A multi-frequency method for ultrasonic ranging

• Ultrasonic ranging based on the cross-correlation of two multi-frequency signals.
• Stimulus signal composed by sine-wave bursts, containing different frequencies.
• The frequency of each sine-wave burst is different from that of the adjacent bursts.
• Time-of-flight is estimated by finding the maximum of cross-correlation.
• Error corresponding to two standard deviations, for up to 1 m, is less than 0.3 mm.

This paper presents a method for ultrasonic ranging based on the cross-correlation of two multi-frequency signals. The stimulus signal is composed by multiple sine-wave bursts/segments, each containing a different frequency and an integer number of periods. The frequency of each sine-wave burst is different from that of the adjacent bursts, but it is very close to the transducer resonant frequency. The time-of-flight (TOF) is estimated by finding the maximum of the cross-correlation. Interpolation is used to increase the measurement resolution. The experimental error corresponding to two standard deviations, for a range up to 1 m, is less than 0.3 mm.