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Laser Doppler Signal Denoising Based on Wavelet Packet Thresholding Method
摘要： In laser Doppler velocimeter (LDV), calculation precision of Doppler shift is affected by noise contained in Doppler signal. In order to restrain the noise interference and improve the precision of signal processing, wavelet packet threshold denoising methods are proposed. Based on the analysis of Doppler signal, appropriate threshold function and decomposition layer number are selected. Heursure, sqtwolog, rigrsure, and minimaxi rules are adopted to get the thresholds. Processing results indicate that signal-to-noise ratio (SNR) and root mean square error (RMSE) of simulated signals with original SNR of 0 dB, 5 dB, and 10 dB in both low- and high-frequency ranges are significantly improved by wavelet packet threshold denoising. A double-beam and double-scattering LDV system is built in our laboratory. For measured signals obtained from the experimental system, the minimum relative error of denoised signal is only 0.079% (using minimaxi rule). The denoised waveforms of simulated and experimental signals are much more smooth and clear than that of original signals. Generally speaking, denoising effects of minimaxi and saqtwolog rules are better than those of heursure and rigrsure rules. As shown in the processing and analysis of simulated and experimental signals, denoising methods based on wavelet packet threshold have ability to depress the noise in laser Doppler signal and improve the precision of signal processing. Owing to its effectiveness and practicability, wavelet packet threshold denoising is a practical method for LDV signal processing.
关键词： wavelet packet threshold denoising,laser Doppler velocimeter,signal-to-noise ratio,double-beam and double-scattering LDV system,root mean square error
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) - Auckland, New Zealand (2019.5.20-2019.5.23)] 2019 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) - Scanning Double-Beam Laser Interferometer with Loop-Back Compensation and Phase Stabilization
摘要： An accurate characterization of piezoelectric films is essential for their usage in various types of MEMS sensors and actuators. This paper presents a novel scanning double-beam laser interferometer (DBLI) to measure the thickness piezoelectric coefficient with a high accuracy. Compared to previous DBLI solutions, we employ a closed-loop phase shift compensation via an electro-optical modulator to stabilize the random phase drift as well as to compensate the harmonic sample-induced phase shift. As a consequence, the setup robustness is enhanced and the measured displacement is no more sensitive to sample reflectivity or source and detector signal gains, which allows to use the DBLI as scanning.
关键词： double-beam,laser scanning interferometry,phase compensation
更新于2025-09-12 10:27:22
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Design of a Simple UV Double Beam Spectrophotometer Detector Based on a High Gain Trans Impedance Operational Amplifiers for RNA Measurement
摘要： In this work a simple double beam spectropho-tometer detector for the nucleic acid detection has been designed. The developed system contains photodiodes as a sensor, logarithamatic transimpedance amplifier circuit and filter circuit.The developed prototype design accuracy is validated by running a RNA sample and the result shows that our simplified developed setup detects the present of RNA in the sample.
关键词： Photodiode,Trans impedance amplifier,RNA,double beam
更新于2025-09-09 09:28:46