Main menu >> Electrical and Computer Engineering >> Electromagnetics

Electrical and Computer Engineering

Electromagnetics
^ Intelligent Portable Antenna Systems for High-Speed Wireless Communication
J. T. Bernhard*
National Science Foundation CAREER Award, ECS 99-83460

High-speed wireless data communication faces two challenges: high error rates caused by interference and unpredictable environments, and limited functionality and battery life at the portable unit. "Intelligent" or "smart" antenna systems that respond to changing operating conditions can help meet these challenges. This research develops intelligent portable antenna systems to improve the reliability, throughput, and noise immunity of high-speed wireless communication networks. Specifically, this project implements new compact radiation-tunable antennas with a performance-driven fuzzy controller. This novel approach views portable antennas as dynamic components of the communication system, creating a new paradigm for antenna design and control.

^ Internal Antenna Systems for Portable Wireless Communications
J. T. Bernhard*
Amphenol T&M Antennas

As wireless communication moves to higher and higher data rates, portable wireless devices will come in many different shapes and sizes to deliver a range of wireless services. This research develops guidelines for the design of internal antenna systems that improve connection reliability and battery life of portable devices while reducing the consumer exposure to radiated electromagnetic fields. The work includes consideration of pertinent chassis materials and possible antenna integration positions.

^ Microstrip Antennas with Broadband Integrated Phase Shifting
J. T. Bernhard*
National Aeronautics and Space Administration, NCC3-780

Typically, cost and weight limit phased array antenna technology. Two main sources of expense lie in the MMIC phase shifters and amplification networks required to counteract the signal losses incurred in these phase shifters. This research develops a microstrip antenna that incorporates a thin ferroelectric layer. An applied DC voltage bias to the antenna will change the ferroelectric layer's electrical properties, resulting in an apparent phase shift of the signal transmitted or received by the antenna. This structure will eliminate the need for a separate phase shifter and has the potential to create more economical and more compact phased arrays.

^ Novel Active Antenna Elements for High-Performance Phased Reflectarrays
J. T. Bernhard*
University of Illinois

The objective of this research is a new active antenna element for reflectarrays in military, space, and commercial applications. This new element will incorporate signal reception, amplification, and transmission functions in a single fabrication layer by including an MMIC amplifier inside the footprint of a microstrip antenna. Compared to current designs, arrays composed of these elements will exhibit increased radiated power efficiency and higher polarization purity while possessing smaller size, weight, and fabrication complexity.

^ Center for Computational Electromagnetics of Complex Structures
W. C. Chew,* J. M. Jin, E. Michielssen, J. M. Song
U.S. Air Force Office of Scientific Research, AFOSR F49620-96-1-0025

This multimillion-dollar project encompasses five key goals: substantially advance knowledge in developing fast algorithms for solving integral equations of electromagnetic scattering with reduced computational complexity and memory requirements; enhanced ability to solve partial differential equations of magnetic scattering by reducing grid-dispersion error and modeling error; hybridization with high-frequency methods to further expand the class of problems that can be handled in addition to fast numerical methods; parallelization of algorithms on massively parallel machines and distributed systems to harness maximal throughput from present day computers; and development of computational engines as workhorses and application-specific modules for easy interfacing with real-world applications problems.

^ Enhancements to and Characterization of the Very Early Time Electromagnetics (VETEM) Prototype Instrument and Applications to Shallow Subsurface Imaging of Sites in the DOE Complex
W. C. Chew,* T. J. Cui, A. Aydiner
U.S. Department of Energy, DE-FG07-97ER14835

This project is in collaboration with the U.S. Geological Survey (USGS) to study the very early time electromagnetic (VETEM) system for the detection, imaging, and characterization of landfills. A combination of hardware and software enhancement to the present system will be studied. The role of University of Illinois researchers will be mainly concentrated on software enhancement using novel computational electromagnetics methods and inverse scattering methods. Hence, this study will include physical modeling, numerical forward and inverse modeling, and antenna modeling over layered and subsurface media. The software modeling and inverse modeling capabilities will in turn help USGS with the hardware design and enhancement of the VETEM system as a better waste and landfill characterization tool.

