Proposal and evaluation of reactively loaded inverted F antenna for cognitive wireless communication

In this paper, we propose a frequency-tunable compact antenna to enable cognitive wireless communication. Planar type inverted F antennas corresponding to some wireless service frequency bands are combined with a common feed rod. By loading variable diodes in the closed loops of each inverted F antenna, the reactance for each varactor diode can be controlled independently with DC voltage. We demonstrated an antenna design that achieved an impedance matching less than three for VSWR in the three frequency bands of the UHF band, the 1.92 - 2.17 GHz band, and the 5.15 - 5.35 GHz band.