Controlled source ultra-audio frequency magnetotellurics transmitter for high-resolution detection of urban shallow underground space

Controlled-Source Audio-frequency Magnetotellurics (CSAMT) is an important method for obtaining shallow subsurface geological information. Achieving high-resolution shallow electromagnetic imaging requires high-frequency transmission (>100 kHz), but cable reactance limits current emission. This study develops a miniaturized, controlled source ultra-audio-frequency magnetotellurics (CSUMT) transmitter utilizing SiC MOSFETs and specialized driving circuit for stable high-frequency operation. The system incorporates an innovative tunable resonant control module that enables sufficient current emission without requiring high power input or bulky equipment. Field experiments conducted at geologically distinct sites in Beijing and Shaanxi demonstrated the system’s robust performance across the 10 kHz-600 kHz frequency range. Experimental results confirmed excellent signal reproducibility and consistency, with received signals maintaining > 50 dB signal-to-noise ratio (SNR) and less than 3 % deviation in both SNR and apparent resistivity measurements across multiple surveys. This technology provides critical support for high-resolution imaging of shallow and middle-depth underground structures.