Planar inverted-F antennas as an inverse class-F termination for wireless applications

We present an electrically small antenna for use with high-efficiency power amplifiers for wireless applications. A planar inverted-F antenna (PIFA) design is shown that is optimized to provide an inverse class-F load termination for use at the output of a field effect transistor (FET) for optimum output power and efficiency. A power-added efficiency in excess of 60% was also measured for an active PIFA.