Dielectric-loaded antenna

A dielectric-loaded loop antenna for operation at frequencies above 200 MHz comprising an elongate dielectric core formed of a solid material having a relative dielectric constant greater than 5 and, on or adjacent the surface of the core, a three-dimensional antenna element structure including at least a pair of laterally opposed elongate antenna elements which extend between longitudinally spaced-apart positions on the core, and at least one linking conductor extending around the core to interconnect the said elements of the pair, the elongate elements having respective first ends coupled to a feed connection and second ends coupled to at least one said linking conductor, wherein the said elongate elements and the linking conductor or conductors together form at least two looped conductive paths each extending from the feed connection to a location spaced lengthwise of the core from the feed connection, then around the core, and back to the feed connection, the electrical length of one of the two paths being greater than that of the other path and extending around the core on the opposite side thereof from the other path, wherein said linking conductor comprises a conductive sleeve encircling the core, the elongate elements of said pair being connected at their respective second ends to a rim of the sleeve to provide first and second conductive linking paths between the elongate elements around respective opposite sides of the core, and wherein the rim is stepped such that the first linking path extends around one side of the core substantially at a first longitudinal location and the second linking path extends around the other side of the core substantially at a different, second longitudinal location.

A handheld radio communication unit, the handheld radio communication unit comprising:

• a radio transceiver,
• an integral earphone for directing sound energy from an inner face of the unit which, in use, is placed against an ear of a user;
• and
• an antenna comprising:
• a dielectric core having a central axis and formed of a solid material having a relative dielectric constant greater than 5 and, on or adjacent the surface of the core, a three-dimensional antenna element structure including first and second elongate parts which are laterally opposed with respect to each other and which each comprise at least two mutually adjacent and generally parallel elongate conductors extending between axially spaced-apart positions on the core, and linking conductors extending around the core to interconnect said elongate parts, said elongate parts having respective first ends coupled to a feed connection and second ends coupled to the linking conductors, wherein said first and second elongate parts and said linking conductors together form at least two looped conductive paths each extending from the feed connection to a location spaced lengthwise of the core from the feed connection, then around the core, and back to the feed connection, the electrical length of one of the two paths being greater than that of the other path at an operating frequency of the antenna, and wherein the first and second ends of the elongate antenna element structure parts lie generally in a common plane and the antenna is mounted in the unit such that the common plane lies generally parallel to the inner face of the unit so that a null in the radiation pattern exists in the direction of the user's head.