectively improve the noise elimination performance of adaptive filter.Determine the overall design of adaptive filter system.The program design of adaptive filter is completed,which mainly involves the realization of signal conditioning circuit and adaptive algorithm based on DSP chip.Then,the data acquisition and processing software of the upper computer’s mud while drilling channel is completed,which mainly involves the setting and application of FFTW library.Finally,the system performance of the designed adaptive filter system is tested to verify its performance.