Early-time measurements of time-domain electromagnetics carry information of the near surface, and therefore, the interpretation of such measurements is important, particularly when utilizing small-loop acquisition devices. However, these early-time gates are often distorted by responses from the acquisition system itself, primarily caused by self-transients associated with the transmission link composed of the transmitter and receiver loops and with the investigated medium electrical properties. Estimating all such potential couplings is crucial for interpreting early-time measurements and gathering information on the near surface. In this study, a receptor loop made of 20 turns was built for this purpose. Field results and simulations were then compared, which shows how full-wave finite-difference method in the time-domain simulations can be used to accurately calculate the impedance characteristics of time-domain electromagnetics systems. All simulations were performed using finite-difference time-domain software based on a fully explicit three-dimensional solver. First and second sets of simulations, respectively, were carried out in free space to compare the results to an alternate simulation method with equivalent lumped electrical circuits and on a homogeneous half-space with varying electrical resistivities. The results were then used to improve the inversion of field data acquired on a test site in Garchy, France.

中文翻译：

---

时域电磁学早期测量的全波建模：考虑 Tx-Rx 天线与地面之间的耦合

时域电磁学的早期测量携带近地表的信息，因此，对此类测量的解释很重要，尤其是在使用小回路采集设备时。然而，这些早期门通常会因采集系统本身的响应而失真，这主要是由与由发射器和接收器环路组成的传输链路以及所研究的介质电特性相关的自瞬变引起的。估计所有此类潜在耦合对于解释早期测量结果和收集近地表信息至关重要。在这项研究中，为此目的构建了一个由 20 圈组成的受体回路。然后将现场结果和模拟进行比较，它展示了如何使用时域仿真中的全波有限差分方法来准确计算时域电磁系统的阻抗特性。所有模拟均使用基于完全显式三维求解器的有限差分时域软件进行。第一组和第二组模拟分别在自由空间中进行，以将结果与具有等效集总电路和具有不同电阻率的同质半空间的替代模拟方法进行比较。然后将结果用于改进在法国加希的测试站点上获得的现场数据的反演。所有模拟均使用基于完全显式三维求解器的有限差分时域软件进行。第一组和第二组模拟分别在自由空间中进行，以将结果与具有等效集总电路和具有不同电阻率的同质半空间的替代模拟方法进行比较。然后将结果用于改进在法国加希的测试站点上获得的现场数据的反演。所有模拟均使用基于完全显式三维求解器的有限差分时域软件进行。第一组和第二组模拟分别在自由空间中进行，以将结果与具有等效集总电路和具有不同电阻率的同质半空间的替代模拟方法进行比较。然后将结果用于改进在法国加希的测试站点上获得的现场数据的反演。