31 research outputs found
Broadband isotropic ÎĽ-near-zero metamaterials
Natural diamagnetism, while being a common phenomenon, is limited to permeability values close to unity. Artificial diamagnetics, to the contrary, can be engineered to provide much lower values and may even possess an effective permeability close to zero. In this letter, we provide an experimental confirmation of the possibility to obtain extremely low permeability values by manufacturing an isotropic metamaterial composed of conducting cubes. We show that the practical assembly is quite sensitive to fabrication tolerances and demonstrate that permeability of about μ = 0.15 is realisable. © 2013 AIP Publishing LLC
TE Surface Wave Resonances on High-Impedance Surface Based Antennas: Analysis and Modeling
Low-profile antennas comprising a horizontal dipole
above a high-impedance surface are analyzed. The emphasis of
this paper is on the additional resonances of the radiating structure
caused by surface waves propagating on the high-impedance
surface. It is shown that such resonances can be favorably used
for broadening the bandwidth of the antenna. The phenomenon
is thoroughly modeled by exploiting a parallel between the HIS
structure and a waveguide resonator. In the second part of the
paper we discuss homogenized approaches for modeling the radiating
properties of the antenna with emphasis to the phenomenon
discussed in the first part. As it turns out, it is necessary to take
into account the spatially dispersive properties of high-impedance
surfaces, and most of the simplified models commonly used for analyzing
high-impedance surface based antennas fail in predicting
the discussed resonance mode
An antenna model for the Purcell effect
The Purcell effect is defined as a modification of the spontaneous emission rate of a quantum emitter at the presence of a resonant cavity. However, a change of the emission rate of an emitter caused by an environment has a classical counterpart. Any small antenna tuned to a resonance can be described as an oscillator with radiative losses, and the effect of the environment on its radiation can be modeled and measured in terms of the antenna radiation resistance, similar to a quantum emitter. We exploit this analogue behavior to develop a general approach for calculating the Purcell factors of different systems and various frequency ranges including both electric and magnetic Purcell factors. Our approach is illustrated by a general equivalent scheme, and it allows resenting the Purcell factor through the continuous radiation of a small antenna at the presence of an electromagnetic environment