Chapter 9Wideband Antennas and ArtificialMagnetic Conductors1




9.1. Introduction

Metamaterials have recently been applied to antennas even though in the past they have already been used under other names (e.g. corrugated horns). This generic term covers a variety of definitions: left-handed material (LHM), electromagnetic band gap (EBG) material, artificial magnetic conductor (AMC), high impedance surface (HIS), etc. 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. This spatial periodicity naturally induces a spectral selectivity and then you can legitimately ask the question: can I expect some improvements to my wideband antenna system using these metamaterials?

The aim of this chapter is to provide some answers. At first, we will specify the nature of the metamaterial we will use, in this case AMC, without and with losses.

The initial objective of this work is the thickness reduction of unidirectional planar antennas. Usually unidirectionality is achieved using a cavity filled with thick absorbent. The idea is to replace the bulky absorbent with a thin absorbent or a particular reflector closest to the antenna and wideband. After having characterized them, we will associate some AMC with antennas which have bandwidths ranging from several percent to several tens of percent to demonstrate the improved performance ...

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