Patch antennas on externally perforated high dielectric constant substrates

Smaller physical size and wider bandwidth are two antenna engineering goals of great interest in the wireless world. To this end, the concept of exter nal substrate perforation is applied to patch antennas in this paper. The g oal was to overcome the undesirable features of thick and high dielectric c onstant substrates for patch antennas without sacrificing any of the desire d features, namely, small element size and bandwidth. The idea is to use su bstrate perforation exterior to the patch to lower the effective dielectric constant of the substrate surrounding the patch. This change in the effect ive dielectric constant has been observed to help mitigate the unwanted int erference pattern of edge diffraction/scattering and leaky waves. The numer ical data presented in this paper were generated using the finite-differenc e time-domain (FDTD) technique. Using this numerical method, a patch antenn a was simulated on finite-sized ground planes of two different substrate th icknesses, with and without external substrate perforation. The computation s showed the directivity drop in the radiation pattern caused by substrate propagation was noticeably improved by introducing the substrate perforatio n external to the patch for the case of a patch antenna on a relatively thi ck substrate without any loss of bandwidth. Measurements of a few patch ant ennas fabricated on high dielectric constant substrates with and without su bstrate perforation are included for completness. Good correlation between the computed results and mesurements is observed.