Hardware Design, Range Optimization, and UAV Integration of an FMCW Ultrasonic Radar System

To make an FMCW ultrasonic radar idea survive contact with real boards, transducers, and a real multicopter.

Commercial fixed-tone time-of-flight modules are prone to interference; custom FMCW chirps to spread energy and reduce interference.

UAV obstacle avoidance and altitude holding during indoor autonomous flight.

This report describes the hardware-focused portion of an FMCW (frequency-modulated continuous-wave) ultrasonic radar built for unmanned aerial vehicles. The wider group effort spans additional software and learning-based components; here the emphasis is on the analog frontend, printedcircuititeration, benchvalidation, andairframeintegration. Commercial ultrasonics for small UAVs are convenient, but fixed-tone time-of-flight mod- ules are prone to interference and crosstalk when several units operate nearby. The custom sensor instead chirps across roughly 35–45 k Hz, digitizes the return on an STM 32 G 071, and recovers range via spectral analysis. My work concentrated on stretching usable range by re- tuning amplification and filtering, laying out a second-generation board that separates transmit and receive paths more cleanly, benchmarking the custom head against a standard HC-SR 04 on a fixed rig, mounting the assembly on a flying quadrotor with UART streaming to the flight controller, and keeping the analog chain healthy through a semester of repeated assembly, dis- assembly, anddemonstrationuse. The outcome is a flight-mounted prototype that held up under real conditions: measur- able improvement in interference behaviour relative tothe baseline sensor on the bench, stable UART telemetryinhovertests, andareceiverchainthatcouldberepairedandre-biasedquickly whenclassroomhandlingexposedweakspotsinprotectionandgrounding.