Tunable sonar transducer

Abstract

A prototype of a tunable sonar transducer has been successfully tested in the transmit/receive mode. It employs a tunable sandwich transducer which is a high-Q transmitter with resonance frequency that can be shifted continuously over a wide frequency range between the fundamental harmonic at 27?kHz and the first overtone at 73?kHz of the whole structure. The tunable sandwich transducer divides the active piezoelectric layer to two sets. The first is the control ceramic whose function is to vary the resonance frequency of the overall structure by using various values of inductor across its terminals. The control ceramic is mechanically coupled to the drive ceramic which provides the acoustic power during transmission and alternately acts as a receiver. From the transmit/receive measurements within the tunable frequency range, the receiving sensitivity of the tunable transducer may be varied between 0 and 9?μV/Pa. Generally, the receiving sensitivity is higher at the mechanical resonance frequencies and lower in the mid-frequency range. The receiving sensitivity of the tunable transducer at the fundamental harmonic is 9?μV/Pa (?221?dB re 1?V/μPa) which is similar to 11?μV/Pa (?219?dB re 1?V/μPa) for the sensitivity when driven as a conventional sandwich transducer.