Accurate digital time-of-flight measurement using self-interference

Most ultrasonic distance measurements are based on the determination of the time of flight. This paper presents a novel way for the measurement of the time of flight, based on the detection of the envelope zero in an ultrasonic wave. A particular wave form is produced by supplying two pulse trains subsequently to an acoustic transducer. Distance information is retrieved from the zero, so a fully digital measurement is possible, reducing signal-processing time and resulting in a fast and accurate distance measurement.< >