Ch. Cai et Ppl. Regtien, ACCURATE DIGITAL TIME-OF-FLIGHT MEASUREMENT USING SELF-INTERFERENCE, IEEE transactions on instrumentation and measurement, 42(6), 1993, pp. 990-994
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.