Wideband Directive Antennas with High-Impedance Surfaces
Résumé
This chapter demonstrates that it is possible to design wideband antennas with metamaterials. High Impedance Surfaces (HIS) are used to improve wideband antennas' performances. In particular, the Artificial Magnetic Conductor (AMC) behavior is utilized in order to achieve a reflector which can be located very close to antennas, thereby leading to low profiles. AMC being inherently narrow band, it is shown that this does not necessarily limit the impedance bandwidth of AMC-based antennas. However, some issues regarding the radiation pattern remains when a wide operating band is considered. So this chapter proposes two different approaches to overcome to some extend these limitations. A first approach led to an optimized antenna using an AMC with lumped elements. A second approach is to identify current areas circulating over the AMC's surface which are responsible of radiation pattern degradations. This technique led to a hybrid AMC which largely enhanced antenna's performances over a wide band.