Characterization and Mitigation of Thruster-Induced Electromagnetic Noise on Underwater Wireless Communication

Abstract

Underwater radio communication has the potential to complement conventional underwater communication methods, such as acoustic and optical systems, which suffer from limited bandwidth and strict alignment requirements, particularly for short-range and real-time robotic applications. However, its practical deployment in underwater robotic platforms is hindered by electromagnetic noise generated by onboard components, which significantly degrades communication performance and has not been systematically evaluated. In this study, we experimentally investigate electromagnetic noise generated by a thruster system in an underwater robot from the perspectives of conducted and radiated emissions. Conducted noise is measured using a line impedance stabilization network (LISN) with common-mode (CM) and differential-mode (DM) separation, while radiated noise is evaluated using a loop antenna in an anechoic chamber. The results reveal that the thruster system generates strong comb-shaped noise spectra with a spacing of 160 kHz, corresponding to the switching frequency of the motor controller. These findings demonstrate that the thruster system is a dominant source of electromagnetic interference (EMI) that directly degrades underwater radio communication performance. To mitigate these effects, line filters and a shielding structure are introduced. The line filters substantially reduce conducted noise over a wide frequency range, with reductions exceeding 30 dB at many frequency components, while the proposed shielding achieves up to 20 dB reduction in radiated noise. These results provide a systematic understanding of thruster-induced electromagnetic noise and offer practical design guidelines for achieving reliable underwater radio communication in underwater robotic systems.