  A tunable dual-band inverted F antenna (IFA) is presented in this paper. By
placing a LC resonator on the radiating arm, dual-band characteristic is
achieved. Especially, the capacitor in the resonator is a tunable thin-film BST
capacitor, which has a 3.3:1 tuning ratio. The capacitance of the BST
capacitors can be tuned by an external DC bias voltage. By varying the
capacitance, both the lower band and the upper band of the IFA antenna can be
tuned. And the total bandwidth can cover six systems, i.e., GSM-850, GSM-900,
GPS, DCS, PCS, and UMTS.
