A planar inverted-F antenna type tunable antenna with U-shaped slot is proposed. A varactor diode is integrated between the slot and bias feeding strip line for tuning the operating frequency. This antenna covers from 1.64GHz to 2.05 GHz refer to the dc bias voltage from OV to 20V. The frequency tuning range is about 410 MHz bandwidth which covers several mobile communication bands of DCS(1710 1880MHz), PCS(1750 1870MHz) and PCS(USA)(1850 1990MHz). This antenna occupies a compact volume of 40 × 15 × 8 mm3. The simulation result is based on the Finite Integral Method.