An Octave Bandwidth Constant Beamwidth Underwater Receiving Array

摘要

A method for providing a constant beamwidth over an octave frequency bandwidth for an acoustical array is presented. This is accomplished by designing an array of the desired characteristics at lower band limit and a half scale model that will have the identical characteristics at twice that frequency. The outputs of these arrays are combined after filtering. The filter responses are derived by imposing the constant beamwidth constraints. Such an array was implemented to cover the octave 10 to 20 KHz. Two 5-element broadside arrays were combined but because of redundancy only 7 elements were required. Because of poor element frequency response and nonuniformity, the on-axis frequency response was not flat over the octave. However, the measured beamwidth was 20 plus or minus 1 degrees for a design value of 20.8 degrees. (Author)