ANTENNA DEVICE AND PORTABLE ELECTRONIC DEVICE COMPRISING SUCH AN ANTENNA DEVICE

摘要

An antenna device comprises a loop element (27) having a length (L1) providing loop resonance at a first wavelength, where a resonance frequency of this wavelength is used in a desired frequency band. A capacitance (28) is provided between a first position (P1) on the element and ground, thereby dividing the element into a first and a second section (S1, S2 ). The second section has an inductance that depends on the length (L2) and forms a resonance circuit with the capacitance which causes the element to function as a monopole element at the resonance frequency of the resonance circuit. The first position (P1) and capacitance (28) are so selected that the resonance circuit resonance frequency lies in the desired frequency band. The first position (P1) is also selected such that the length (L3) of the first section (S1) provides a monopole resonance at a second wavelength having one resonance frequency at the resonance circuit resonance frequency.