An antenna system, comprising: a plurality of radiating elements configured to transmit and receive electromagnetic energy and for producing circularly polarized radiation, each of the radiating elements comprising a surface-wave waveguide, the surface-wave waveguide comprising: a base conductive ground plane comprising opposite side edges; a pair of conductive side walls (102; 104), one conductive side wall extending from each side edge of the base conductive ground plane; a substrate comprising a dielectric material disposed on the base conductive ground plane and between the conductive side walls; a first surface wave channel and second surface wave channel 90 degrees out of phase with each other, each defined by an impedance sheet disposed on the substrate and between the conductive side walls, the impedance sheet comprising a predetermined impedance characteristic for transmitting an electromagnetic wave and a plurality of impedance elements and a plurality of tunable elements, wherein a tunable element of the plurality of tunable elements comprises a material with an electrically variable permittivity, and wherein the plurality of impedance elements of the impedance sheet of the second surface wave channel are configured to radiate with a polarization angle offset of 90 degrees relative to the first surface wave channel and the plurality of tunable elements are tunable for scanning a main radiation lobe of a radiation pattern generated by the antenna system over a range of angles in a direction perpendicular to a plane of the antenna system; and a center conductor disposed within the substrate between the base conductive ground plane and the impedance sheet, the center conductor extending a length of the surface-wave waveguide; and wherein adjacent surface-wave waveguides share a common conductive side wall. a base conductive ground plane comprising opposite side edges; a pair of conductive side walls (102; 104), one conductive side wall extending from each side edge of the base conductive ground plane; a substrate comprising a dielectric material disposed on the base conductive ground plane and between the conductive side walls; a first surface wave channel and second surface wave channel 90 degrees out of phase with each other, each defined by an impedance sheet disposed on the substrate and between the conductive side walls, the impedance sheet comprising a predetermined impedance characteristic for transmitting an electromagnetic wave and a plurality of impedance elements and a plurality of tunable elements, wherein a tunable element of the plurality of tunable elements comprises a material with an electrically variable permittivity, and wherein the plurality of impedance elements of the impedance sheet of the second surface wave channel are configured to radiate with a polarization angle offset of 90 degrees relative to the first surface wave channel and the plurality of tunable elements are tunable for scanning a main radiation lobe of a radiation pattern generated by the antenna system over a range of angles in a direction perpendicular to a plane of the antenna system; and a center conductor disposed within the substrate between the base conductive ground plane and the impedance sheet, the center conductor extending a length of the surface-wave waveguide; and