Prof. Griff L. Bilbro Profile

Prof. Griff L. Bilbro

Professor at North Carolina State Univ

SPIE Involvement:

Author

Proceedings Article | 12 February 2009 Paper

Predicting the performance of a power amplifier using large-signal circuit simulations of an AlGaN/GaN HFET model

Griff Bilbro, Danqiong Hou, Hong Yin, Robert Trew

Proceedings Volume 7216, 721603 (2009) https://doi.org/10.1117/12.803348

KEYWORDS: Instrument modeling, Gallium nitride, Device simulation, Amplifiers, Performance modeling, Microwave radiation, Physics, Resistance, Heterojunctions, Measurement devices

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We have quantitatively modeled the conduction current and charge storage of an HFET in terms its physical dimensions and material properties. For DC or small-signal RF operation, no adjustable parameters are necessary to predict the terminal characteristics of the device. Linear performance measures such as small-signal gain and input admittance can be predicted directly from the geometric structure and material properties assumed for the device design. We have validated our model at low-frequency against experimental I-V measurements and against two-dimensional device simulations. We discuss our recent extension of our model to include a larger class of electron velocity-field curves. We also discuss the recent reformulation of our model to facilitate its implementation in commercial large-signal high-frequency circuit simulators. Large signal RF operation is more complex. First, the highest CW microwave power is fundamentally bounded by a brief, reversible channel breakdown in each RF cycle. Second, the highest experimental measurements of efficiency, power, or linearity always require harmonic load pull and possibly also harmonic source pull. Presently, our model accounts for these facts with an adjustable breakdown voltage and with adjustable load impedances and source impedances for the fundamental frequency and its harmonics. This has allowed us to validate our model for large signal RF conditions by simultaneously fitting experimental measurements of output power, gain, and power added efficiency of real devices. We show that the resulting model can be used to compare alternative device designs in terms of their large signal performance, such as their output power at 1dB gain compression or their third order intercept points. In addition, the model provides insight into new device physics features enabled by the unprecedented current and voltage levels of AlGaN/GaN HFETs, including non-ohmic resistance in the source access regions and partial depletion of the 2DEG in the drain access region.

Proceedings Article | 6 February 2008 Paper

Reliability modeling of high voltage AlGaN/GaN and GaAs field-effect transistors

R. Trew, Y. Liu, W. Kuang, G. Bilbro

Proceedings Volume 6894, 68941H (2008) https://doi.org/10.1117/12.764958

KEYWORDS: Reliability, Gallium arsenide, Data modeling, Electrodes, Semiconductors, Field effect transistors, Amplifiers, Transistors, Device simulation, Ka band

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SPIE Journal Paper | 1 July 2002

Demosaicking methods for Bayer color arrays

Rajeev Ramanath, Wesley Snyder, Griff Bilbro, William Sander

JEI, Vol. 11, Issue 03, (July 2002) https://doi.org/10.1117/12.10.1117/1.1484495

KEYWORDS: Image filtering, Image processing, Digital filtering, Cameras, RGB color model, Optical filters, Error analysis, Spatial frequencies, Evolutionary algorithms, Statistical analysis

Proceedings Article | 25 April 1997 Paper

Optimal interpolation for medical images using MAP method

Cliff Wang, Wesley Snyder, Griff Bilbro, Peter Santago, David Honea

Proceedings Volume 3034, (1997) https://doi.org/10.1117/12.274111

KEYWORDS: Image processing, Image resolution, Medical imaging, Image restoration, Image analysis, Annealing, Evolutionary algorithms, Reconstruction algorithms, Thermography, Point spread functions

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Proceedings Article | 16 April 1996 Paper

Performance evaluation of the filtered back projection reconstruction and the iterative ML reconstruction for PET images

Cliff Wang, Wesley Snyder, Griff Bilbro, Peter Santago

Proceedings Volume 2710, (1996) https://doi.org/10.1117/12.237995

KEYWORDS: Reconstruction algorithms, Image filtering, Positron emission tomography, Image quality, Tomography, Statistical analysis, Image restoration, Data modeling, Iterative methods, Scanners

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Proceedings Article | 30 June 1994 Paper

Recovering resolution and reducing noise in basis images via optimization methods using physical models

Stephen Garnier, Griff Bilbro, Wesley Snyder

Proceedings Volume 2304, (1994) https://doi.org/10.1117/12.179228

KEYWORDS: Magnetic resonance imaging, Nonlinear optics, Smoothing, Image fusion, Data modeling, Optimization (mathematics), Tissues, Interference (communication), Image resolution, Data acquisition

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Proceedings Article | 1 March 1994 Paper

Stochastic search

Griff Bilbro

Proceedings Volume 10277, 1027703 (1994) https://doi.org/10.1117/12.171192

KEYWORDS: Stochastic processes

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Proceedings Article | 29 October 1993 Paper

Fast stochastic global optimization

Griff Bilbro

Proceedings Volume 2032, (1993) https://doi.org/10.1117/12.162050

KEYWORDS: Stochastic processes, Optimization (mathematics), Algorithms, Signal processing, Algorithm development, Detection and tracking algorithms, Astatine, Computer engineering, Computer simulations, Differential equations

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Proceedings Article | 10 June 1993 Paper

Magnetic resonance image analysis

Stephen Garnier, Griff Bilbro, James Gault, Wesley Snyder, Youn-Sik Han

Proceedings Volume 1904, (1993) https://doi.org/10.1117/12.146698

KEYWORDS: Magnetic resonance imaging, Tissues, Data modeling, Image restoration, Data acquisition, Image processing, Magnetism, Interference (communication), Image analysis, Mathematical modeling

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Proceedings Article | 10 June 1993 Paper

Optimum displacement estimates using mean field annealing

Ikhlas Abdelqader, Sarah Rajala, Griff Bilbro, Wesley Snyder

Proceedings Volume 1904, (1993) https://doi.org/10.1117/12.146685

KEYWORDS: Annealing, Motion models, Motion estimation, Algorithm development, Interference (communication), Medicine, Magnetism, Magnetic resonance imaging, Heart, Blood

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Proceedings Article | 16 December 1992 Paper

Provably convergent inhomogeneous genetic annealing algorithm

Griff Bilbro, Jue Hall, Lawrence Ray

Proceedings Volume 1766, (1992) https://doi.org/10.1117/12.130816

KEYWORDS: Annealing, Genetics, Algorithms, Image processing, Signal processing, Stochastic processes, Quantization, Genetic algorithms, Image compression, Optimization (mathematics)

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Proceedings Article | 16 December 1992 Paper

Solution of the recirculant multilayer graph problem using compensated simulated annealing

Wesley Snyder, Terri Johnson, David Herrington, Griff Bilbro

Proceedings Volume 1766, (1992) https://doi.org/10.1117/12.130851

KEYWORDS: Algorithms, Stochastic processes, Image processing, Signal processing, Arteries, Ultrasonography, Sensors, Medical imaging, Optimization (mathematics), Medicine

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Proceedings Article | 1 October 1991 Paper

General method for accelerating simulated annealing algorithms for Bayesian image restoration

Griff Bilbro

Proceedings Volume 1569, (1991) https://doi.org/10.1117/12.48369

KEYWORDS: Stochastic processes, Algorithms, Image processing, Image restoration, Annealing, Signal processing, Machine vision, Computer vision technology, Process modeling, Signal to noise ratio

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Showing 5 of 13 publications

Conference Committee Involvement (1)

Neural and Stochastic Methods in Image and Signal Processing II

12 July 1993 | San Diego, CA, United States

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