Research On Modulation And Demodulation Algorithm Of Mud Pulse High Speed Remote Transmission System

With the advancement of petroleum exploration technology,the continuous wave pulse system has become the main research technology of current measurement while drilling with high transmission rate.For complex and variable drilling environments,the signals collected on the ground will contain various background noises.In order to ensure the communication requirements of the system,it is of great significance to improve the processing of mud pulse signals.In this paper,the modulation and demodulation technology of continuous wave pulse system is the main research object.The characteristics of system noise and mud channel are taken as auxiliary research objects.The characteristics of mud pulse signal and the selection of modulation mode are selected.The mud pulse signal is based on RLS decision feedback equalization technology.The matched filter demodulation,the algorithm based on Duffing chaotic oscillator for demodulating mud pulse signal and the construction of mud pulse detection system are studied.The main research contents are as follows:1.The transmission speed of the mud pulse signal is analyzed.According to the noise composition of the measured data analysis system,combined with the working principle of the oscillating shear valve type continuous wave pulser,the mechanism of the mud pulse signal generation is given.From the aspects of reducing the difficulty of signal generation,reducing the attenuation and improving the anti-noise performance,the reasons for selecting the binary full-cycle frequency shift keying(FSK)continuous phase modulation method are analyzed.2.The matched filtering demodulation method is used to demodulate and analyze the mud pulse signal.According to the 3000 m water circulation pipeline used by COSL,the delay,attenuation and frequency selectivity characteristics of the mud channel are given.The decision feedback equalizer is combined with the RLS algorithm by matched filtering.Eliminate severe inter-symbol interference between signals and achieve coherent demodulation of mud pulse signals.3.According to the theory of Duffing chaotic oscillator detection signal,according to the characteristics of FSK modulation signal,the detection model of FSK signal detection based on Duffing chaotic oscillator is established,and the demodulation performance of single chaotic vibration subsystem and double chaotic vibration subsystem is simulated respectively.On this basis,the Duffing chaotic oscillator detection system is applied to the mud pulse signal demodulation,and the signal is processed accordingly to meet the vibrator detection conditions,and compared with the traditional coherent demodulation performance,the demodulation performance of the method is adopted.Significant improvement.4.The mud pulse transmission system includes the downhole signal generator,the drilling fluid channel,the ground signal acquisition system and the signal detection system.The signal detection system is emphasized and the simulation platform is built.The method of using Chirp signal to realize signal frame synchronization is analyzed in detail.Since the quality of the signal is closely related to the modulation and demodulation,the motor output signal is analyzed by the power spectrum,and the quality of the motor output signal is judged based on the harmonic component.