A varactor-tuned substrate-integrated cavity-backed dumbbell slot antenna

A novel varactor-tuned substrate-integrated cavity-backed slot antenna with wide tunability range of resonant frequency is presented. Using four varactors mounted on a dumbbell shaped slot etched on the horizontal wall of a substrate-integrated rectangular cavity, operating frequency of the proposed antenna can be tuned from 5.5 GHz to 7.6GHz, preserving the radiation pattern over the entire tuning range. The antenna has a high radiation performance, low profile and low fabrication cost. The antenna needs no bias network. The maximum -10dB impedance bandwidth of the antenna was about 2% at the frequency of 7.6 GHz. Gain of the antenna was more than 5.5 dB which is almost constant over the tuning range. Front to back ratio (FTBR) was better than 11 dB. Full-wave analysis was used for the design of antenna and the fabricated prototype of the antenna was measured to confirm the simulation results. The measured results agree with simulations.