Microwave Displacement Sensing Based on Slot Antenna Over Metasurface and Its Applications for Automatic Trolling Motor

This letter presents a microwave displacement sensor based on a slot antenna integrated with a solar panel metasurface. By leveraging near-field coupling between the antenna and metasurface, the sensor achieves dual-band operation (f₁ = 1.59 GHz/f₂ = 2.37 GHz) with high sensitivity, enabling non-contact monitoring of distance, orientation, inclination, and obstructions. The solar panel in the trolling motor's power unit acts as a metasurface at microwave frequency. Its coupling with the control unit's antenna installed above the solar panel senses the antenna displacement that is in synchronous movement with the motor. Experiments reveal distinct displacement sensitivities (−5.0 MHz/mm for f₁, −9.0 MHz/mm for f₂) and quasi-linear orientation responses (2.11 MHz/° for f₂). Frequency shifts under rotation (70 MHz for f₁, 190 MHz for f₂) and inclination (5.0 MHz/° for f₁) demonstrate robust multi-axis detection, while obstruction tests highlight resilience in dynamic environments. Based on these dual frequency matching changes, a sensing approach is validated conducive as to anti-interference attitude estimation of the trolling motors’ automatic operation, addressing the need for durable, humidity-resilient, high-precision sensing in aquatic applications.