Bandwidth enhancement techniques for planar inverted-F antenna

The planar inverted-F antenna (PIFA) is widely used in mobile radio systems because of its excellent performance. However, it is not yet employed as an ultra wide band (UWB) antenna because of its perceived narrowband characteristics. This study introduces three techniques for enhancing the impedance bandwidth of PIFA, which are (i) changes in the widths of feed plate and shorting plate, (ii) addition of an inverted-L-shaped parasitic element and (iii) addition of a rectangular parasitic element. It is shown that PIFAs with a very wide fractional bandwidths (up to 110%) can be achieved. Using these techniques, an UWB PIFA antenna is designed, manufactured and tested. Simulated and measured results are provided to verify the conclusion.