| 摘要 |
An embodiment of a sensing apparatus includes an ultrasonic delay sensor having a delay related to the sensed quantity; and a time domain analysis circuit for recirculating pulses through the ultrasonic delay sensor or device and for generating the output signal related to the sensed quantity. In particular, the time domain analysis circuit may include a pulse generator for generating a series of input pulses to the ultrasonic delay sensor; a pulse detector for detecting a series of output pulses after propagation through the ultrasonic delay sensor; and a pulse recirculating circuit for causing the pulse generator to generate the series of input pulses based upon respective previously detected output pulses from the pulse detector. The apparatus also preferably includes circuits for suppressing the undesirable reflections generated by the ultrasonic delay sensor. For example, random phase switching may be used for randomly switching phases of the series of input pulses to the ultrasonic delay sensor to thereby reduce undesired reflections. In addition, a fixed delay may be operatively connected between the pulse detector and the pulse generator. Also time diversity matching to the ultrasonic delay device may also be used to suppress the effects of undesired reflections. Method aspects of the invention are also disclosed.
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