Compact multiband PIFA with a coupling feed for internal mobile phone antenna

A compact multiband PIFA (planar inverted‐F antenna) occupying a very small volume of less than 0.8 cm 3 in the mobile phone for GSM/DCS/PCS/UMTS operation is presented. The PIFA uses a single resonant path only, which is close to about one‐eighth wavelength at 900 MHz. A coupling feed, different from the conventional direct feed, is proposed to excite the PIFA. In this case, the large input impedance at 900 and 1900 MHz can be greatly decreased, making it promising to excite two operating bands at about 900 and 1900 MHz to cover the desired multiband operation. Good radiation characteristics for frequencies over the operating bands are also obtained. The occupied volume of the proposed multiband PIFA is about the smallest among the reported internal multiband mobile phone antennas.