Accuracy of homogenization models for finite high-impedance surfaces located in the proximity of a horizontal dipole

The accuracy of different homogenization models is analyzed in the case of a dipole antenna located very close to a finite high-impedance surface (HIS). In the different models, the periodic structure is replaced by a homogeneous boundary condition with different degrees of accuracy. It is shown that the expressions for the input impedance of HIS, that are used to compute the reflection phase diagram for normal incidence, do not provide the sufficient accuracy needed for this type of near-field problems. The accuracy of the homogenization model can be gradually improved by taking into account the spatially dispersive terms due to the grounded substrate and to the frequency-selective surface (FSS) grid. Further, it is shown that by accurately modeling the spatial dispersion in such HIS structures, one is able to reproduce correctly the presence of TE surface waves that play important role in the operation of a HIS-based antenna. Indeed, the bandwidth of the HIS-based antenna over which it presents a good return loss and broadside patterns can be extended by using the these surface waves propagating on the HIS favorably.