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Electrical and Computer Engineering

Brigham Young University

1995

Articles 1 - 9 of 9

Full-Text Articles in Engineering

A Massively Parallel Computation Strategy For Fdtd: Time And Space Parallelism Applied To Electromagnetics Problems, Michael A. Jensen, Amir Fijany, Yahya Rahmat-Samii, Jacob Barhen Dec 1995

A Massively Parallel Computation Strategy For Fdtd: Time And Space Parallelism Applied To Electromagnetics Problems, Michael A. Jensen, Amir Fijany, Yahya Rahmat-Samii, Jacob Barhen

Faculty Publications

We present a novel strategy for incorporating massive parallelism into the solution of Maxwell's equations using finite-difference time-domain methods. In a departure from previous techniques wherein spatial parallelism is used, our approach exploits massive temporal parallelism by computing all of the time steps in parallel. Furthermore, in contrast to other methods which appear to concentrate on explicit schemes such as Yee's (1966) algorithm, our strategy uses the implicit Crank-Nicolson technique which provides superior numerical properties. We show that the use of temporal parallelism results in algorithms which offer a massive degree of coarse grain parallelism with minimum communication and synchronization …

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Integrating Reconstructed Scatterometer And Advanced Very High Resolution Radiometer Data For Tropical Forest Inventory, David G. Long, Perry J. Hardin Nov 1995

Integrating Reconstructed Scatterometer And Advanced Very High Resolution Radiometer Data For Tropical Forest Inventory, David G. Long, Perry J. Hardin

Faculty Publications

A scientific effort is currently underway to assess tropical forest degradation and its potential impact on Earth's climate. Because of the large continental regions involved, Advanced Very High Resolution Radiometer (AVHRR) imagery and its derivative vegetation index products with resolutions between 1 and 12 km are typically used to inventory the Earth's equatorial vegetation. Archival AVHRR imagery is also used to obtain a temporal baseline of historical forest extent. Recently however, 50-km Seasat-A Scatterometer (SASS) Ku-band imagery (acquired in 1978) has been reconstructed to = 4-km resolution, making it a supplement to AVHRR imagery for historical vegetation assessment. In order …

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A Pixel Scale Digital-To-Analog Converter Array For Liquid Crystal On Vlsi Displays, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Thomsen Sep 1995

A Pixel Scale Digital-To-Analog Converter Array For Liquid Crystal On Vlsi Displays, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Thomsen

Faculty Publications

A pixel scale digital to analog converter and driver for liquid crystal (LC) cells is presented. The circuit is a compact CMOS logic gate that sums pulse density modulation (pdm) signals. Low pass filtering of the pdm signal is 'done by the LC material. The circuit is suitable to implement large arrays of converters as, for example, in display applications. It is applicable in LC on silicon displays where gray scale data are stored and converted at each pixel site. Advantages over the commonly used active matrix technology include the removal of all analog circuitry, no need for refresh, reduced …

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Electromagnetic Boundary Conditions And Differential Forms, Karl F. Warnick, Richard H. Selfridge, David V. Arnold Aug 1995

Electromagnetic Boundary Conditions And Differential Forms, Karl F. Warnick, Richard H. Selfridge, David V. Arnold

Faculty Publications

A new representation for electromagnetic boundary conditions involving a boundary projection operator defined using the interior and exterior products of the calculus of differential forms is developed. This operator expresses boundary conditions for fields represented by differential forms of arbitrary degree. With vector analysis, the field intensity boundary conditions require the cross product, whereas the flux boundary conditions use the inner product. With differential forms, the field intensity and flux density boundary conditions are expressed using a single operator. This boundary projection operator is readily applied in practice, so that this work extends the utility of the calculus of differential …

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Liquid Crystal-On-Silicon Implementation Of The Partial Pixel Three-Dimensional Display Architecture, M. W. Jones, Gregory P. Nordin, M. Friends, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka Jul 1995

