US Patent 7391380 Telecommunication antenna

A telecommunication device has a permanently mounted antenna tuned to a predetermined resonant frequency and a housing formed of a plurality of parts one of which is removable. The one removable part, which may be an original element or an aftermarket add-on, changes the resonant frequency of the antenna when fitted to the housing. An electrically conductive passive correction element fixed in the one removable housing part is positioned therein and dimensioned such that when the one removable housing part is fitted to the housing the passive correction element cancels out the effect on the resonant frequency of the antenna by the one removable housing part.