ACCURATE DIGITAL TIME-OF-FLIGHT MEASUREMENT USING SELF-INTERFERENCE

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