The high-performance transient electromagnetic method (TEM) excitation source is a new type of source that has been proposed for urban underground space exploration. This source is composed of two trapezoid plates. To ensure that the radiation field was focused in a certain direction, the two trapezoid plate-shaped antennas were arranged into a horn shape. This new source is characterised by high power, directional excitation and high resolution. The corresponding multi-component global apparent resistivity definition method is established for a high-performance transient electromagnetic excitation source. This method is studied using the inverse function theorem. Then, the monotonic relationship between components of the electromagnetic field and resistivity is analysed. For the fields that satisfy the monotonic relationship with half-space resistivity, the apparent resistivity can be calculated correctly to ignore the time period and location in the space. This means that this definition method can eliminate the limitation of early and late times, and the near and far zones. The apparent resistivity calculation results of the theoretical layered model reveal that global apparent resistivity curves show a regular change, which smoothly and comprehensively reflects the change of electrical information in the model. The experimental results of the 3D model show that the five-layer low-resistivity anomaly contained in the urban underground space designed in this paper exhibits an obvious response in the global apparent resistivity profile. It is concluded that a high-performance TEM excitation source possesses a high resolution, clearly reflecting all of the anomalies of a complex urban underground space model.

中文翻译：

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高性能TEM激励源的全局视在电阻率定义

高性能瞬变电磁法（TEM）激发源是已提出用于城市地下空间勘探的新型源。该源由两个梯形板组成。为了确保辐射场聚焦在某个方向上，将两个梯形板状天线布置成喇叭形。这种新的光源具有高功率，定向激励和高分辨率的特点。针对高性能瞬态电磁激发源建立了相应的多组分总视在电阻率定义方法。使用逆函数定理研究该方法。然后，分析了电磁场分量与电阻率之间的单调关系。对于满足与半空间电阻率单调关系的场，可以正确计算视在电阻率，而忽略时间间隔和空间中的位置。这意味着该定义方法可以消除早期和晚期以及近端和远端区域的限制。理论分层模型的视在电阻率计算结果表明，整体视在电阻率曲线呈现规律性变化，可以平滑，全面地反映模型中电信息的变化。3D模型的实验结果表明，本文设计的城市地下空间中包含的五层低电阻率异常在全球视电阻率剖面中表现出明显的响应。