2006 Events

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Advances in the microchip industry and nanotechnology call for electromagnetic simulation of structures that are very complex, but are still a tiny fraction of a wavelength. The demand for electromagnetic simulation of antennas on cars, aircraft, and radar scattering, calls for electromagnetic simulation of structures that are many wavelengths long. This talk describes recent advances in solving Maxwell’s equations for complex structures which are a tiny fraction of a wavelength to ultra large structures involving hundreds of wavelength using integral equation methods derived from first principle electromagnetics. Modern electromagnetic simulations often require many degrees of freedom to describe the geometry. Hence, we will describe fast and efficient methods to solve large and dense matrix systems that follow from integral equations.
A comparison between various kinds of numerical methods will be discussed. Then a brief overview of the fast algorithm, the multilevel fast multipole algorithm will be given. Extension of such fast algorithm to layered media and to very low frequencies will be presented. In order to capture quasi-static physics (circuit physics) and wave physics, a numerical solver has to work reliably in the very low frequency regime as well as the wave regime and the quasi-optical regime. Ways to overcome numerical instabilities associated with integral equations as well as acceleration techniques will be discussed.
We will show large-scale simulation examples from scattering, subsurface probing, antennas mounted on cars, and complex structures as encountered in computer circuits and chips.

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The decade of the nineties is highlighted with truly remarkable progress on our ability to carry out simulations, not only for large scale problems, but also in terms of hybridization and integration of passive and active RF circuits for a variety of applications. These developments have allowed for broadband antenna design, simulations of large multilayered and multifunctional antennas with embedded frequency selective surfaces (FSS), metamaterial substrate designs, MEMS analysis and design, large finite arrays and full scale aircraft scattering analysis using first principle methods, Electromagnetic coupling and interference of systems involving passive and active components, magnetic resonance imaging (MRI) simulations , indoor propagation and evaluation of wireless systems, etc. What is probably so remarkable is that a decade ago (early 90s), we had just started looking at three-dimensional applications and the development of practical simulation tools was seemingly far away. Today, we have access to robust and fast three dimensional algorithms for composite materials and have also demonstrated that simulations of practical vehicles or large finite antenna arrays, and possibly RF integrated systems can be carried out on a desktop PC. In addition, we have delved into topology optimization/design. The latter holds promise for novel antenna and microwave circuit design, RF filters and RFICs for mixed signal applications, and others.This presentation will provide an overview of frequency domain developments, with particular focus on hybrid formulations and fast methods and their integration with formal design methodologies for antenna applications.

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Retrodirective arrays are unique phased array systems that are capable of providing power gain in the direction of a received source with no prior knowledge of the source's location. When compared to fully adaptive arrays that adapt their beam patterns to the signal environment based on the received spatial signature, retrodirective arrays do not require the computational burden for antenna pattern adaptation. Traditionally, retrodirective arrays have been designed around analog methods such as doubled local oscillator phase conjugation and heterodyning for use in line of sight non-fading channels. This thesis describes a novel implementation of a retrodirective array for duplex digital communications and explains how retrodirective arrays can be used in flat fading channels to increase system performance. Measurements of the antenna pattern for a two element retrodirective array using flexible uplink and downlink modulation schemes are presented and show that the designed system is capable of tracking a signal source accurately under duplex communications conditions.

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Ferromagnets are important in numerous areas of electronics, including antennas and microwave devices, but their characteristic hysteretic behaviour is widely misunderstood. It has led to an extraordinary variety of different empirical models, most of which are only tenuously related to the underlying physics. In contrast, this talk introduces a simple theory that is based solely on quantum mechanics and classical physics. It provides a quantitative analytical description of numerous aspects of ferromagnetic phenomena. The theory introduces the concept of the domain-size function, which provides close links between the magnetization process at the quantum-dynamical scale, the behavior of the domains at the mesoscopic scale, and the measured characteristics of macroscopic samples. The theory is valid for materials ranging from extremely soft magnets to the hardest permanent magnets, with coercivities ranging over 6 orders of magnitude, and accounts for the relationships between the spatially-averaged domain size, the observed shapes of hysteresis loops, and the nature of the initial magnetization curve. Recent work indicates that the theory can also account for complex minor-loop behaviour, including first-order and second-order return curves (FORCs and SORCs). Examples of correlations between theory and measured data will be included.

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This talk describes the various university–industry linkage programs existing in the Indian higher education system, in the context of the technological revolution that’s sweeping the country.

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There are many popular numerical techniques for electromagnetic wave modeling. These techniques can be divided into the frequency-domain and time-domain methods.