Radiation characteristics of microstrip dipole antennas over a high-impedance metamaterial surface made of Hilbert inclusions

We analyze numerically the radiation characteristics of center-fed microstrip short dipoles and half-wave dipoles near a high-impedance surface made of Hilbert shape flat inclusions. We study the input impedance, pattern and gain of such radiating structures. We show that the radiation resistance of a microstrip dipole increases noticeably at certain frequencies near the resonant frequency of the Hilbert surface. Moreover, antenna gain enhancement at certain frequencies is observed for all dipole sizes we have analyzed.