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Proceedings Paper

Comparison of signal extraction techniques in LDV signal processing
Author(s): Rajan Menon; L. Jenson; J. Buddhavarapu
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Paper Abstract

Accurate measurement of the velocity field and associated flow properties, using LDV, demands the use of an optimized signal processing system with the ability to extract signals from noisy photodetector output. Although, ostensibly, both auto-correlation and spectrum analysis techniques convey the same information, the unique nature of the Doppler signal provides a special situation where auto-correlation has certain advantages. The theoretical approach to examine the analysis techniques and the potential errors that can be caused by some simplifying assumptions are discussed. To overcome the limitations of the theoretical approach, results from both computer simulation and experimental measurements are provided. Special characteristics of the Doppler signal make the sampling process and the signal detection to be crucial to getting accurate measurements. It is shown that in the DFT approaches used partial fill of data block occurs resulting in a strong impact on the lowest measurable signal quality and the associated measurement accuracy. The ability of the auto- correlation approach to overcome these problems and the robustness of the processing scheme are discussed. In addition, the auto-correlation based processors (IFA 750 & 650) provide the ability to optimize the sampling rate for each burst and the system in real time to provide higher measurement rate, better accuracy and the ability to measure lower turbulence. These capabilities are borne out by results from actual measurements.

Paper Details

Date Published: 6 August 1993
PDF: 8 pages
Proc. SPIE 2052, Fifth International Conference on Laser Anemometry: Advances and Applications, (6 August 1993); doi: 10.1117/12.150524
Show Author Affiliations
Rajan Menon, TSI Inc. (United States)
L. Jenson, TSI Inc. (United States)
J. Buddhavarapu, TSI Inc. (United States)

Published in SPIE Proceedings Vol. 2052:
Fifth International Conference on Laser Anemometry: Advances and Applications
J. M. Bessem; R. Booij; H. W. H. E. Godefroy; P. J. de Groot; K. Krishna Prasad; F. F. M. de Mul; E. J. Nijhof, Editor(s)

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