Planar frequency-tunable quad-band antenna with independently controllable bands

A low-profile quad-band loaded-slot antenna with independently controllable frequency bands is presented in this paper. Four slots are carefully designed to generate four separate frequency resonances, which were independently tuned by employing varactor diodes in each slot. The proposed concept was simulated using a full-wave solver and validated through measurements. The results show that each of the four bands can be independently controlled by altering the bias voltage of the respective varactor diode. Overall, the measured frequency tuning of the 1st, 2nd, 3rd, and 4th bands were 450–750 MHz, 600–1200 MHz, 1200–2100 MHz and 2100–2700 MHz, respectively. The proposed antenna has good potential for applications in the concurrently tunable multiband radio systems, including 5G.