Surface Wave Suppression for Improved Isolation and Bore-Sight Gain Based on Dipole Moment Conversion

Abstract

This article proposes a novel approach to surface wave suppression based on dipole moment conversion for isolation and bore-sight gain improvement. To transform the power associated with the surface wave into the source of the radiating wave, an inverted-L shape composed of a thin strip with a via post is adopted. Unlike the conventional mushroom structure, the via post is placed at the leading edge of the strip, so that the longitudinal edge of the strip is aligned with the propagation direction of the surface wave. This inverted-L structure plays a key role in converting the vertical electric dipole moment to the horizontal component, and the conversion efficiency can be further improved by arranging the structure with a narrower interval of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.057\lambda $ </tex-math></inline-formula> in the axis perpendicular to the propagation direction. For validation, multipole moments are calculated from induced currents, and the proposed metasurface is fabricated for two array configurations. Scattering parameters and near- and far-fields are measured to demonstrate the proposed approach experimentally. The fabricated metasurface shows an operating frequency band from 9.74 to 10.62 GHz, and its average isolation and bore-sight gain are improved by 6.3 and 1.6 dB, respectively, without any severe distortion on impedance matching.