Spectral correlation in ultrasonic pulse echo signal processing

The effects of using spectral correlation in a maximum-likelihood estimator (MLE) for backscattered energy corresponding to coherent reflectors embedded in media of microstructure scatterers is considered. The spectral autocorrelation (SAC) function is analyzed for various scatterer configurations b...

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Bibliographic Details
Published in:IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 1993-07, Vol.40 (4), p.330-337
Main Authors: Donohue, K.D., Bressler, J.M., Varghese, T., Bilgutay, N.M.
Format: Article
Language:English
Subjects:
Acoustic signal processing
Acoustics
Adaptive filters
Amplitude estimation
Autocorrelation
Exact sciences and technology
Frequency
Fundamental areas of phenomenology (including applications)
Grain size
Maximum likelihood estimation
Microstructure
Parameter estimation
Physics
Scattering
Signal processing
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Summary:The effects of using spectral correlation in a maximum-likelihood estimator (MLE) for backscattered energy corresponding to coherent reflectors embedded in media of microstructure scatterers is considered. The spectral autocorrelation (SAC) function is analyzed for various scatterer configurations based on the regularity of the interspacing distance between scatterers. It is shown that increased regularity gives rise to significant spectral correlation, whereas uniform distribution of scatters throughout a resolution cell results in no significant correlation between spectral components. This implies that when a true uniform distribution for the effective scatterers exists, the power spectral density (PSD) is sufficient to characterize their echoes. However, as the microstructure scatterer distribution becomes more regular, SAC terms become more significant. MLE results for 15 A-scans from stainless steel specimens with three different grain sizes indicate an average 6-dB signal-to-noise ratio (SNR) improvement in the coherent scatterer (flat-bottom hole) echo intensities for estimators using the SAC characterization as opposed to the PSD characterization.< >
ISSN:0885-3010
1525-8955
DOI:10.1109/58.251281