US Patent 7148849 Multi-band antenna

A multi-band antenna having a low frequency operating band and a high frequency operating band is provided. The multi-band antenna includes a radiating element, a grounding plane, a short-circuiting element and a short-circuiting regulator. The radiating element has a feed-in point for transmitting signals and several radiation arms. The first and the second radiation arms respectively have a first resonant mode and a second resonant mode which jointly generate a high frequency operating band, while the third radiation arm has a third resonant mode which generates a low frequency operating band. The grounding plane is connected to the radiating element via the short-circuiting element to miniaturize the scale of the antenna. The short-circuiting regulator of the grounding plane enhances the impedance matching when high frequency resonance occurs.