Digital Signal Processing for Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy

1997 ◽  
Vol 51 (4) ◽  
pp. 453-460 ◽  
Author(s):  
David L. Drapcho ◽  
Raul Curbelo ◽  
Eric Y. Jiang ◽  
Richard A. Crocombe ◽  
William J. McCarthy
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Digital Signal Processing ◽  
Phase Modulation ◽  
Modulation Frequency ◽  
Digital Signal ◽  
Sampling Depth ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy ◽  
Additional Hardware

A software-based digital signal processing (DSP) method using the data system processor has been developed to demodulate the photoacoustic responses of a sample to the fundamental phase modulation frequency and its harmonic frequencies (up to the ninth harmonic) in step-scan FT-IR photoacoustic measurements, without the use of any additional hardware. The DSP algorithm and its sampling depth multiplexing advantages are compared to conventional hardware demodulation. Comparison of results from the DSP method to those from hardware demodulators are shown at both the phase modulation frequency and the harmonics, and application of the DSP method to step-scan photoacoustic measurements with phase modulation is discussed as it applies to obtaining depth profile information in heterogeneous materials.

Analysis of Cheese Using Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy

2000 ◽  
Vol 54 (4) ◽  
pp. 595-600 ◽  
Author(s):  
Joseph Irudayaraj ◽  
Hong Yang
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Photoacoustic Spectroscopy ◽  
Depth Profiling ◽  
Cheddar Cheese ◽  
Digital Signal ◽  
Fourier Transform Infrared ◽  
Intact Sample ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy

The potential of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) for examination of food and the package was demonstrated. Full-fat cheddar cheese slices wrapped in polymer package were chosen as the food sample for analysis. Photoacoustic spectroscopy (PAS) in conjunction with the step-scan and digital signal processing (DSP) function was used to perform depth-profiling studies of the intact sample and package. Well-separated PAS bands of fat and protein were obtained in the spectra of cheddar cheese samples with minimum sample preparation. Cheese samples were kept in a dessicator overnight to minimize the effect of moisture on the PAS spectra. Depth profiling study of the cheese polymer package indicated that there is a diffusion of cheese components into the package during storage.

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.

Depth Profile Study of Large-Sized Coal Samples by Fourier Transform Infrared Photoacoustic Spectroscopy

1986 ◽  
Vol 40 (2) ◽  
pp. 214-217 ◽  
Author(s):  
Tiziana Zerlia
Keyword(s):  
Fourier Transform ◽  
Depth Profile ◽  
Photoacoustic Spectroscopy ◽  
Modulation Frequency ◽  
Fourier Transform Infrared ◽  
Qualitative Description ◽  
Difference Spectra ◽  
Compositional Depth Profile ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy

A multidisciplinary approach is demonstrated to elucidate coal weathering at a molecular level. Fourier Transform Infrared Photoacoustic Spectroscopy (FT-IR/PAS) provides a technique for a compositional depth profile of coal by simply varying the modulation frequency (mirror velocity) of the light impinging upon the solid surface. In order that the potential of this technique in this field could be evaluated, large-sized coal samples were examined. The PA difference spectra obtained from the spectra taken at different modulation frequencies (i.e., different depths), on a sample aged in air, demonstrate the appearance of negative features in the CH infrared absorption which are indicative of a coal alteration. Therefore, different coal layers can be distinguished by FT-IR/PAS. The application of the same technique to the study of a coal sample heated in air at 200°C allows the detection of different oxidation mechanisms operating inside and outside the coal. Although quantitative results are difficult to obtain, the technique can be successfully proposed for a qualitative description of coal weathering.

scholarly journals Digital signal processing in telecommunications based on parametric discrete Fourier transform

2019 ◽  
Vol 30 ◽  
pp. 04010 ◽  
Author(s):  
Olga Ponomareva ◽  
Alexey Ponomarev ◽  
Natalya Smirnova
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Digital Signal Processing ◽  
Discrete Fourier Transform ◽  
Digital Signal ◽  
Discrete Transformation ◽  
Stochastic Properties

A generalization of the discrete Fourier transform in the form of a parametric discrete Fourier transform is proposed. The analytical and stochastic properties of the introduced discrete transformation are investigated. An example of the application of the parametric discrete Fourier transform in telecommunications is given - a generalization of the well-known Herzel algorithm

Classification of Women's Voices Using Fast Fourier Transform (FFT) Method

2021 ◽  
Vol 10 (1) ◽  
pp. 59
Author(s):  
Made Sri Ayu Apsari ◽  
I Made Widiartha
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Digital Signal Processing ◽  
Fast Fourier Transform ◽  
Digital Signal ◽  
Women's Voices ◽  
Mezzo Soprano

Everyone has a different kind of voice. Based on gender, voice type is divided into six parts, namely soprano, mezzo soprano, and alto for women; and tenor, baritone, and bass in men. Each type of sound has a different range and with different frequencies. This study classified the type of voice in women using the Fast Fourier Transform (FFT) method by recording the voices of each user which would then be processed using the FFT method to obtain the appropriate sound range. This research got results with an accuracy of up to 80%.The results obtained from this study are quite appropriate and it is proven that the FFT method can be used in digital signal processing.

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