Analysis of two methods of calibration of an ultrasonic antenna array mounted on a prism

The image quality of the reflectors, restored using digital antenna focusing technology or phased array technology, depends on the accuracy of determining such parameters of the prism as the boom, path, longitudinal wave velocity and angle of inclination. These parameters do not always correspond to the passport parameters, both due to the accuracy of the manufacture of prisms and the placement of antenna array elements in the housing, and due to the wear of the prisms during operation. The article discusses two types of calibration of an antenna array mounted on a prism: variational and simplified. The principle of variational calibration is to minimize the objective function describing the difference between the echo signals measured by the antenna array from the side cylindrical holes, for example, in the ISO 19675 PAUT BLOCK sample and the calculated echo signals. Simplified calibration is based on the analysis of the arrival time of echo signals from the prism sole, which allows you to estimate the path and angle of inclination of the prism, knowing the velocity of the longitudinal wave in the prism. The operation of the variational calibration was tested on echo signals calculated in the CIVA program to demonstrate the gully structure of the target function. An assessment of the required accuracy of determining all four parameters of the prism is made. The results of calibration of the antenna array on four prisms are presented and the results of variational and simplified calibrations are verified. The accuracy of determining the parameters of the prism when using variational calibration is more than twice as good as the results obtained with simplified calibration. However, the time required for calculations with variational calibration is more than three orders of magnitude longer than for simplified calibration.