# Miniaturizing Controlled-Source EM Transmitters for Urban Underground Surveys: A Bipolar Square-Wave Inverter Approach with SiC-MOSFETs

## TL;DR

This paper introduces a compact, efficient electromagnetic transmitter for urban underground surveys using a new inverter design with SiC-MOSFETs.

## Contribution

A novel bipolar square-wave inverter topology is proposed, reducing system losses and size for CSAMT applications.

## Key findings

- The design achieves simulated efficiency greater than 90% and reduces volume and weight by 40%.
- The system meets EN55032 Class A EMI standards and enables high-resolution subsurface imaging.
- Field tests confirm effective signal transmission and improved portability for urban geophysical exploration.

## Abstract

This paper presents a compact, high-efficiency electromagnetic transmitter for Controlled-source Audio-frequency Magnetotelluric (CSAMT) applications, operating in the 10–100 kHz range. A novel bipolar square-wave inverter topology is proposed, which directly modulates the transformer’s secondary-side AC output, eliminating conventional rectification and filtering stages. This design reduces system losses (simulated efficiency > 90%) and achieves an approximately 40% reduction in both volume and weight. The power stage uses a full-bridge bipolar inverter topology with SiC-MOSFETs, combined with a high-frequency transformer for voltage gain. Simulation, laboratory testing, and EMI evaluation confirm stable square-wave generation and full compliance with EN55032 Class A standards. Field validation with a CSAMT receiver demonstrates effective signal transmission and high-resolution subsurface imaging, thereby improving the efficiency and portability of urban geophysical exploration.