Novel miniaturized PIFA with interdigital coupling feed for multitband operation

A small size PIFA using intergidital coupling feed for internal mobile phone antenna application has been proposed and studied. The proposed PIFA is easily printed on the no-ground portion of the system circuit board of the mobile phone at lowcost and occupies a very small area of 400 mm² only, owing to the successful excitation of the mode as the fundamental resonant mode. The interdigital coupling feed greatly decreases the very large input impedance seen at the λ/4 mode for the traditional PIFA. The PIFA generates two wide operating bands at about 900 and 2100 MHz to cover GSM850/900 and GSM1800/1900/UMTS/WLAN operations, respectively. Good impedance matching of the two wide operating bands is achieved by using the interdigital coupling feed in the proposed PIFA.