^ Nonlinear Inverse Scattering Method for 3-D Objects
W. C. Chew,* T. Cui, A. Aydiner
National Science Foundation, ECS 99-06651

In this project, researchers study an efficient nonlinear inverse scattering method for 3-D objects. Inverse scattering involving 3-D objects is a difficult subject because of the computational workload and the ill-posedness of the problem. This project studies the use of fast solvers to solve the forward scattering problem, which in turn drives the inverse scattering algorithm via a distorted Born iterative method. The distorted Born iterative method is a gradient search approach where the gradient is found by solving the forward scattering problem. Researchers propose to use the multilevel fast multipole algorithm and FFT-based algorithms for the forward scattering part.

^ Advanced Integral Equation Computer Program
J. Jin,* M. Kowalski, B. Singh
Mission Research Corp.

The objective of this project is to develop advanced physics-based basis functions for the integral equation solution of electromagnetic scattering problems. Such basis functions would increase the maximum electrical dimension of structures analyzed using method-of-moments-based computer programs. The simulation capability will be further enhanced by utilizing a multilevel fast multipole iterative solver.

^ Characterization of Interaction of Electromagnetic Fields with Biological Objects
J. Jin,* W. C. Chew
National Science Foundation, ECS 94-57735

The interaction of electromagnetic fields with biological objects such as a human body is an important issue in MRI and microwave hyperthermia applications. Better understanding of such interactions can not only provide vital safety information, but can also enable engineers to design better and new devices. In this project, researchers develop highly accurate and efficient three-dimensional computational methods for simulation of the interaction of electromagnetic fields with biological objects.

^ Fast Frequency-Sweep Analysis of Electromagnetic Problems
J. Jin,* D. Jiao, F. Ling
U.S. Air Force Office of Scientific Research, MURI Program

This project applies the asymptotic waveform evaluation method to a variety of electromagnetic problems for a fast frequency-sweep analysis. These problems include scattering by a perfectly electric conducting (PEC) body, radiation of wire antennas on a PEC body, scattering by a dispersive dielectric body, scattering and radiation of conformal cavity-backed microstrip patch antennas, and microstrip circuits in a multiplayer medium. The use of AWE can speed up the analysis by more than an order of magnitude.

^ High-Order Computational Electromagnetics Technology
J. Jin,* K. Donepudi, J. Liu, J. Song, W. C. Chew
U.S. Air Force Office of Scientific Research, MURI Program

The objective of this project is to develop high-order computational electromagnetics methods for a variety of electromagnetic problems such as antennas, scattering, and circuit. The high-order methods include the differential-equation based ones (such as the finite-element method) and the integral-equation based ones (such as the method of moments and fast multipole method). These methods can provide a much more accurate modeling of problem geometry as well as more accurate representation of electromagnetic fields and electric currents.

^ Hybrid Methods for Electromagnetic Scattering
J. Jin*
U.S. Air Force Office of Scientific Research, MURI program

In this project, researchers develop hybrid numerical methods to compute electromagnetic scattering from realistic three-dimensional targets. These hybrid methods combine high-frequency techniques (such as the shooting-and-bouncing-ray technique) and low-frequency technique (such as the finite-element and integral equation methods) to take the advantages and eliminate the disadvantages of both. As a result, they are accurate and efficient and can be applied to large, complex targets.

^ Three-dimensional Finite-Element Method for Electromagnetic Field Computation
J. Jin*
National Science Foundation, ECS 94-57735

The goal of this project is to develop a finite-element method using vector elements for electromagnetic analysis of electronic devices, circuits, antennas, and radar scattering. Special emphasis is on the method's accuracy, efficiency, and versatility. Both frequency and time-domain methods will be investigated and evaluated. Specific applications will be demonstrated.


Summary of Engineering Research