基于相敏检测原理,推导出多频相敏检测的算法.在频域内分析了数字平均滤波器的响应特性,得到多频检测时采样频率、采样点数以及信号频率之间的约束关系.仿真实验结果表明,在信噪比低至-10 dB时幅度检测误差控制在0.5％以内,相位检测误差控制在0.2％以内.实际测井仪器数据采集系统设计中尽可能提高采集信号的信噪比,采集参数选择满足约束关系,从而实现多频信号高精度检测.%Based on the principle of phase-sensitive detection, the multifrequency digital phase-detection algorithm is developed. The digital average filter response is analyzed, the constraint relations hctween sample frequency, sample numbers and signal frequency are obtained. Simulation results show that amplitude detection error is controlled within 0. 5% and phase detection error is controlled within 0. 2% when S/N is —10 dK. In practical log data acquisition system design, the N/S of the acquired signals should be enhanced and the selected acquisition parameters should satisfy the constraint relations so as to realize better multi-frequency log signals detection.
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