High Resolution Time-of-Flight Measurement with Narrow-Band COTS Ultrasonic Transducers

Ultrasonic transducers (a pair of speaker and microphone) are extensively used in distance and wind speed measurements. The measurement of Time-of-Flight (TOF) between an ultrasonic speaker and a microphone dominates the accuracy. This paper presents a method to improve the TOF measurement accuracy using narrow-band commercial off-the-shelf (COTS) ultrasonic transducers. The method features the use of an experimentally captured waveform to correlate the transmitted and received signals and the use of a phase modulated ultrasonic signal. The method is experimentally evaluated to show that the proposal can significantly reduce the TOF measurement error, from 25.5% to 0.3%.