钻井液压力脉宽及脉位多进制相移键控信号分析

在构建出钻井液压力脉宽及脉位多进制相移键控（MPSK）调制信号数学模型的基础上，分析了MPSK信号的频谱特性，从频域研究了将脉宽及脉位调制方式应用于钻井液压力MPSK信号传输的可行性。通过建立MPSK信号沿定向井钻柱分布的传递函数，研究了钻井液信道参数和调制方式对信号传输的影响。数值分析表明，钻井液压力脉宽MPSK调制信号的频谱主瓣带宽内信号的相对能量过低，从频谱角度看不适于频带传输;钻井液压力脉位MPSK调制可用于井下数据的频带方式传输，但信号的传输损失相对较大，因此对信号的检测、处理及旋转阀的转速控制要求较高。

Analysis of drilling fluid pressure MPSK signals for PWM and PPM

Signal frequency spectra were analyzed based on establishing a mathematic model for multiple phase shift keying (MPSK) signals for pulse width modulation (PWM) and pulse position modulation (PPM) of drilling fluid pressure. The feasibility of applying the PWM and PPM methods to transmit down-hole MPSK signals of drilling fluid pressure was studied in terms of frequency domain. Impacts of drilling fluid channel parameters and modulation methods on data transmission were examined by establishing transfer functions for the MPSK signal distribution along directional drill string. Numerical calculation results show that the relative energy of signals within the main-lobe bandwidth of MPSK signal for PWM of drilling fluid pressure is too low to fit the frequency-band transmission in terms of frequency spectra, while only the MPSK signal for PPM of drilling fluid pressure can be used for data frequency-band transmission. However, this transmission pattern usually has relatively stricter requirements for the signal detection, treatment and rotating speed control of the rotary valve because of a greater transmission loss.