Summary
International Symposium on Antennas and Propagation
2008
Session Number:2B03
Session:
Number:2B03-3
Anomalous Power Radiation from Material and Metamaterial Resonances
Lotfollah Shafai, Malcolm Ng Mou Kehn,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
A number of recent papers have investigated the radiation field of antennas embedded in metamaterials and/or radiation from resonating modes inside material/metamaterial discontinuity layers [1]. It has been shown that the radiated power can be enhanced significantly at such resonances, which is a source of curiosity for electromagnetic community. In this paper we have investigated the problem using a practical antenna geometry that can be fed easily using common microwave waveguides, coaxial cables through baluns, or other transmission lines as practical antenna feeds. As such, the antenna input must be impedance matched to the feeding transmission line, and the radiated power must be accounted for through the source input power together with the resistive losses of the antennas and those inside the materials enclosing them. In other words, the causality condition must be satisfied and the energy conservation law must prevail, meaning, the radiated power must be equal to the difference of the source power and the resulting power losses in the entire structure. It is shown that the enhanced radiated power is not a physical reality, but it is a consequence of the way the problem is solved mathematically, which fails at resonances, and in the close proximity of the mode resonances. Thus, the solutions give unrealistic radiated power results, in effect violation the conservation of energy law.