Method to determine far-field beampattern of long from subarray beampattern measurements
* Presenting author
Beampattern measurement is essential to verify the performance of array sonar. However, the classic problem encountered in beampattern measurement of arrays is that the far-field conditions for reaching the plane wave are limited due to reasons such as the measurement space. We aim to measure the beampattern of the array in a limited space and to evaluate the performance through the -3dB beam width. Therefore, we propose a method to measure the beampattern of discrete line array in limited space. The proposed method is based on the sub-array method. A discrete line array whose measurement space does not satisfy the far-field condition is divided into several sub-arrays satisfying the far-field condition, and the beampattern of the line array is derived through the beampattern for the sub-array. The proposed method was verified by simulation and we performed a measurement experiment on a line array of 256 elements with a design frequency of 455 kHz. This method can measure the beampattern of the line array simply as compared with the method of converting the beampattern obtained from the measurement data in the near-field to the far-field.