Waveform digitizer based lock in amplifier using GPU digital signal processing

2019 ◽  
Author(s):  
Alexandre Castonguay ◽  
Romain Deterre ◽  
Muneeb Khalid
Keyword(s):  
Signal Processing ◽  
Digital Signal Processing ◽  
Digital Signal ◽  
Lock In

Polarization Modulation Fourier Transform Infrared Spectroscopy with Digital Signal Processing: Comparison of Vibrational Circular Dichroism Methods

2001 ◽  
Vol 55 (11) ◽  
pp. 1435-1447 ◽  
Author(s):  
Jovencio Hilario ◽  
David Drapcho ◽  
Raul Curbelo ◽  
Timothy A. Keiderling
Keyword(s):  
Signal Processing ◽  
Circular Dichroism ◽  
Digital Signal Processing ◽  
Digital Signal ◽  
Vibrational Circular Dichroism ◽  
Polarization Modulation ◽  
Rapid Scan ◽  
Ft Ir ◽  
Lock In ◽  
Circular Dichroïsm

Digital signal processing (DSP) has been implemented in a step-scan FT-IR spectrometer in a modification that enables processing of high-frequency polarization modulation signals. In this work, direct comparison is made between vibrational circular dichroism (VCD) spectra measured on the same instrument, with the same samples, under the same conditions, using this new DSP method and a conventional rapid-scan technique (employing a lock-in amplifier for demodulation). In this initial test, both techniques generated high-quality VCD for solution phase, rigid chiral molecules such α-pinene and camphor. Noise and reproducibility of known spectral features, as well as enhancing signal measurability and discrimination, were used as criteria for the selection of optimal DSP measurement parameters. Both DSP and rapid-scan VCD methods produced qualitatively reasonable spectra for biologically related molecules such as poly-γ-benzyl-L-glutamate, poly-L-proline, and duplex RNA homopolymer. In most cases, the DSP method had a slight signal-to-noise advantage based on standard deviations of the noise trace data over the rapid-scan measurement, but the final results did depend on the details of the data collection and the phase correction methods inherent in both methods.

Step-Scanning Interferometer with Digital Signal Processing

1993 ◽  
Vol 47 (9) ◽  
pp. 1345-1349 ◽  
Author(s):  
Christopher J. Manning ◽  
Peter R. Griffiths
Keyword(s):  
Signal Processing ◽  
Digital Signal Processing ◽  
Digital Signal Processor ◽  
Modulation Frequency ◽  
Depth Profiling ◽  
Digital Signal ◽  
Scanning Interferometer ◽  
Ft Ir ◽  
Lock In ◽  
Signal Processor

A novel step-scan FT-IR spectrometer incorporating a digital signal processor for demodulation of the detector signal is described. The potential advantages of this method of signal processing are discussed and illustrated. The instrument is based on a commercial cube-corner interferometer which has been modified by replacement of the drive motor with a stepper motor-micrometer and piezoelectric transducer combination. The interferometer retardation is feedback controlled by a 486–50 personal computer, which also controls the digital signal processor and collects spectral data. More than one phase modulation frequency can be imposed simultaneously, allowing for a multiplex advantage in photoacoustic depth profiling. Digital signal processing allows for simultaneous demodulation of multiple frequencies which would normally require several lock-in amplifiers. Data that illustrate the feasibility of these concepts are presented. The suitability of this instrument for double-modulation step-scan FT-IR measurements such as polymer stretching and electrochemically modulated step-scan FT-IR is also discussed.

Method of estimation of hidden correlation of narrowband noise signals

2019 ◽  
pp. 34-39 ◽  
Author(s):  
E.I. Chernov ◽  
N.E. Sobolev ◽  
A.A. Bondarchuk ◽  
L.E. Aristarhova
Keyword(s):  
Signal Processing ◽  
Digital Signal Processing ◽  
New Technology ◽  
Digital Signal ◽  
Measuring Instruments ◽  
Central Frequency ◽  
Pearson Criterion ◽  
Useful Signal ◽  
Band Limited ◽  
Narrowband Noise

The concept of hidden correlation of noise signals is introduced. The existence of a hidden correlation between narrowband noise signals isolated simultaneously from broadband band-limited noise is theoretically proved. A method for estimating the latent correlation of narrowband noise signals has been developed and experimentally investigated. As a result of the experiment, where a time frag ent of band-limited noise, the basis of which is shot noise, is used as the studied signal, it is established: when applying the Pearson criterion, there is practically no correlation between the signal at the Central frequency and the sum of signals at mirror frequencies; when applying the proposed method for the analysis of the same signals, a strong hidden correlation is found. The proposed method is useful for researchers, engineers and metrologists engaged in digital signal processing, as well as developers of measuring instruments using a new technology for isolating a useful signal from noise – the method of mirror noise images.

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