Signal-to-noise characteristics of photodiode array fourier transform spectrometers

1988 ◽  
Vol 95 (1-6) ◽  
pp. 323-324
Author(s):  
Roger A. Van Tassel ◽  
Wallace K. Wong
Keyword(s):  
Fourier Transform ◽  
Signal To Noise ◽  
Noise Characteristics ◽  
Photodiode Array

An automatic means to discriminate between earthquakes and quarry blasts

1990 ◽  
Vol 80 (6B) ◽  
pp. 2143-2160
Author(s):  
Michael A. H. Hedlin ◽  
J. Bernard Minster ◽  
John A. Orcutt
Keyword(s):  
Fourier Transform ◽  
Spectral Features ◽  
Single Event ◽  
Vertical Array ◽  
Signal To Noise ◽  
Spectral Character ◽  
Frequency Pattern ◽  
Time Frequency ◽  
Cepstral Analysis ◽  
Double Fourier Transform

Abstract In this article we discuss our efforts to use the NORESS array to discriminate between regional earthquakes and ripple-fired quarry blasts (events that involve a number of subexplosions closely grouped in space and time). The method we describe is an extension of the time versus frequency “pattern-based” discriminant proposed by Hedlin et al. (1989b). At the heart of the discriminant is the observation that ripple-fired events tend to give rise to coda dominated by prominent spectral features that are independent of time and periodic in frequency. This spectral character is generally absent from the coda produced by earthquakes and “single-event” explosions. The discriminant originally proposed by Hedlin et al. (1989b) used data collected at 250 sec−1 by single sensors in the 1987 NRDC network in Kazakhstan, U.S.S.R. We have found that despite the relatively low digitization rate provide by the NORESS array (40 sec−1) we have had good success in our efforts to discriminate between earthquakes and quarry blasts by stacking all vertical array channels to improve signal-to-noise ratios. We describe our efforts to automate the method, so that visual pattern recognition is not required, and to make it less susceptible to spurious time-independent spectral features not originating at the source. In essence, we compute a Fourier transform of the time-frequency matrix and examine the power levels representing energy that is periodic in frequency and independent of time. Since a double Fourier transform is involved, our method can be considered as an extension of “cepstral” analysis (Tribolet, 1979). We have found, however, that our approach is superior since it is cognizant of the time independence of the spectral features of interest. We use earthquakes to define what cepstral power is to be expected in the absence of ripple firing and search for events that violate this limit. The assessment of the likelihood that ripple firing occurred at the source is made automatically by the computer and is based on the extent to which the limit is violated.

scholarly journals On range super - resolution in a radar with many carriers. Simulation and experiment

2019 ◽  
pp. 24-29
Author(s):  
I. L. Nagornykh ◽  
N. D. Bazhenov
Keyword(s):  
Fourier Transform ◽  
Traditional Method ◽  
Super Resolution ◽  
Music Algorithm ◽  
Signal To Noise ◽  
Range Resolution ◽  
Probing Signal ◽  
Simulation And Experiment ◽  
The Fourier Transform ◽  
Research Show

The paper focuses on radar operation and the results of its simulation. The probing signal of the radar is a set of 16 orthogonal carriers. To determine the range in such radar, the MUSIC algorithm was applied, which relates to super - resolution methods. Findings of research show that the MUSIC algorithm makes it possible to increase the radar range resolution in the signal - to-noise 0-20 dB ratio by 4-8 times as compared with the traditional method based on the Fourier transform. The developed models were experimentally verified

Low-Frequency Photoacoustic Spectroscopy of Solids

1988 ◽  
Vol 42 (2) ◽  
pp. 289-292 ◽  
Author(s):  
J. C. Donini ◽  
K. H. Michaelian
Keyword(s):  
Fourier Transform ◽  
Carbon Black ◽  
Low Frequency ◽  
Far Infrared ◽  
Research Quality ◽  
Signal To Noise ◽  
Single Spectrum ◽  
Mid Infrared ◽  
Infrared Spectrometer ◽  
Computational Procedures

Research-quality far-infrared photoacoustic (PA) spectra are obtainable with a Fourier transform infrared spectrometer, the only changes with respect to conventional mid-infrared PA spectroscopy being the use of (1) a caesium iodide or polyethylene window on the PA cell, and (2) a mylar beamsplitter. Far-infrared PA spectra of several solids (bentonite, Fe+3-bentonite, and asbestos), in addition to the PA reference carbon black, have been recorded in this way. In order to improve signal-to-noise ratios in one of the spectra, we recorded ten interferograms under identical conditions; it was found that the average of the ten individually calculated spectra displays less noise and fewer spurious features than the spectrum obtained by first averaging the interferograms and then calculating a single spectrum. The results of this investigation demonstrate the feasibility of far-infrared PA spectroscopy, and illustrate that both experimental and computational procedures should be optimized in order to obtain the most satisfactory spectra.

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