Research on Shaping Control Method of Transient Electromagnetic Transmission Current

The electromagnetic method is crucial for geophysical exploration, especially in the surveying of mineral and energy resources. The transient electromagnetic (TEM) transmission system, as the core component of electromagnetic detection equipment, directly affects the accuracy of detection results and the stability of the equipment. In high-power ground-air electromagnetic transmission systems, the rising and falling edge characteristics of bipolar square wave current pulses significantly impact the transmitter's performance. To shape the transmission current waveform, this study proposes a new circuit design that includes impedance matching preloading for the rising edge and an active constant voltage clamping technique for the rapid turn-off of the falling edge. This circuit topology can reduce the overshoot of the rising edge by preloading the transmission load impedance matching circuit before the current rises and achieve rapid turn-off through active constant voltage clamping when the transmission current falls, thereby comprehensively improving the quality of the electromagnetic transmission waveform. The effectiveness of the proposed circuit topology and control strategy has been verified through simulation experiments using MATLAB/Simulink.