A compact low-profile high-impedance surface for use as an antenna ground plane

A compact and low-profile high-impedance surface is proposed which offers a significantly smaller footprint without affecting the usable reflection phase bandwidth of the structure. The unit cell of the proposed surface is similar to the traditional `mushroom´ structure, but utilizes inter-digitated-capacitor and spiral-inductor lumped elements to reduce its size without sacrificing the in-phase reflection bandwidth. It is determined that the reflection-phase resonance and bandwidth is largely independent of the shunt inductive loading and depends primarily on the value of the series capacitive loading. Finally, an application of the structure as a high-impedance ground plane for a printed loop antenna is proposed.