SonarLite: a Compact Analog Sensing System for Real-Time UAV Navigation in GPS-Denied Zones

This work presents a signal-domain analog sensing approach for autonomous UAV navigation in GPS-denied indoor environments. Unlike prior analog systems, which primarily focus on simple threshold-triggered detection, our system interprets echo amplitude and time delay variations to perform real-time range estimation using only analog hardware. The design incorporates a 555 timer-driven 40 kHz ultrasonic transmitter and a dual-stage amplified receiver with comparator-based decision logic. Range estimation is realized through oscilloscope-traceable signal dynamics, with experimental validation showing stable performance over a 5—30 dB SNR (Signal-to-Noise Ratio) window. Compared to HC-SR04 and microcontroller-based systems, our approach offers lower latency ($\sim \text{1}-5 \text{ms}$), higher noise resilience, and removes the need for ADC sampling or digital filtering. This analog signal modeling makes it particularly suitable for light-weight UAV platforms requiring fast and energy-efficient obstacle detection.