An antenna comprising a first resonator element ( 260 ) for coupling to an antenna feed ( 264 ) ; a second resonator element ( 262 ) for coupling to ground; the first and second resonator elements arranged to allow field coupling between the first and second resonator elements such that at a first frequency the first and second resonator elements co-operate to allow operation of the first and second resonator elements in a first mode wherein the direction of current flow in one resonator element is different from the direction of current flow in the other resonator element and at a second frequency the first and second resonator elements co-operate to allow operation of the first and second resonator elements in a second mode wherein the direction of current flow in one resonator element is substantially the same as the direction of current flow in the other resonator element.
1. An antenna comprising a first resonator element for coupling to an antenna feed; a second resonator element for coupling to ground; the first and second resonator elements arranged to allow field coupling between the first and second resonator elements such that at a first frequency the first and second resonator elements co-operate to allow operation of the first and second resonator elements in a first mode wherein the direction of current flow in one resonator element is different from the direction of current flow in the other resonator element and at a second frequency the first and second resonator elements co-operate to allow operation of the first and second resonator elements in a second mode wherein the direction of current flow in one resonator element is substantially the same as the direction of current flow in the other resonator element.
2. An antenna according to claim 1 , wherein the first resonator element has a first electrical length and the second resonator element has a second electrical length.
3. An antenna according to claim 1 , wherein the first mode is an inverted F type mode.
4. An antenna according to claim 1 , wherein the second mode is coupled monopole mode.
5. An antenna according to claim 1 , wherein the first resonator element forms a monopole antenna.
6. An antenna according to claim 5 , wherein the first resonator element is arranged in a planar configuration.
7. An antenna according to claim 1 , wherein the second resonator element forms a monopole antenna.
8. An antenna according to claim 1 , wherein the first and second resonator elements are arranged in a planar configuration.
9. An antenna according to claim 8 , wherein the first and second resonator elements are transversely separated in the plane of the resonator elements.
10. An antenna according to claim 8 , wherein the first resonator element is separated from the second resonator element in a plane parallel to the second resonator element.
11. An antenna according to claim 1 , wherein a dielectric substrate is disposed between the first and second resonator elements.
12. A communication device having an antenna according to claim 1 .
13. A communication device according to claim 12 , wherein the antenna is mounted internally to the communication device.
14. A communication device according to claim 12 , wherein the antenna is mounted externally to the communication device.
15. An antenna according to claim 1 , wherein in the first mode the second resonator element operates as a ground plane to the first resonator element.