Mutual Reference Technique for Array Calibration

Abstract

The resolving capability of a sonar system is governed by several key parameters such as aperture size, operating frequency, bandwidth of transmitted pulse, and noise level. The characteristics of the receiving transducers of a multiple-element array are typically assumed to be ideal and identical. In practice, each receiving transducer is unique in terms of functions and responses. Accurate signal detection has become increasingly important as high-performance sonar imaging continues to emphasize resolving capability. As a result, array calibration now plays an important role in data acquisition as well as overall system performance.

In the past, array calibration was performed in a relatively primitive manner by using one of the channels as the reference signal. The error characteristics of the reference channel can propagate through the entire calibration process and result in degradation of overall system performance. In this paper, we present a systematic mutual reference calibration procedure technique for multiple-element sonar arrays. This method provides a simple and systematic calibration procedure with superior accuracy and computational efficiency. The accuracy of the calibration procedure is optimized by a singular value decomposition process and the complex correction vector is constructed from the most significant eigenvector.

The presentation of this paper includes a complete system modeling procedure, theoretical analysis, algorithm implementation, and results from full-scale experiments with a Sonatech SAS-10 sonar array.