便携式近地表FDEM观测系统抑噪方法研究

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.

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。

便携式近地表频率域电磁法（FDEM）观测系统作为有望广泛应用于浅层矿藏、泥石流、地下管线、地下水及污染、地下未爆炸地雷等近地浅层探测的仪器装备，具有快速、便捷的优势。经统计分析，由于大部分地区特别是城市及城郊电磁噪声过强，使其难以获得有效的数据。基于如上需求，本项目提出了结合互相关与redithering的仪器“内外”结合同步抑噪的框架理论与方法，并取得了一系列成果：1）提出了一种新的观测系统“内外”结合抑噪的理论，完成了技术途径实现，通过解决相应理论和其中的关键科学问题，提高了便携式近地表FDEM观测系统的性能和稳定性，解决强扰环境下近地表便捷勘测的探测能力瓶颈问题；2）研制了基于逆重复m序列的dither噪声源，形成完善的redithering处理机制，提升观测系统的SFDR指标，对截位造成的谐波失真噪声具有明显的抑制作用；3）基于已有基础，优化改进了观测系统样机1套，完成了应用实验验证，具有完善且可供参考的硬软件设计方案，提升了观测系统的重复精度、系统实时性、系统勘测分辨率等性能指标。项目执行期间，共发表标准论文11篇，其中SCI标注论文8篇、EI标注2篇，第一标注5篇、第二标注4篇，申请并被授权国家发明专利3项。

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