There is disclosed an antenna device relating to a single or dual band antenna system for use in mobile telecommunications devices, laptop and tablet computers, USB adapters and electrically small radio platforms comprising a pair of antennas attached to a conductive ground plane, the antennas being separated by free space in which at least one notch is formed in the conductive ground plane between the pair of antennas characterized in that the notch further includes an inductive component and a capacitive component providing good antenna isolation so as to enable MIMO operation or diversity operation.