Circuit and system design of a silicon-based miniaturized ultrasound range finder system

An ultrasound ranging system using resonant silicon membrane transducers operating at 100 kHz is described. The ultrasound transducers consist of a 1 mm by 1 mm silicon membrane of 5-6 μm thickness which can be excited thermally to generate ultrasound pressure or detect incident ultrasound by a piezo resistive Wheatstone-bridge. To perform the distance measurement in a 10-100 mm range with a 4 mm resolution, a novel measurement principle based on a Δf phase-shift method has been developed and verified experimentally. The frequency and the phase of the emitted ultrasound are fully controlled by the use of phase-locked-loop circuits and a self-calibrating scheme applied to the receiving membrane allows maximum sensitivity and phase accuracy