Self-Complementary Hyperbolic Metasurface Antennas

Abstract

Anisotropic Self-Complementary Metasurfaces (SCM) are structures constituted by a “self-dual” (according to Babinet’s duality principle) alternance of inductive and capacitive complementary strips. They support orthogonally polarized surface-wave modes with the same phase velocity in the principal direction of propagation. The isofrequency dispersion curves of these modes are hyperbolas, and therefore these metasurfaces (MTSs) fall in the category of hyperbolic MTSs. It is shown here that the hyperbolas may degenerate in same cases into almost straight lines, which implies that the velocity of energy transport is constantly directed along the complementary strips at any frequency and for any possible phasing orthogonal to the strips. In this circumstance, the SCM can be conveniently used to design dual-polarized leaky-wave antennas by modulating the impedances of the complementary strips. Each strip behaves as a channel, which can be independently fed with the desired phase and amplitude. We demonstrate here that these antennas exhibit a strong decoupling between both co-polar and cross-polar channels, even when the distance between strips is electrically small. This increases the performance of the antenna, especially in azimuthal beam scanning. A prototype at 2.6 GHz has been constructed and successfully measured confirming the theoretical conjectures.