| 摘要 |
PCT No. PCT/AU90/00489 Sec. 371 Date Jun. 17, 1992 Sec. 102(e) Date Jun. 17, 1992 PCT Filed Oct. 12, 1990 PCT Pub. No. WO92/08329 PCT Pub. Date May 14, 1992.An ultrasonic transducer has a pair of transducer elements (30,31), polarised in opposite directions, which are mounted between, and in intimate contact with, respective front face electrodes (32) and back face electrodes (33). The front face electrodes are each earthed. The back face electrodes are each connected to a respective input/output terminal (34,35). The input/output terminals are supplied with activating pulses of opposite polarity, produced using a differential pulse generator (39) or a transformer arrangement (43), when the transducer is operating in the transmit mode. When the transducer is operating in the receive mode, pulses of opposite polarity are generated at the back face electrodes when an ultrasonic pressure wave is incident upon the front face electrodes. These pulses are differentially summed using a differential amplifier (40) or a transformer arrangement (43). Impedance matching is preferably used to optimise performance. Such a transducer has a substantially reduced pick-up of environmental noise and thus has an improved signal to noise ratio when in use.
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