Radiation efficiency enhancement of a horizontal dipole on an electrically thick substrate by a PMC ground plane

A method for the enhancement of the radiation efficiency of horizontal electric radiators on grounded substrate at low-efficiency substrate thicknesses, corresponding to TM surface-wave cutoff frequencies, is presented. This method consists in placing a thin (high permittivity) dielectric slab between the initial slab and the ground plane so as to generate an equivalent perfect magnetic conductor (PMC) condition at the bottom of the main substrate. Full-wave simulation results have demonstrated an efficiency enhancement to 40% from a non-radiating dipole at the cutoff frequency of the second TM surface-wave mode. This method can be used to provide more design flexibility in high-efficiency planar antennas in the millimeter-wave regime, where the substrates are typically electrically very thick.