Liquid Crystal-On-Silicon Implementation Of The Partial Pixel Three-Dimensional Display Architecture, M. W. Jones, Gregory P. Nordin, M. Friends, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka

Faculty Publications

We report the implementation of a liquid crystal-on-silicon, three-dimensional 13-D2 diffractive display based on the partial pixel architecture. The display generates multiple stereoscopic images that are perceived as a static 3-D scene with one-dimensional motion parallax in a manner that is functionally equivalent to a holographic stereogram. The images are created with diffraction gratings formed in a thin liquid crystal layer by fringing electric fields from transparent indium tin oxide interdigitated electrodes. The electrodes are controlled by an external drive signal that permits the 3-D scene to be turned on and off. The display has a contrast ratio of 5.8, …

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Real-Time Three-Dimensional Display Based On The Partial Pixel Architecture, Gregory P. Nordin, M. W. Jones, S. T. Kowel, J. H. Kulick, R. G. Lindquist Jun 1995

Real-Time Three-Dimensional Display Based On The Partial Pixel Architecture, Gregory P. Nordin, M. W. Jones, S. T. Kowel, J. H. Kulick, R. G. Lindquist

Faculty Publications

We previously reported several static three-dimensional (3-D) display implementations of the partial pixel architecture [J. Opt. Soc. Am. A 12, 73 (1995)]. We report herein our f irst real-time 3-D display based on this architecture. The display is functionally equivalent to a real-time holographic stereogram. It is autostereoscopic and provides horizontal motion parallax. The display device is composed of a diffractive optical element (fabricated with standard photolithographic techniques) and a separate conventional liquidcrystal display. The display has been used to play back a precomputed animated 3-D scene at video frame rates using a standard VGA video output.

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Pulse Width Modulation Drive Technique For High Resolution Liquid Crystal Gratings, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Thomsen Mar 1995

Pulse Width Modulation Drive Technique For High Resolution Liquid Crystal Gratings, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Thomsen

Faculty Publications

We report the use of a pulse-width modulation drive technique for high-resolution liquid-crystal gratings and show how the grating diffraction efficiency depends on the duty cycle of the drive signal. We identify a regime in which the diffraction efficiency is linearly proportional to the duty cycle, thereby providing a linear drive characteristic.

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Em Interaction Of Handset Antennas And A Human In Personal Communications, Michael A. Jensen, Yahya Rahmat-Samii Jan 1995

Em Interaction Of Handset Antennas And A Human In Personal Communications, Michael A. Jensen, Yahya Rahmat-Samii

Faculty Publications

In personal communications, the electromagnetic interaction between handset-mounted antennas and the nearby biological tissue is a key consideration. This paper presents a thorough investigation of this antenna-tissue interaction using the finite-difference time-domain (FDTD) electromagnetic simulation approach with detailed models of real-life antennas on a transceiver handset. The monopole, side-mounted planar inverted F, top-mounted bent inverted F, and back-mounted planar inverted F antennas are selected as representative examples of external and internal configurations. Detailed models of the human head and hand are implemented to investigate the effects of the tissue location and physical model on the antenna performance. Experimental results are …

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Partial Pixels: A Three-Dimensional Diffractive Display Architecture, Gregory P. Nordin, M. W. Jones, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Parker Jan 1995

Partial Pixels: A Three-Dimensional Diffractive Display Architecture, Gregory P. Nordin, M. W. Jones, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Parker

Faculty Publications

We describe in detail the partial pixel architecture that permits the realization of three-dimensional (3-D) displays that are functionally equivalent to a real-time holographic stereogram. This architecture permits the simultaneous presentation of multiple stereoscopic images so that motion parallax is discernible in the resultant 3-D scene. The key innovation of the architecture is that each pixel is subdivided into partial pixels, which in turn can be implemented as individual diffraction gratings. We describe a static display that exhibits a 3-D image with one-dimensional motion parallax, thereby demonstrating key features of the architecture. A variety of partial pixel implementations are discussed …

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