The design and experimental demonstrations of a planar inverted-F antenna (PIFA) are presented. The physical parameters of the antenna, including shorting plate width, antenna input impedance, antenna thickness and ground plane dimensions, are studied. The influence of various parameters on antenna characteristics has been investigated using simulation software IE3D and experimental results. Comparisons with measured results on fabricated antenna structures are provided for simulation validation. Simple semi-empirical formulas of the operational frequency and input impedance on the antenna have also been obtained. These results are very useful in the design of PIFA.