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The Ground-Air Frequency Domain Electromagnetic Method (GAFDEM) is a fast and effective semi-airborne electromagnetic exploration method for subsurface anomaly targets. Based on the depth-focused transmission waveform, this method can realize the high-resolution detection of underground targets at specific depths. However, due to the high inductance and resistance parameters of the transmitting load in GAFDEM exploration, the transmission current of the depth-focused waveform decays rapidly in the middle and high-frequency bands, which restricts the detection signal intensity. To solve this problem, a broadband resonant circuit and its parameter design method are proposed. According to the typical transmission frequency range and load, the parameters are designed, and the circuit model is simulated and tested. The results show that the designed broadband resonant circuit can increase the transmission active power of the depth-focused waveform by more than 490%, reduce the reactive power by more than 37%, and increase the transmission current intensity of the target frequency by 2.64 times. Moreover, this circuit has good robustness. It can achieve a good resonance effect within the error range of ±10% of capacitor. This design provides an effective way for GAFDEM to enhance the intensity of high-frequency detection signals and improve the shallow exploration effect.
Yu et al. (Wed,) studied this question.