List of research proposal

Abstract

Triggered by the release in Feb., 2002 by the Federal Communications Commission of their first authorization for UWB[1], UWB research has been making fast progress across the world. The applications of UWB technology range from multimedia communications, through radar and biomedical image reconstruction, to positioning. Most of the system development for these applications requires the numerical simulation of UWB propagation because field campaigns tend to be expensive. UltraWideBand (UWB) system development requires numerical simulations which reproduce the behaviour of physical electromagnetic waves; equipment with which to study UWB devices physically is expensive and a field optimization and evaluation of the setup is usually performed using numerical simulations. An example of a UWB system is three dimensional (3D) short range biomedical imaging to view unobtrusively inside the body without the high cost of magnetic resonance imaging. The analysis of electromagnetic propagation is based on Maxwell's equations. The finite difference time domain (FDTD) method is one of the most widely used differential time domain numerical modeling methods as it is robust, fast and simple to implement and allows simulation of responses in a chosen frequency band from a single simulation. Maxwell's (differential form) equations are approximated to central-difference equations, and discritized. This approximation introduces numerical noise which would not appear in the real world. Many studies have attempted the 100 percent suppression of this numerical noise against the wave propagation theory in vain. All the research topics below are related to either accuracy, stability, reduction of the computational resources , such as computational time and memory, required for the numerical simulation of UWB spherical wave propagation. FDTD is capable of explicitly computing macroscopic transient electromagnetic interactions with general 3D geometries. However, FDTD formulations were not capable of analyzing the wave propagation in lossy radio environment because the permittivity and conductivity were specified as frequency independent constants, whilst these parameters vary with frequency in lossy media for UWB systems. To overcome this problem, a variety of FD-FDTD methods [2] have been proposed. The inclusion of frequency dependency was realized with the cost of calculation time. To reduce the computational cost of FD-FDTD by removing the Courant-Friedrichs-Lewy (CFL) stability condition [3], the ADI scheme [4] was introduced to FD-FDTD[5] (called FD-ADI-FDTD). This time, the computational efficiency was realized with the reduction of accuracy. By nature, all the finite differencing schemes experience numerical dispersion even when the radio environment is free space. [6], [7] have …

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