小尺寸TEM非共面偏心自补偿零耦合收发技术研究

Research on non-coplanar eccentric self-compensation zero-coupling receiving-transmitting technology for small size TEM

发射线圈对接收回路的耦合影响,是导致瞬变电磁(TEM)早期信号失真、浅层盲区大的主要因素之一,对于多匝小尺寸线圈结构,耦合影响更为严重。针对这一问题,提出了一种小尺寸TEM非共面偏心自补偿零耦合收发技术。该技术采用收发线圈非共面偏心的思路设计了一次场自补偿系统,非共面结构实现发射线圈与接收线圈的弱耦合,并基于互感理论获得二者的最佳相对偏心位置,以消除一次场干扰。对基于导电环异常体的探测模型进行实验仿真,结果表明新结构系统在收发线圈±2 mm尺寸误差内,能够忽略一次场的影响,对物理尺寸误差的容忍度较高,易于实现零耦合状态。最后,采用串连法对设计的非共面偏心自补偿TEM系统进行了实测实验,测试结果与理论分析一致,进一步验证新结构性能。研究可为小尺寸TEM系统获得纯二次场信号、提高浅层探测性能奠定理论基础。

The coupling effect of the transmitting coil on the receiving loop is one of the main factors that cause the early signal distortion of the transient electromagnetic method(TEM) and the large shallow blind area. For the multi-turn small-size coil structure, the coupling effect is more serious. Aiming at this problem, a non-coplanar eccentric self-compensation zero-coupling receiving-transmitting technique for small size TEM is proposed. This method adopts the idea of non-coplanar eccentricity of the receiving-transmitting coils to design a primary field self-compensation system. The non-coplanar structure realizes the weak coupling of the transmitting coil and the receiving coil, and the optimal relative eccentric position of the two coils is obtained based on the mutual inductance theory and the primary field interference is eliminated. The experiment simulation of the detection model based on the conductive ring anomaly was carried out. The results show that for the ±2 mm size error of the receiving-transmitting coils, the new structure system can ignore the influence of the primary field and has a high tolerance for physical size errors. Finally, the series connection method was used to carry out practical experiments on the designed non-coplanar eccentric self-compensation TEM system. The test results are consistent with the theoretical analysis, which further verifies the performance of the new structure. The research will lay a theoretical foundation for obtaining a pure secondary field signal in a small-sized TEM system and improving shallow detection performance.