Integral equation analysis of a low-profile receiving planar microstrip antenna with a cloaking superstrate

Eliminating the electromagnetic interaction of a device with its background is a topic which attracts considerable attention both from a theoretical as well as from an experimental point of view. In this work, we analyze an infinite two-dimensional planar microstrip antenna, excited by an incident plane wave, and propose its potential operation as a low-profile receiving antenna, by suitably adjusting the parameters of its cloaking superstrate. We impose a semi-analytic integral equation method to determine the scattering characteristics of the microstrip antenna. The method utilizes the explicit expressions of the Green's function of the strip-free microstrip and yields the surface strip's current as the solution of a suitable linear system. Subsequently, the antenna's far-field response is obtained. Numerical results are presented for the achieved low profile of the receiving antenna, by choosing suitably the cloaking superstrate parameters. It is demonstrated that for specific cloaking parameters the scattered field by the antenna is considerably reduced, while the received signal from the antenna is maintained at sensible levels. We point out that the material values achieving this reduction correspond to a superstrate filled with an epsilon-near-zero or a low-index metamaterial. Finally, the variations of the device reaction for various superstrates are depicted, concluding that for optimized superstrate's parameters, the reaction values are significantly reduced, while at distinct scattering angles even approach zero.