便携式近地表FDEM观测系统抑噪方法研究

便携式近地表FDEM观测系统无法得到广泛应用，噪声干扰是关键问题之一。本项目提出便携式近地表FDEM观测系统内噪声与系统外噪声抑制相结合，收发数据互相关与“加-减抖动”（简称redithering）相结合的同步抑噪机制及方法。主要创新研究包括：1）基于逆重复m序列的收发数据互相关方法，将信号“内外结合”抑制“外”部不相关噪声；2）逆重复m序列与dither噪声相结合的噪声抑制方法，其中包括将dither噪声引入至ADC量化信号与数据运算中形成redithering机制，以实现“内”部噪声抑制；3）结合Goertzel算法实现弱信号提取，以有效优化仪器系统“内外”噪声同步抑制所消耗的时间与资源。通过本项目研究，以期提升便携式近地表FDEM观测系统探测性能，实现其在较强噪声环境中获得有效探测数据，同时为电磁法地球物理仪器提供新的抑噪机制与方法。

The noise suppression has primary responsibility for the portable near-surface frequency domain electromagnetic (FDEM) prospecting system has not yet being attained abroad application. A mechanism that the internal and external noise will be suppressed synchronously for the portable near-surface FDEM prospecting system is proposed, which combines the noise outside the system (external noise) with the inner noise analysis, as well as combines the sending and receiving data cross-correlation processing with the "add - reducing dither" (redithering) method. The major innovation parts in this project include: 1) A method for the sending and receiving data cross-correlation processing based on the invert-repeated m-sequence is proposed, which combines the system inner signal with the external signal to suppress the non-relevant external noise; 2) A noise suppression method that combining invert-repeated m-sequence with the dither noise is proposed, which includes the redithering mechanism formed by introducing the dither noise into the ADC quantized signal and the data operation to suppress the inner noise. 3) An approach to calculate frequency, amplitude, phase parameters of the system basing on Goertze algorithm is given to optimize the consumed time and computing resources when the inner and external noise are suppressed synchronously. The purpose of this research is to improve the detection performance of the portable near-surface frequency domain electromagnetic (FDEM) prospecting system, so as to obtain effective detection data in noisy environment, and provide new noise suppression mechanism and technology for electromagnetic geophysical instruments.