S-band continuously-tunable slot-ring antennas for reconfigurable antenna array applications

This paper presents a continuously-tunable single-polarized slot-ring antenna operating at S band. The frequency tunability is achieved by loading the slot-ring antenna with varactors. By properly designing the feeding network and biasing circuits, the slot-ring antenna is able to cover 2-4 GHz. A prototype antenna was fabricated and measured. The measured return loss is better than 9 dB from 2.66 to 4.09 GHz. The antenna gain and radiation pattern are very close to simulation results. This tunable slot-ring antenna can be extended for a reconfigurable antenna array to cover both L band and S band by strategically placing switches and varactors inside the slots of the antenna. This novel antenna array is able to change its frequency, polarization and radiation pattern.