A DIVERSITY ANTENNA FOR VERY SMALL 800-MHZ BAND PORTABLE TELEPHONES

A diversity antenna comprising a short whip antenna top loaded with a small cylinder and a new built-in antenna has been developed for very small portable telephones in the 800-MHz band. Wire-grid analyses and whip antenna experiments yielded good radiation characteristic results when the equivalent electrical length of the whip antenna equaled a h alf wavelength. The built-in antenna features extreme compactness, its size being one-third that of a conventional planar inverted-F antenna . The characteristics were investigated experimentally, and an antenna of 3.5 cc volume with a gain of -1 dBd and a bandwidth of 30 MHz was designed at 879 MHz. Finally, the diversity characteristics were subje cted to field measurements and a diversity correlation of 0.26 was obt ained.