High Resolution, High Frequency Ultrasonic Ranging in Air with pMUTs

Ultrasonic ranging with piezoelectric micromachined ultrasonic transducers (pMUTs) can be used in applications such as robotic systems and industrial machinery for precise distance measurements. This work presents a technique of operating pMUTs below the resonance frequency to obtain a wide bandwidth for high resolution time-of-flight (ToF) ranging. Digital signal processing was performed to remove the residual ringing at resonance and recover the wideband echo signal by bandpass filtering and cross-correlation in the frequency domain. The ToF was then determined after transforming back to the time domain. An array of pMUTs with resonance frequencies around 1.1 MHz was pulsed at 500 kHz, and a 4.3 µm standard deviation in ranging resolution was achieved with a pulse repetition frequency (PRF) of over 2 kHz. This enables ultra-precise non-contact distance or vibration measurements within a low-profile form factor.