In low-profile applications, the antenna is often positioned very closely to an electrically conducting surface, or ground plane. Such a ground-plane backing significantly degrades antenna performance when the electrical height is less than λ/115. Existing approaches, such as lossless electromagnetic bandgap (EBG) structures and artificial magnetic conductors (AMC), tend to operate over a small bandwidth. This paper discusses two alternative ultra-wideband (UWB) approaches that laminate the ground plane with 'special magneto-dielectric (or ferrite) layers. The first approach employs a ferrite layer with a high μr/εr ratio to produce an in-phase reflection, similar to that caused by a perfect magnetic conductor (PMC). The second approach adapts a lossy ferrite with similar values of relative permeability, μr, and relative permittivity, εr. Radiation enhancements achieved via these ground-plane treatments will be demonstrated by simulated and measured examples. Design guidelines based on a parametric study will also be discussed.
