High precision, short range ultrasonic sensing by means of resonance mode-locking |
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Authors: | J Tapson |
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Institution: | School of Electrical Engineering, Cape Technikon, Box 652, Cape Town 8000, South Africa |
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Abstract: | This report describes a novel method of continuous-wave operation of ultrasonic transducers, which enables short-range measurement with a resolution much finer than the sound wavelength. The transducer is locked into a particular resonant mode of the transducer-gap-reflector system by a resonance-locking phase-locked loop. The resonant frequency depends on the relative coherence of the transmitted and reflected waves, so that a change in the position of the reflecting surface will require a corresponding change in the resonance frequency if the resonant mode is to be retained. A simple system of this type has been implemented using a cheap, commercially available transducer with far-from-optimum characteristics. The system has been found to operate successfully in a range well below the typical ring-down range of a corresponding pulse-echo system, and has displayed a resolution much finer than the sound wavelength for the transducer. |
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Keywords: | industrial sensors air transducers mode-locked transducers subwavelength resolution |
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