Due to recent developments in wireless communications, frequency reconfigurable antennas have increased in popularity. This paper presents an integrated design for MIMO antennas that uses octagonal ring-shaped with a frequency-tunable dual-band reconfigurable for wireless communication applications. On the ground plane, the designed antenna has four octagonal ring-shaped radiators with a total size 50 x 50 x 1.6 mm3. In the center of each radiator, a varactor diode is employed to control the capacitive reactance of the slot to provide frequency reconfigurability. Between orthogonally positioned antennas, rectangular defective ground gaps are used for isolation purposes as well. Dual-band operation is achieved by linking the varactor to a slot line of radiating rings. The antenna's lower-frequency band resonates at 4.2 GHz, and its upper-frequency band can be tuned from 4.55 to 5.56 GHz (with isolation > 25 dB in the operating bands). The simulated results are found to be highly consistent with the experimental data. As a result, frequency agility, large tuning range, compactness, and planar structure make it appropriate for a wide range of existing and future wireless communication applications.
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