Prof. Gabriel Thomas Profile

Prof. Gabriel Thomas

at Univ of Manitoba

SPIE Involvement:

Author

Publications (15)

Proceedings Article | 13 March 2006 Paper

Skin surface removal on breast microwave imagery using wavelet multiscale products

Daniel Flores-Tapia, Gabriel Thomas, Stephen Pistorius

Proceedings Volume 6143, 61433A (2006) https://doi.org/10.1117/12.659362

KEYWORDS: Wavelets, Skin, Reflection, Breast, Breast cancer, Cancer, Tissues, Microwave radiation, Detection and tracking algorithms, Stationary wavelet transform

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Proceedings Article | 16 May 2005 Paper

Generation of quasi-normal variables using discrete chaotic maps

Benjamin Flores, Berenice Verdin, Gabriel Thomas, Ali Ashtari

Proceedings Volume 5788, (2005) https://doi.org/10.1117/12.603962

KEYWORDS: Statistical analysis, Algorithms, Error analysis, Electroluminescence, Alternate lighting of surfaces, Radar, Radar sensor technology, Convolution, Visualization

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Proceedings Article | 12 August 2004 Paper

Resolution issues in the analysis of radar signals via Fourier approaches

Benjamin Flores, Hector Ochoa, Gabriel Thomas

Proceedings Volume 5410, (2004) https://doi.org/10.1117/12.537368

KEYWORDS: Radar, Doppler effect, Signal analyzers, Spectral resolution, Destructive interference, Signal processing, Electroluminescence, Optical resolution, Computer simulations, Image resolution

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Classical work in the field of high-resolution radar often assumes that an echo signal is made of a number of components that can be decomposed via Fourier analysis. Adjacent components are said to be resolved in the frequency domain if the intensity between them drops at least 3 decibels. This working definition is an extension of Lord Rayleigh's criterion for optical resolution. The problem with this approach is that whereas Rayleigh's criterion assumes signal incoherence, thus allowing for the addition of power components, a high-resolution radar signal is often the coherent sum of sinusoids, which implies voltage addition. The purpose of this paper is to discuss the consequences of using Rayleigh's criterion in the analysis of radar signals. Specifically, computer simulations using a complex signal are analyzed via the periodogram as the relative phase between the two components of the signal is allowed to change. The net effect introduced by this phase variation is to reduce or increase the spacing and intensity between two adjacent spectral peaks. These changes are due to constructive or destructive interference of spectral cross terms that cannot be ignored when attempting to resolve frequency components from one another. For instance, the simulations show that when using the averaged periodogram, the intensity in-between two adjacent components is above the -3 decibel threshold for a phase range of 1.2π radians, although the standard resolution criterion of c/2β is satisfied. Similar results are obtained when using a number of windows that are known to control sidelobe levels. Thus, the use of Rayleigh's criterion to define the resolution of a high-resolution radar system is technically inconsistent and undermines our ability to perform quantitative comparisons of target profiles, Doppler profiles and range-Doppler images. In this light, the authors promote the adoption of alternative criteria for judging resolution gains based on the norm of the signal in the (spatial) frequency domain.

Proceedings Article | 1 August 2002 Paper

Chaotic signals for wideband radar imaging

Benjamin Flores, Emmanuel Solis, Gabriel Thomas

Proceedings Volume 4727, (2002) https://doi.org/10.1117/12.478670

KEYWORDS: Frequency modulation, Fermium, Chaos, Signal processing, Doppler effect, Radar imaging, Stochastic processes, Electroluminescence, Modulation, Fractal analysis

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Proceedings Article | 20 November 2001 Paper

Time-frequency analysis using sidelobe apodization

Gabriel Thomas

Proceedings Volume 4474, (2001) https://doi.org/10.1117/12.448665

KEYWORDS: Apodization, Time-frequency analysis, Fourier transforms, Signal detection, Signal analyzers, Modulation, Computer engineering, Radar, Scintillation, Signal processing

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SPIE Journal Paper | 1 February 2001

Selective inverse synthetic aperture radar imaging of moving targets

Gabriel Thomas, Benjamin Flores, Salim Tariq

OE, Vol. 40, Issue 02, (February 2001) https://doi.org/10.1117/12.10.1117/1.1339205

KEYWORDS: Synthetic aperture radar, Fourier transforms, Filtering (signal processing), Statistical analysis, Optical filters, Seaborgium, Signal to noise ratio, Optical engineering, Radar, Binary data

