A novel multiband modified planar inverted-F antenna (PIFA) with a compact single feed is proposed, which covers GSM900 (880-960 MHz), DCS (1710-1880 MHz), PCS (1850-1990 MHz), UMTS (1920-2170 MHz), Bluetooth/WLAN (2400-2480 MHz), WiMAX (2500-2690 MHz), HiperLAN/2 (5470-5725 MHz), and an additional band (4600-4800 MHz). In conventional PIFA, most of time the shorted pin acts as a capacitor load only for impedance matching purpose, which may yield a large ground plane, narrow bandwidth, and large antenna volume due to a long shorted pin to provide enough capacitance. In our design, the shorted pin just acts a short-circuited load, which is an effective way to control the current resonant paths and is a novel way in design a multiband PIFA. Furthermore, with this design and parasitic folded structures, the proposed multiband antenna can be modeled by parallel short-circuited transmission line impedance transformers (TLIT), which can easily create six mentioned frequency bands (from PCS band to HiperLAN/2 band) by adjusting the lengths of folded branches. Measurement result conforms that our multiband design not only provides size reduction of both the antenna and the ground plane but also enhances the bandwidth of the six bands.