Behind Acoustic Doppler Current Profiler - Narrowband Volume Backscattering Signal Model, Analysis and Estimation

Document type: Researchreports
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Author(s): Xiao-Jiao Tao, Ingvar Claesson, Nedelko Grbic, Mikael Åsman
Title: Behind Acoustic Doppler Current Profiler - Narrowband Volume Backscattering Signal Model, Analysis and Estimation
Series: Research Report
Year: 1999
Issue: 15
ISSN: 1103-1581
Organization: Blekinge Institute of Technology
Department: Department of Telecommunications and Signal Processing (Institutionen för telekommunikation och signalbehandling)
Department of Telecommunications and Signal Processing S-372 25 Ronneby
+46 455 780 00
Authors e-mail: xjt@its.hk-r.se
Language: English
Abstract: This report examines the statistical properties of the narrowband Doppler volume backscattering process and discusses its spectral centroid estimation problem. After clarifying the mechanism of both the finite duration Doppler effect and the continuously space-shifted integration process, the first two order time-varying statistics under a more general assumption, i.e. von Mises distribution, of random phase are derived. The generalization permits nonuniform phase tendency, which occurs in layered medium scattering. Based on the locally stationary process model, the evolutionary spectrum of the signal is derived where the variation of the backscattering strength enters as an amplitude modulation. On the contrary, the variation of the random phase distribution acts as both the amplitude modulation and the frequency modulation. The observability and the estimation of the average flow speed are discussed. It is shown that even under the homogeneous condition, the spectral centroid does not coincide with the aver
age flow speed. Finally, a semiparametric spectral centroid estimation method, which simply contains an AR(2) model with its time-varying coefficients adapted by a wavelet shrinkage is proposed.
Summary in Swedish: Fysikalisk meknism kring akustisk Doppler volym-återspridning har teoretiskt analyserats.
Subject: Signal Processing\Hydro-Acoustics
Keywords: ADCP, current measurement, volume backscattering, Doppler effect, non-stationary spectral analysis, wavelet shrinkage, TVAR
URN: urn:nbn:se:bth-00129
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