Proceedings Article | 13 August 1999 Paper

SAR sidelobe apodization using parametric windows

Gabriel Thomas, Jae Sok Son, Benjamin Flores

Proceedings Volume 3721, (1999) https://doi.org/10.1117/12.357625

KEYWORDS: Apodization, Synthetic aperture radar, Signal attenuation, Fourier transforms, Image filtering, RGB color model, Electroluminescence, Image processing, Image resolution, Numerical analysis

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Proceedings Article | 14 October 1998 Paper

Time-varying filters for ISAR motion compensation

Gabriel Thomas, Benjamin Flores

Proceedings Volume 3462, (1998) https://doi.org/10.1117/12.326744

KEYWORDS: Radar, Fourier transforms, Seaborgium, Image processing, Optical filters, Time-frequency analysis, Binary data, Machine vision, Computer vision technology, Image filtering

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Proceedings Article | 24 September 1997 Paper

ISAR imaging of moving targets via the Gabor wavelet transform

Gabriel Thomas, Benjamin Flores, Ana Martinez

Proceedings Volume 3161, (1997) https://doi.org/10.1117/12.283948

KEYWORDS: Doppler effect, Wavelet transforms, Image processing, Electronic filtering, Fourier transforms, Distortion, Radar imaging, Wavelets, Image resolution, Signal processing

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Proceedings Article | 28 July 1997 Paper

Estimation of motion parameters by isolating scatterers using time-frequency filtering

Ke Liu, Gabriel Thomas, Sergio Cabrera

Proceedings Volume 3070, (1997) https://doi.org/10.1117/12.281582

KEYWORDS: Motion estimation, Electronic filtering, Signal to noise ratio, Time-frequency analysis, Motion models, Interference (communication), Image filtering, Super resolution, Error analysis, Computer simulations

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Proceedings Article | 5 November 1996 Paper

Evaluation of time-frequency filtering for SAR/ISAR motion compensation via instantaneous frequency estimators

Gabriel Thomas, Ke Liu, Sergio Cabrera, Benjamin Flores

Proceedings Volume 2845, (1996) https://doi.org/10.1117/12.257218

KEYWORDS: Signal to noise ratio, Electronic filtering, Time-frequency analysis, Image filtering, Autoregressive models, Motion estimation, Filtering (signal processing), Fourier transforms, Linear filtering, Motion models

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Proceedings Article | 10 June 1996 Paper

Selective motion compensation in ISAR imagery using time-frequency filtering

Gabriel Thomas, Sergio Cabrera, Benjamin Flores

Proceedings Volume 2757, (1996) https://doi.org/10.1117/12.242034

KEYWORDS: Image filtering, Fourier transforms, Time-frequency analysis, Resolution enhancement technologies, Electronic filtering, Image processing, Data modeling, Motion estimation, Super resolution, Synthetic aperture radar

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Proceedings Article | 18 August 1995 Paper

Signal separation and synthesis from modified superresolution short-time Fourier transforms

Gabriel Thomas, Sergio Cabrera

Proceedings Volume 2562, (1995) https://doi.org/10.1117/12.216967

KEYWORDS: Super resolution, Time-frequency analysis, Fourier transforms, Resolution enhancement technologies, Image processing, Radar imaging, Signal processing, Electronic filtering, Image resolution, Statistical analysis

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Proceedings Article | 9 June 1994 Paper

Application of one-dimensional adaptive extrapolation to improve resolution in range-Doppler imaging

Sergio Cabrera, Benjamin Flores, Gabriel Thomas, Javier Vega-Pineda

Proceedings Volume 2230, (1994) https://doi.org/10.1117/12.177200

KEYWORDS: Image resolution, Image processing, Raster graphics, Fourier transforms, Signal to noise ratio, Image acquisition, Radar, Synthetic aperture radar, Signal processing, Electroluminescence

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Proceedings Article | 1 November 1993 Paper

Evolutionary spectral estimation based on adaptive use of weighted norms

Sergio Cabrera, Benjamin Flores, Gabriel Thomas, Javier Vega-Pineda

Proceedings Volume 2027, (1993) https://doi.org/10.1117/12.160432

KEYWORDS: Autoregressive models, Fourier transforms, Time-frequency analysis, Stars, Yield improvement, Data modeling, Statistical analysis, Electroluminescence, Signal analyzers, Reflectivity

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Showing 5 of 15 publications

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