Composite curved linear array for sonar imaging: construction, testing, and comparison to FEM simulations

The design, construction, performance, and comparison to FEM simulation of a broadband 375 kHz, 100 element, composite based, 115 mm radius curved receive array is described. This array was designed for use in a forward-looking, mine-hunting application with 60, 1.5° beams scanning a 900 sector. A 150° sector can be scanned with beamwidths widening beyond the center 90°. The bandwidth was desired to be 250 kHz, centered at 375 kHz. This array was demonstrated using an imaging system constructed by UDI-Fugro as part of a TTCP collaboration. The array was designed by Ultrex Corporation supported by FEM modeling at Weidlinger Associates and the University of Strathclyde. The array was constructed by Materials Systems Inc. (MSI) using their proprietary injection-molded composite technology and was tested by UDI-Fugro. Materials characterization was conducted at the Royal Military College of Canada. The details of the final array design are described including the final composite microstructure, choice of composite filler, matching layer material and dicing pattern, and kerf filler. Array parameters achieved include 330 kHz center frequency, 245 kHz bandwidth, element acceptance angle from 62° at 250 kHz to 48° at 500 kHz, and sensitivity of -193 dB re 1V/uPa. FEM simulations showed excellent correspondence in predicting element electrical impedance