Behind Acoustic Doppler Current Profiler: Narrowband Volume Backscattering Signal Model, Analysis and Estimation
Blekinge Institute of Technology, Department of Telecommunications and Signal Processing1999 (English)Report (Other academic)
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.
Fysikalisk meknism kring akustisk Doppler volym-återspridning har teoretiskt analyserats.
Place, publisher, year, edition, pages
Blekinge Tekniska Högskola Forskningsrapport, ISSN 1103-1581 ; 15
ADCP, current measurement, volume backscattering, Doppler effect, non-stationary spectral analysis, wavelet shrinkage, TVAR
IdentifiersURN: urn:nbn:se:bth-00129Local ID: oai:bth.se:forskinfo69BEE30C1FCFCEA6C12568A3002CAC17OAI: oai:DiVA.org:bth-00129DiVA: diva2:837932