Design of tunable modes and dual-band circular patch antenna using shorting posts

A simple analysis tool is presented, which can predict the resonant frequencies of all normal modes of a circular patch radiator when loaded with a number of passive conducting posts, distributed along the circumference of a circle concentric with the patch radiator. Two specific cases are investigated, where either the resonant frequencies can be tuned in a predictable manner or a closely spaced dual-band antenna with flexible band separation can be designed. It is also shown that for a perturbed circular patch TM₀₁ is the mode with lowest non-zero resonant frequency