MRT核磁共振微弱信号采集处理方法

Signal Acquisition and Processing Method for MRT Logging Tool

核磁共振信号采集处理方法要满足CPMG时序实时性与回波高信噪比的要求。MRT多频核磁共振测井仪应用累加平均数字相敏检波算法实现信号检测,该算法基于FPGA实现并行加法计算,基于DSP实现单周期数字相敏检波运算,其主要特点是DSP读取数据时间和数据运算时间与采集数据量无关,算法信噪比与采集数据量成正比,数据量越大信噪比越高。该算法能够在信噪比低至-30^-60dB的噪声中实现微弱正弦信号幅度及相位估计,在满足CPMG时序实时性前提下,应用该算法得到的原始回波信噪比能够较好地满足仪器稳定性要求。

Data acquisition and processing method of NMR must meet the requirement of real-time of CPMG sequence and higher signal to noise ratio of echo.MRT logging tool applies cumulative average phase-sensitive detection algorithm to detect weak signals.The algorithm is based on FPGA to achieve addition and based on DSP to achieve single-cycle digital phase-sensitive detection.Its main feature is that the time to read and compute the data has nothing to do with the amount of data collected.SNR of the algorithm is proportional to the amount of data collected,therefore the larger the amount of data collected,the higher signal to noise ratio.When the SNRis low to-30^-60 dB,The algorithm can estimate the weak signal amplitude and phase.The SNRof original echo signal obtained by the algorithm meets the requirement of the stability about instrument when the algorithm meets the real-time of CPMG sequence.