No abstract

Abstract-Wireless power transfer via magnetic resonant coupling is experimentally demonstrated in a system with a large source coil and either one or two small receivers. Resonance between source and load coils is achieved with lumped capacitors terminating the coils. A circuit model is developed to describe the system with a single receiver, and extended to describe the system with two receivers. With parameter values chosen to obtain good fits, the circuit models yield transfer frequency responses that are in good agreement with experimental measurements over a range of frequencies that span the resonance. Resonant frequency splitting is observed experimentally and described theoretically for the multiple receiver system. In the single receiver system at resonance, more than 50% of the power that is supplied by the actual source is delivered to the load. In a multiple receiver system, a means for tracking frequency shifts and continuously retuning the lumped capacitances that terminate each receiver coil so as to maximize efficiency is a key issue for future work.

Library of Congress Cataloging-in-Publication Data Stancil, Daniel D.Theory of magnetostatic waves / Daniel D. Stancil p.cm. Includes bibliographical references and index.

In Chapter 1, we discussed the angular momenta and magnetic moments of individual atoms and ions. When these atoms or ions are constituents of a solid, it is important to take into consideration the ways in which the angular momenta on different sites interact with one another. For simplicity, we will restrict our attention to the case when the angular momentum on each site is entirely due to spin.The elementary excitations of coupled spin systems in solids are called spin waves. In this chapter, we will introduce the quantum theory of these excitations at low temperatures. The two primary interaction mechanisms for spins are magnetic dipole-dipole coupling and a mechanism of quantum mechanical origin referred to as the exchange interaction. The dipolar interactions are of importance when the spin wavelength is very long compared to the spacing between spins, and the exchange interaction dominates when the spacing between spins becomes significant on the scale of a wavelength. In this chapter, we focus on exchange-dominated spin waves, while dipolar spin waves are the primary topic of subsequent chapters.We begin this chapter with a quantum mechanical treatment of a single electron in a uniform field and follow it with the derivations of Zeeman energy and Larmor precession. We then consider one of the simplest exchangecoupled spin systems, molecular hydrogen. Exchange plays a crucial role in the existence of ordered spin systems. The ground state of H 2 is a two-electron exchange-coupled system in an embryonic antiferromagnetic state. It serves to illustrate the origins of the exchange interaction and also provides a vehicle for our discussion on the Heisenberg spin Hamiltonian in ferromagnetic solids. Charged Particle in an Electromagnetic FieldWe obtained the time-independent Schrödinger equation (1.46) by quantizing the total energy of a particle moving in an electrostatic potential. Since we also want to understand the effects of a magnetic field, we now concern

No abstract

No abstract

Abstract

No abstract