Printed annular metasurface for omnidirectional dual-pol leaky-wave antennas

A printed annular metasurface (PAM) consisting of suitably designed concentric ring slots etched in a metal screen is proposed to realize two-dimensional leaky-wave antennas (LWAs) operating on a pair of azimuthally independent TM and TE cylindrical leaky modes. The metasurface, used as a superstrate for a grounded dielectric slab, is designed to obtain the desired wavenumbers for the two leaky modes. These are excited independently by means of a vertical coaxial probe and a horizontal microstrip loop, thus allowing for radiation of an omnidirectional conical beam with given beam angle and polarization. Theoretical and numerical investigations are presented, including an ad-hoc moment-method approach for the calculation of the antenna far-field patterns.