Retractable dual-band tapped helical radiotelephone antennas

Abstract

Radiotelephones having retractable antenna systems are disclosed which include a helix antenna coupled to an extendible rod antenna. When the rod antenna is in the retracted position, the rod antenna is mostly, or completely, located within the housing of the radiotelephone, whereas when the radiotelephone operates with the rod antenna in the extended position, most, or all, of the rod antenna is pulled outside of the housing, thereby extending the helix antenna well away from the body of the radiotelephone. The antennas are configured to provide a ¼ wavelength electrical length when retracted and a ½ wavelength electrical length when extended in the low frequency (such as AMPS) band. A matching circuit is provided using known techniques to provide a selected impedence in the extended position. The tap point where the helical antenna is connected to the rod antenna is intermediate the ends of the helical antenna and is selected to provide a desired impedence in the high frequency (such as PCS) band.

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