volume | PIER Journals

2006-05-28

Bandwidth, q Factor, and Resonance Models of Antennas

Mats Gustafsson,

Dr. Mats Gustafsson

Department of Electroscience

Lund Institute of Technology

Sweden

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Sven Nordebo

Dr. Sven Nordebo

School of Mathematics and System Engineering

Vaxjo University

Sweden

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Progress In Electromagnetics Research, Vol. 62, 1-20, 2006

doi:10.2528/PIER06033003

Abstract

In this paper, we introduce a first order accurate resonance model based on a second order Padé approximation of the reflection coefficient of a narrowband antenna. The resonance model is characterized by its Q factor, given by the frequency derivative of the reflection coefficient. The Bode-Fano matching theory is used to determine the bandwidth of the resonance model and it is shown that it also determines the bandwidth of the antenna for sufficiently narrow bandwidths. The bandwidth is expressed in the Q factor of the resonance model and the threshold limit on the reflection coefficient. Spherical vector modes are used to illustrate the results. Finally, we demonstrate the fundamental difficulty of finding a simple relation between the Q of the resonance model, and the classical Q defined as the quotient between the stored and radiated energies, even though there is usually a close resemblance between these entities for many real antennas.

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Mats Gustafsson, and Sven Nordebo, "Bandwidth, q Factor, and Resonance Models of Antennas," Progress In Electromagnetics Research, Vol. 62, 1-20, 2006.
doi:10.2528/PIER06033003

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