Wideband Pulse Generation for Underwater Applications Using Parametric Array

We investigated wideband pulse generation for underwater acoustic applications using a parametric array. We fabricated a transducer consisting of a 3 mm thick 75 mm-by-75 mm square-shaped PZT ceramic plate, which is matched to water media at the radiating face and terminated by a very low impedance at the back. All measurements were made in a large test tank. We transmitted square-root amplitude modulated pulses centered around 855 kHz primary frequency. We showed that phase-sensitive generation of in-phase and out-of-phase bursts suitable for coded transmission using a parametric array is possible. We generated very short duration bursts, as short as half-cycle, at a 10-80 kHz difference frequency range. The definition of the bursts is excellent, e.g., with a normalized cross-correlation of 0.92 with an ideal 2-cycle square burst, for both in-phase and out-of-phase pulses.