An innovative antenna radiation method for exciting a dipole-type radiation mode in the ground plane of mobile devices is proposed. This method is based on a capacitively loaded slot placed at the centre of the ground plane. The ground plane is 50 × 15 mm in length and width, respectively, which is the size typically used in USB dongles and headsets. The −10 dB impedance bandwidth is 12.9% at 2.4 GHz, fully covering the WiMax, Wi-Fi and Bluetooth frequency bands.

A loop-type ground antenna with wide-band operation is proposed for USB dongle applications. The solution for improving the bandwidth is based on a resonant feeding circuit that includes both an inductor and a capacitor. By choosing an appropriate ratio of the inductance to the capacitance, the impedance bandwidth (VSWR < 2) is 21.8% at 2.2 GHz, sufficient bandwidth to cover both the WCDMA and WiMax frequency bands.