A varactor-tuned dual-band slot antenna

A new technique for designing dual-band reconfigurable slot antennas is introduced. The technique is based on loading a slot antenna with a lumped capacitor (or varactor) at a certain location along the slot. Given a fixed capacitor location along the slot, decreasing the capacitance results in increasing the first and second resonant frequencies of the slot antenna. However, the changes in the resonant frequencies are significantly different for the first and second resonances and, hence, a dual-band antenna with considerable frequency ratio tuning range can be obtained. Based on this technique, an electronically tunable dual-band antenna with a frequency ratio in the range of 1.2-1.65 is designed and fabricated using a single varactor with a capacitance range of 0.5-2.2 pF. The antenna has similar radiation patterns with low cross-polarization levels at both bands and across the entire tunable frequency range.