Abstract: The object of the present invention is to achieve an antenna for both receiving and transmitting circularly polarized RF signals which is smaller and lighter than prior art antennas as well as to achieve one antenna for both receiving and transmitting circularly polarized RF signals which has better characteristics for a given physical length than prior art antennas. This is achieved by providing an N-helical-filar antenna with N radiating elements coaxially arranged and defining a cylindrical envelope where each individual radiating element is capacitively coupled to another radiating element.

Abstract: An antenna system including an antenna device and feed device for transmitting and receiving circularly polarized RF waves in a first mode of operation, and of linearly polarized RF waves in a second mode of operation, and a hand-held mobile communication device provided with such an antenna system. A radiating structure (10) including N helical radiating elements (12A-D), being coextending and coaxially arranged on a support structure (11) are fed in order to provide for transmission/reception of circularly polarized RF waves in the first mode of operation. N is an integer greater than one. Further, means (24A-D, 16, 17, 19, 25, 25A) are arranged for essentially uniform excitation of the helical radiating elements (12A-D) in order to provide for transmission/reception of linearly polarized RF waves in the second mode of operation.