volume | PIER Journals

Abstract

Unmanned aerial FPV systems demand ultra-low latency, high-reliability communication. At high speeds and in cluttered environments, Doppler shifts and rapid multipath changes significantly increase packet error rates (PER). This paper introduces a novel solution: real-time geometry tuning of a circularly polarized helical antenna array to mitigate these effects in ExpressLRS (ELRS) long-range FPV control links. Using full-wave simulations (Ansys HFSS) and blind field trials, we validate system performance. A new analytical framework integrates Doppler-induced frequency offset into the antenna's radiation pattern and PER model. The adaptive array autonomously adjusts coil pitch and diameter based on velocity and attitude, reducing PER by 20% at speeds over 150 mph. It also maintains near-unity VSWR, preventing reflection spikes, and halves RSSI variation, indicating improved link stability. These results demonstrate that tunable helical antennas can effectively mitigate Doppler and multipath impairments in high-mobility UAV environments, informing future antenna designs and supporting the development of AI-integrated, adaptive RF systems for drone racing and autonomous swarms.

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Mr. Ethan Chien

Dr. Jan Steckel