Antenna

An antenna comprising a feedline 101 with perpendicular arms 1011, 1012 and a radiator 103 separated by a ground plane 102 which contains a slot 1021 and is spaced from and parallel to the feedline 101 and the radiator 103, where when the feedline 101 is projected onto the ground plane 102 the slot intersects with the perpendicular feedline arms 1011, 1012. The feedline 101 is electromagnetically coupled to the slot 1021 and may be formed from a microstrip or stripline. The slit 1021 may be arcuate, elliptical or circular and have a bisector equal to the bisector of the feedline arms 1011, 1012. There may be additional slots in the ground plane for dual frequencies, such as Wi-Fi and GSM, and additional slots in the radiator 103. The radiator 103 may be divided into inner and outer circular sections and printed or plated onto a case housing the antenna. The ground plane slot 1021 length may provide a 90 degrees phase shift between feed arms 1011, 1012 to produce circular polarisation.