基于旋转阀的钻井液连续波抗波形失真的信号调制优化研究

Study on Influencing Factors of Mud Continuous Wave Distortion Based on Rotary Valve

钻井液连续波传输技术以正弦压力波为载波,以井下测量数据为调制信号,通过对波形幅度、频率或相位的优化调制实现高速数据传输,但转阀的控制逻辑和发生器的实现方式难度高。本文基于旋转阀的连续波钻井液脉冲系统波形失真模型,对2FSK、2PSK和QPSK三种数字调制方式在波形失真情况下的误码率进行分析。结果表明:在载波频率为20 Hz,比特速率为5 bit/s,信噪比为6 dB的调制参数下,只2PSK和QPSK才能控制在1%以内的误码率性能;QPSK调制更快,且在10 bit/s的高传输速率下也能将误码率控制在1%以内,因此更适用于高速率传输的应用场合,故优选QPSK调制。另外,提出了解调时对码元过渡时间、载频误差、相位漂移的控制要求。

High-speed data transmission can be realized by mud continuous wave transmission technology through using the sinusoidal pressure wave as the carrier wave, taking the downhole measurement data as the modulation signal, and by optimizing the modulation of the waveform amplitude, frequency or phase.However, the control logic of the rotary valve and the realization method of the generator are difficult.Based on the waveform distortion model of continuous wave mud pulse system with rotary valve, the bit error rate of 2FSK,2PSK and QPSK digital modulation modes under waveform distortion is analyzed in this paper.The results show that only 2PSK and QPSK can achieve 1% error rate under the modulation parameters of 20 Hz carrier frequency, 5 bit/s and 6dB signal-to-noise ratio, but QPSK modulation is faster, and QPSK modulation can also achieve 1% error rate under high transmission rate of 10 bit/s.Therefore, QPSK modulation is more suitable for high-speed transmission applications, so QPSK modulation is preferred.The control requirements of time modulation for symbol transition time, carrier frequency error and phase drift are proposed.