Coded excitation, digitising ultrasound acquisition

Coded excitation has emerged as a powerful approach for improving ultrasonic signal acquisition in challenging measurement environments. By replacing conventional short-duration pulsed excitation with longer coded waveforms and pulse-compression processing, significant improvements in signal-to-noise ratio (SNR), channel isolation, and acquisition efficiency can be achieved. However, comparison of reported performance improvements remains difficult because published studies frequently employ inconsistent terminology and performance metrics. This paper reviews the principles of coded excitation for ultrasonic inspection and monitoring applications, discussing phase, frequency and amplitude modulation approaches. Key benefits including SNR enhancement, multi-channel operation and hardware simplification are examined together with practical limitations arising from code imperfections, hardware imperfections and motion-induced distortions. A set of normalised performance metrics is proposed to facilitate objective comparison between coding schemes. Emphasis is placed on transmitted energy, acquisition duration, peak-to-sidelobe ratio and cross-correlation performance. Practical recommendations are provided for reporting coded excitation performance in non-destructive testing applications.