Internal WWAN clamshell mobile phone antenna with reduced groundplane effects using a current trap

An internal WWAN antenna suitable for GSM850/900/1800/1900/UMTS operation in the clamshell mobile phone with reduced groundplane effects is presented. Small variations in the performances of the antenna in the open state and closed state are obtained. This is owing to the reduced effects of the upper ground plane on the performances of the internal antenna obtained by embedding a slit at the edge of the upper ground plane close to the connecting strip between the two ground planes of the clamshell mobile phone. In this case, large surface currents excited around the slit are achieved, with other portions of the upper ground plane showing much weaker surface current distributions, which makes the embedded slit behaves like a current trap for the excited surface currents.