Frequency-agile, miniaturized slot antenna for hand-held devices

In this paper, a frequency-agile, miniaturized slot antenna suitable for use in hand-held devices is proposed. First of all, in order to design an electrically short slot, one end of the slot is terminated by a capacitance chosen according to a simple resonator model. The design concept is verified by both simulation and experiment, and is shown to be feasible. Instead of a constant capacitive termination, the frequency agility is attained by utilizing a varactor diode, of which the capacitance can be controlled by changing its bias voltage. A prototype antenna having a slot length of 20 mm and terminated by a varactor diode exhibits a continuously tunable resonant frequency between 0.78 GHz and 2.09 GHz as the bias voltage is adjusted from 0 V to 20 V.