A circularly polarized antenna configured to receive radiation at global navigation satellite system, GNSS, frequencies, comprising: a dielectric substrate; a circular patch overlying the dielectric substrate; one or more impedance transformers, each of the one or more impedance transformers including a microstrip overlying the dielectric substrate and a ground pad separated from the microstrip by a dielectric, each microstrip coupled to an antenna feed at an input and coupled to the circular patch at an output, and each ground pad coupled to ground;and a metamaterial ground plane comprising: a plurality of conductive patches (110c1; 110c2; 110c3) arranged along a first plane below the circular patch and separated from the circular patch by at least the dielectric substrate, each conductive patch separated from others of the conductive patches, and the plurality of conductive patches arranged in a pattern that provides circular symmetry with respect to a center of the circularly polarized antenna; a ground plane arranged along a second plane, the ground plane electrically coupled to at least a first portion of the plurality of conductive patches; and a conductive fence (146, 148, 150, 152) extending around a perimeter of the plurality of conductive patches and around a perimeter of the ground plane, wherein the ground plane and the conductive fence are coupled to ground; wherein the circularly polarized antenna further comprises a discontinuous ring comprising discrete conductive elements surrounding the circular patch, each of the discrete conductive elements coupled to ground and isolated from the circular patch. a dielectric substrate; a circular patch overlying the dielectric substrate; one or more impedance transformers, each of the one or more impedance transformers including a microstrip overlying the dielectric substrate and a ground pad separated from the microstrip by a dielectric, each microstrip coupled to an antenna feed at an input and coupled to the circular patch at an output, and each ground pad coupled to ground;and a metamaterial ground plane comprising: a plurality of conductive patches (110c1; 110c2; 110c3) arranged along a first plane below the circular patch and separated from the circular patch by at least the dielectric substrate, each conductive patch separated from others of the conductive patches, and the plurality of conductive patches arranged in a pattern that provides circular symmetry with respect to a center of the circularly polarized antenna; a ground plane arranged along a second plane, the ground plane electrically coupled to at least a first portion of the plurality of conductive patches; and a conductive fence (146, 148, 150, 152) extending around a perimeter of the plurality of conductive patches and around a perimeter of the ground plane, wherein the ground plane and the conductive fence are coupled to ground; a plurality of conductive patches (110c1; 110c2; 110c3) arranged along a first plane below the circular patch and separated from the circular patch by at least the dielectric substrate, each conductive patch separated from others of the conductive patches, and the plurality of conductive patches arranged in a pattern that provides circular symmetry with respect to a center of the circularly polarized antenna; a ground plane arranged along a second plane, the ground plane electrically coupled to at least a first portion of the plurality of conductive patches; and a conductive fence (146, 148, 150, 152) extending around a perimeter of the plurality of conductive patches and around a perimeter of the ground plane, wherein the ground plane and the conductive fence are coupled to ground; wherein the circularly polarized antenna further comprises a discontinuous ring comprising discrete conductive elements surrounding the circular patch, each of the discrete conductive elements coupled to ground and isolated from the circular patch.