All-dielectric compact superstrates for high-gain resonant-cavity antennas: designs and measurements

This paper presents the designs and measurements of two compact single-layer all-dielectric resonant-cavity antennas (RCAs). Both the antennas are compact (footprint < 5.5λ²₀) and low in profile (overall height < 0.9λ₀). The first RCA consists of a single-layer partially reflecting superstrate (PRS) in which thickness and permittivity vary from the center towards the edge of the PRS. Four commercially available dielectric materials are used to achieve this permittivity variation. This RCA demonstrates a measured peak directivity of 20.7 dBi and its 3dB directivity bandwidth extends from 12.75-19 GHz, which is 57% at the center frequency. The second RCA, made out of a single dielectric material demonstrates a measured peak directivity of 20.3 dBi and its measured 3dB directivity bandwidth is 55.9%. This class of compact single-layer RCAs, with a directivity bandwidth product per unit area (DBP/A) of greater than 1200, successfully overcomes the trade-off between directivity, bandwidth, profile and footprint and breaks the challenging barrier that has existed for RCAs over the last decade (and other planar high-gain antennas).