Active planar inverted-F antennas for wireless applications

We present an electrically small antenna for use with high efficiency power amplifiers for wireless applications. A planar inverted-F antenna design is described that can be optimized as a class-F termination for use as a load at the output of a field effect transistor (FET) for optimum output power and efficiency. An active planar inverted-F antenna is shown to have greater than 50% power-added efficiency at several frequencies between 1 GHz and 2 GHz by scaling the radiating element. These antennas are also shown to provide a copolarized field component in the azimuth plane and a cross-polarized field component in the elevation plane.