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Enhanced Dynamic Range, Single-tone Cw Ultrasonic Ranging System

IP.com Disclosure Number: IPCOM000062795D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Munce, AC: AUTHOR

Abstract

In ultrasonic ranging, continuous-wave (CW) and pulse-echo are two basic modes of operation commonly used. Both measure distance between a known sound source and some acoustically reflecting target by measuring in some way the round trip tim flight of an acoustic wave between the source and the target.

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Enhanced Dynamic Range, Single-tone Cw Ultrasonic Ranging System

In ultrasonic ranging, continuous-wave (CW) and pulse-echo are two basic modes of operation commonly used. Both measure distance between a known sound source and some acoustically reflecting target by measuring in some way the round trip tim flight of an acoustic wave between the source and the target.

In a CW system, small changes in phase of the reflective wave determine the distance. The phase change, Wc, is given by

(Image Omitted)

where "L" is the measured distance of interest. Since phase change can be accurately measured, such systems can have high resolution on the order of g x 10-5 . However, the dynamic range of a CW system is limited, typically by the wavelength of the signal used. If the distance to be measured is less than wavelength g,the ambiguity which arises in the measurement of phase is avoided.

In pulse echo systems, resolution is lower and response time is slower but the dynamic range is greater. Resolution is limited by the ability to produce short well-defined acoustic pulses and related signal-to-noise ratio. Response time is limited not only by the round trip travel time of the pulse, but also by the transient settling time of the system.

A modified CW single tone system employing a variable frequency source which combines the advantages of high resolution and large dynamic range is proposed. Referring to the Figure, a phase-lock loop (PLL) is used for controlling the freque...