Mr. Germano S. Fonseca Profile

Germano S. Fonseca

at Ctr Tecnologico do Exercito

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Proceedings Article | 12 April 2021 Poster + Presentation + Paper

Linear models for SWIR surface spectra from the ECOSTRESS library

Germano Fonseca, Augusto Cezar dos Santos, Leonardo de Sá, José Gabriel R. Gomes

Proceedings Volume 11727, 117271J (2021) https://doi.org/10.1117/12.2587752

KEYWORDS: Short wave infrared radiation, Systems modeling, Imaging systems, Hyperspectral imaging, Error analysis, Data modeling, Visible radiation, Statistical modeling, Spectrometers, Shortwaves

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Hyperspectral imaging systems act as imaging spectrometers, acquiring dozens or hundreds of equally spaced spectral channels, thus leading to high complexity setups, low acquisition speed, and a large amount of data. In order to optimize the number of acquisition channels, and to mitigate these problems in shortwave infrared (SWIR) hyperspectral imaging systems, one must extend to the SWIR range the analysis and characterization methods that are available, in the literature, for the visible spectrum. To that end, this work focuses on the SWIR surface spectral reflectance (SSR) of possible objects that may be present in the scene, by analyzing an empirical SSR library that includes the SWIR range, as the ECOSTRESS spectral library. To the best of our knowledge, this is the first report of SWIR SSR data analysis in this library. The main goal of this paper is to investigate the approximation of data samples in this library by two linear models, namely truncated Fourier Series and principal components, both with less than a dozen basis vectors. This corresponds to significant dimension reduction in comparison to the number of acquisition channels, which lies in the several hundreds in the ECOSTRESS library. To validate the analysis and assess the quality of the reconstructed spectra, root mean squared error and goodness-of-fit coefficient(GFC) metrics are applied. An `accurate' to `excellent' fit with GFC median ranging between 0.995 and 0.9999 is obtained when reconstructing the signals with three to five principal components, and greater than 0.995 with three to five Fourier series terms.

Proceedings Article | 20 May 2016 Paper

Extraction of static parameters to extend the EKV model to cryogenic temperatures

Germano Fonseca, Leonardo de Sá, Antonio Mesquita

Proceedings Volume 9819, 98192B (2016) https://doi.org/10.1117/12.2219734

KEYWORDS: Cryogenics, Transistors, Device simulation, Temperature metrology, Thermal modeling, Infrared radiation, CMOS technology, Instrument modeling, Standards development, Molybdenum

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The electric simulation models of CMOS devices provided by the foundries are valid at the standard temperature range of -55 to 125°C. These models are not suitable to the design of circuits intended to operate at cryogenic temperatures as is the case of cooled infrared readout circuits. To generate a library of CMOS electric simulation models valid at cryogenic temperatures, the characterization of wide and long CMOS transistors are investigated. The EKV2.6 model, which is an industry-standard compact simulation model for CMOS transistors, is used in this characterization. Due to its relatively small number of parameters the EKV2.6 model is well suited to the parameter extraction procedures when not disposing of an expensive automated parameter extraction system. It is shown that to provide an appropriate IV-characteristic fit to cryogenic temperature range it is sufficient to extract only five parameters - threshold voltage VT0, body effect GAMMA, Fermi potential PHI, transconductance factor KP, and the vertical characteristic field for mobility reduction E0. The proposed approach is tested in a standard 0.35μm/3.3V CMOS technology, employing extraction procedures recommended in the literature. Simulations are made with a BSIM3V3 standard library provided by the foundry changing the temperature parameter and with the generated library. The results are compared with the measurements. As expected, the simulations made with the generated library show a best agreement with the performed measurements at 77K than the simulations with the BSIM3V3 model. The proposed methodology is shown to be particularly effective above strong freeze-out temperature.

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