Performance verification testing of a high-resolution side-looking sonar

We discuss the design and present field-test results for a 2-meter-long high-frequency multi-beam side-looking sonar. We tested this sonar in shallow water from a pier near Santa Barbara, California, using a rail mechanism developed especially for these tests. The principal goal of the testing was to demonstrate the sonar achieved its 3-inch along-track (azimuthal) resolution at an across-track range of 70 meters. To accomplish this goal, we constructed a target grid composed of a number of strong, point-like reflectors and deployed it at several ranges during the tests. We developed special-purpose beamforming and control software to produce high-beam density images. We discuss the test procedures and results as well as the design and performance features of the sonar. The acoustic targets and rail mechanism we used in the tests have some interesting design and performance characteristics, which we describe. We provide details of the beamforming and signal processing utilized as well as beamformed images that demonstrate the high resolution and phase linearity of the sonar array.