Bandwidth enhancement of the cavity resonance antenna (CRA) using multiple dielectric superstrate layers

The ray-tracing method is applied to study the radiation of a cavity resonance antenna (CRA) with both single and multiple dielectric superstrate layers. The behavior of the broadside directivity is investigated by analyzing the reflection phase of the antenna superstrates. To enhance the bandwidth of the CRA and maintain its large broadside directivity, a multilayered superstrate of an increasing reflection phase with frequency is presented. When compared to the single-layered CRA, a bandwidth enhancement of more than 100% is attained using a multilayered CRA of three superstrate slabs. Theoretical results are validated by simulations using commercial numerical electromagnetics software.