Research On The Influence Of Pressure Carrier Frequency Distortion On Drilling Fluid Pressure PSK Signal Modulation And Transmission

The continuous pressure wave telemetering technology of drilling fluid has the characteristics of strong anti-interference ability and high transmission speed.The continuous pressure wave signal of drilling fluid is a kind of band transmission signal,in which the drilling fluid pressure phase shift keying(PSK)modulation is widely used because of its high data transmission efficiency.The drilling fluid pressure PSK signal is produced by the data modulation of the phase of the pressure carrier,and the quality of the carrier wave directly affects the quality and the letter of the modulated signal.The transmission effect of the number.Therefore,the influence of carrier distortion on drilling fluid pressure PSK modulation and signal transmission characteristics has important theoretical guiding significance for the research and development of underground information telemetry system.Because of the low pass characteristics of the drilling fluid channel,the attenuation difference between different frequency components in the frequency band signal is caused.The signal is distorted after long distance transmission and the signal waveform is distorted.Therefore,how to accurately describe the transmission characteristics and distortion of the signal is the key.In this paper,a study based on the viewpoint of energy analysis is made.To solve this problem.According to the structure of the rotary valve,the wave characteristics and frequency characteristics of the drilling fluid pressure carrier produced by the rotary valve are calculated and analyzed theoretically,and the influence of the constant number of the speed time of the rotary valve rotor speed tracking speed control pulse on the phase shift function in the PSK modulation process of the drilling fluid pressure is studied by mathematical modeling.The frequency distortion of the carrier and the influence of the rotational speed constant of the rotary valve on the PSK modulation of the drilling fluid pressure,the mathematical model of the drilling fluid pressure PSK signal under the influence of the two is constructed,and the transmission of the drilling fluid pressure PSK signal is studied based on the energy analysis view by establishing the time domain model of the PSK signal with the energy normalization downloading the frequency distortion.Characteristics and distortion.The study shows that the carrier distortion has a great influence on the signal energy of the modulated signal modulation distribution in the total energy of the modulated signal.Whether it is a drilling fluid pressure differential shift keying(DPSK)signal or an orthogonal phase shift keying(QPSK)signal,the energy of the fundamental modulation signal is not more than 50% of the total signal energy,because the fundamental modulation signal is required.The low energy of the base wave modulation signal will greatly influence the long distance transmission of the drilling fluid pressure PSK signal.The rotational speed time constant of the rotary valve will change the pressure carrier wave in the phase modulation,resulting in the distortion of the drilling fluid pressure PSK signal,and the rotational speed time constant is produced by the drilling fluid pressure QPSK modulation production.The signal distortion of the raw signal is far greater than the DPSK modulation;compared to the calculation of the transmission coefficient and the distortion degree by the harmonic description,the calculation results of the transmission coefficient and distortion of the drilling fluid pressure PSK signal based on the signal energy analysis can reflect the transmission characteristics of the signal more accurately and the transmission characteristic of the signal more accurately.The change of the time domain waveform of the signal.