Bandwidth Enhancement of the Resonant Cavity Antenna by Using Two Dielectric Superstrates

We propose a novel approach to enhance the bandwidth of the high directivity of the resonant cavity antenna (RCA) by applying two dielectric layers as superstrates. The approach is based on creating two cavities corresponding to two operating frequency bands that combine to form a single wide band of operation. The RCA design is discussed in a methodological manner to determine the thicknesses of the superstrates, the separation distance between them, and the separation distance to the ground plane. We show that the proposed technique is capable of enhancing the bandwidth from 9% of the single superstrate RCA to 17.9% of the two superstrate RCA, with only 0.1-dB reduction of the maximum directivity (17.5 dBi). The presented design method can be replicated for any RCA with any directivity level and type of primary feeding. The performance of the analytically designed antenna is validated by simulation using commercial numerical electromagnetics software.