68 element projector-receiver array for parametric sonar

A 68 element transmitter-receiver array operating around 80 kHz has been designed and fabricated for parametric sonar applications. The projector array consists of sixteen staves of four elements each provide a beam-width of 5 degrees in bearing and 18 degrees in azimuth. The elements are made with PZT-6 material to handle large powers. The array transmits dual frequency signals simultaneously in the same direction at high powers. These signals interact in the medium and generate the difference and the sum frequency signals, the difference frequency signal which has the same directivity is now used to detect or visualise the underwater objects. The received signals which range between 1 MHz to 5 kHz are picked up on a low frequency broad bandwidth hydrophones. The array also has a seventeenth stave of four elements which is used for receiving the signals at primary frequencies. The array has been characterised for its transmitting response and receiving sensitivity