延时叠加工频谐波消除系统设计与实验

Design and Experimentation of Eliminating Harmonics Based on MRS Response

针对全波核磁共振信号中的噪声,尤其是最接近拉莫尔频率的工频谐波噪声干扰,影响核磁共振信号的采集及测试结果。设计了延时采样、叠加抵消的消噪方法,理论计算了对同一位置的信号相差半个最接近拉莫尔频率的工频谐波信号周期的两组信号,分别提取并叠加,可以消除拉莫尔频率附近的工频谐波噪声的算法。仿真结果表明,采用设计的消噪方法,信噪比可以提高6.9 dB。采用实际电路测试信号,实测结果与仿真结果对比基本一致。结果表明,该设计可以消除最接近拉莫尔频率处的工频谐波噪声,从而有效的提取核磁共振信号,保证了反演解释的正确性和准确性。

For the full wave noise in nuclear magnetic resonance signal,especially the closest to the Larmor frequency harmonic noise,we design a method of sampling delay and superposition offset.The signals at the same position but difference frequencies which are half frequency near Larmor harmonic signal cycle are extracted and superposed to eliminate the noise.The simulation results show that the method improves SNR is 6.9 dB.The design can completely eliminate noise of the closest Larmor frequency harmonic frequency through actual measurement,its near frequency harmonic noise can be removed partly,and can effectively extract MRS signal and ensure the correctness and accuracy of the inversion interpretation.