3
Wideband Directive Antennas with High Impedance Surfaces
3.1 Introduction
In recent years, there has been a growing interest in applying artificial materials, known as metamaterials, to antennas. This generic term covers a variety of definitions: left-handed material (LHM), high impedance surface (HIS), epsilon-near-zero (ENZ), and mu-near-zero (MNZ). A common thread to all these definitions is that these materials derive their unique properties not from their composition but from their structure. They are mostly composed of a periodic arrangement of materials, patterns. This spatial periodicity naturally induces a spectral selectivity. This narrow bandwidth is, in addition to losses, one of the main limitations for metamaterials applications.
The objective of this chapter is to demonstrate that it is possible to design wideband antennas with metamaterials. Among the above-mentioned variety of metamaterials, it focuses on high impedance surfaces (HISs), introduced by Sievenpiper in Reference [1]. These surfaces can be used in order to improve antennas by reducing their thickness and making them unidirectional rather than bidirectional. Thus, designing unidirectional antennas is required on many platforms (aircrafts, unmanned aerial vehicles, etc.) in order to obtain outward radiation and preserve the interior of any electromagnetic pollution. Furthermore, for integration ...
