A planar-omnidirectional sensor for broadband and high-frequency underwater acoustic applications

Abstract

A prototype hydrophone with planar-omnidirectional radiation characteristics has been developed for broadband, high-frequency, underwater acoustic applications. A 9-μm sheet of KYNAR-type polyvinylidene fluoride (PVDF) was wrapped about a 2.5-mm solid Rho-c rod with a height of 86 mm such that the resulting cylindrical shape had an omnidirectional radiation behavior in the X-Y plane. The PVDF was oriented with the 3-1 direction radially wrapped and the 3-2 axis positioned along the mounting rod for improved vibration strum rejection from the mounting rod with improved radial sensitivity because of the orthotropic nature of the KYNAR material. Further discussions will detail the selection of an impedance matching mounting rod and waterproofing elastomer and a cable with the low capacitance of 0.018 pF/m (8.5 pF/ft). Measured data to be shown includes the free-field voltage sensitivity (FFVS) and X-Y plane receiving radiation patterns from 100 kHz to over 1.5 MHz. The presentation will conclude with a conceptual discussion on an advanced version of this same sensor design for a broadband and high-frequency, three-dimensional omnidirectional sensor.