APPLICATIONS OF
METAMATERIALS TO REALIZE
EFFICIENT
ELECTRICALLY SMALL ANTENNAS
Richard W. Ziolkowski
Kenneth
von Behren Chaired Professor
Department
of Electrical and Computer Engineering
The
1230
Tucson, AZ 85721-0104 USA
Tel: (520) 621-6173, Fax: (520) 621-8076
E-mail: ziolkowski@ece.arizona.edu
Metamaterials
are engineered media whose electromagnetic responses are different from those
of their constituent components. They are often generated by incorporating in a
periodic manner various types of artificially fabricated, extrinsic, low
dimensional inhomogeneities in some background
substrate. Metamaterials that mimic known material
responses or that qualitatively have new response functions that do not occur
in nature have been realized.
One class of metamaterials that has already demonstrated its usefulness
with small antennas is the artificial magnetic conductor (AMC). The AMC designs
include, for example, the Sievenpiper class of
mushroom surfaces, the UCLA class of UC-PBG surfaces, and the Arizona capacitively loaded loop (CLL) volumetric metamaterial [A. Erentok, P. Luljak, and R. W. Ziolkowski, to
appear in IEEE Trans. Antennas Propagat Special Issue
on AMCs]. This general class of metamaterials
will be reviewed with particular emphasis on the design, fabrication and
measurement of the
The effect of surrounding an
electrically small dipole antenna with a shell of double negative (DNG)
material (
< 0 and 
< 0) has been investigated both analytically and
numerically [R. W. Ziolkowski and A. D. Kipple, IEEE Trans. Antennas Propagat.,
vol. 51, pp. 2626-2640, October 2003]. Analysis of the reactive power within
this dipole-DNG shell system indicates that the DNG shell acts as a natural
matching network for the dipole and free space. Resonances occur at particular
shell sizes and results in significant enhancements of the radiated power with
corresponding decreases in the radiation Q. These results have been extended
recently to lossy DNG and to epsilon negative (ENG) metamaterials. Similar performance enhancements have been
predicted. We have also demonstrated reciprocity between these source results
and the scattering of plane waves from the corresponding metamaterial
coated spheres in agreement with the enhanced scattering predictions given by
A. Alu and N. Engheta, for
instance, in [A. Alu and N. Engheta,
Proceedings of the ICEAA’03 Meeting, Session 14,