The invention provides for a broad band directional antenna (10) comprising a ground plane (12) having an axis (14) extending perpendicularly to the ground plane, an active radiator (13) which is axially spaced from the ground plane, a metamaterial ground plane assembly (16) and a conductive pillar (28.1) between the first conductive wall and the ground plane. The metamaterial ground plane assembly comprises a metamaterial ground plane (17), a first conductive wall (20) adjacent a periphery of the metamaterial ground plane, the first conductive wall having a bottom (22) and atop (24) and a second wall (26) comprising two mutually insulated conductive wall parts (26.1, 26.2) located spaced from and outside of the first conductive wall. The bottom of the first conductive wall is located between the ground plane and the metamaterial ground plane and the top of the first conductive wall is located beyond the active radiator.