Investigation of radiation gain enhancement techniques for microstrip patch antenna in multilayer superstrate

An analytical methodology is described that gives insight into the behaviour of a microstrip patch antenna covered by multiple planar dielectric and magnetic superstrates. The expressions for the electric field in TM01 mode are combined with a multilayer media transmission line model to investigate the effect on the radiation pattern and gain. Design parameters such as relative permittivity or permeability value, thickness of the superstrate layer, and layer separation are optimised to maximise the antenna gain. Conditions for significant improvements in boresight gain were identified from the model and demonstrated by radiation pattern measurements on some multilayered prototype antennas.