| 摘要 |
A transducer projects bursts of ultrasonic energy having broadbandwidths substantially identical to the energy pulses transmitted by a porpoise or dolphin. Immediately prior to the projection of the broadband ultrasonic signals, a range gate pulse is transmitted which, necessarily, first reaches the target and is reflected back toward a hydrophone carried adjacent the transducer-projector. At the termination of the reflected range gate pulse, the reflected broadband ultrasonic signals are gated into a pulse stretcher. During the relatively long intervals between the time that successive bursts of the broadband ultrasonic signals are projected or received, the pulse stretcher functions to translate and divide the broadband ultrasonic signals into signals lying within the audio spectrum. Due to the uniquely connected analog-to-digital, buffer storage, and digital-to-analog circuit components, the translation from the ultrasonic spectrum to the audio spectrum is done in a real-time basis to provide an audio representation having substantially the same information content as the ultrasonic signals.
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