A closed loop ML algorithm for phase aberration correction in phased array imaging systems. Part I : Algorithm synthesis and experimental results

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 44; no. 2; pp. 259 - 270
• Main Author: FORTES, J. M. P
• Format: Journal Article
• Language: English
• Published: New York, NY Institute of Electrical and Electronics Engineers 1997
• Subjects: Acoustic signal processing; Acoustical measurements and instrumentation; Acoustics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics; Closed loop; Circuit design; Feedback regulation; Phased array; Experimental study; Real time; Phase distortion; Algorithms; Signal processing; Medical imagery; Acoustic antenna; Maximum likelihood; Acoustic image
• ISSN: 0885-3010
• DOI: 10.1109/58.585111

This paper describes a new closed loop algorithm, based on the maximum likelihood theory, that corrects phase aberrations in phased array coherent imaging systems using phase estimates which are directly obtained from measured data (and not from estimated correlation functions). It has the advantage of estimating phase differences with respect to the same reference, and not phase differences between signals in adjacent array elements, eliminating the need to perform an integration to get the phase aberration profile. It allows for a real time implementation, in the sense that corrected data flows out of the circuit at the same rate that input data is fed into it. Being a closed loop algorithm, it is able to track time variations that may occur in the phase aberrations and, as in any phase lock loop circuit, it shows a trade-off between acquisition time and phase jitter.