Compact Dual-polarized Reconfigurable MIMO Antenna Based on a Varactor Diode for 5G Mobile Terminal Applications

|With the rapid growth of wireless communication systems, there is a rising demand for multi-input multi-output (MIMO) antenna systems capable of adapting to various frequency bands and operating conditions. This paper presents an integrated design for MIMO antennas based on a varactor diode as a promising component for achieving frequency agility in the proposed system. A dual-polarized system is achieved by employing a combination of two antennas. One antenna is situated on the exterior surface of the side-edge frame, while the other is positioned on the substrate surface. The spatial con(cid:12)guration enables the creation of orthogonal polarization orientations, speci(cid:12)cally vertical and horizontal polarizations. In each element, varactor diodes are positioned to provide reactive loading. By incorporating varactor diodes with a variable bias voltage (0.5{10 V) into the antenna design, the resonant frequency can be dynamically adjusted, allowing the antenna to operate across a wide range of frequencies (4.3 to 6.5 GHz) with more than 18 dB of mutual coupling in the working band. The presented recon(cid:12)gurable antennas are printed on compact dimensions of 15 (cid:2) 25 (cid:2) 0 : 8 mm 3 using a Rogers RT5880 material with a relative dielectric constant 2.2. Because of its (cid:13)exible frequency range, extensive tuning range, small size, and planar structure, it is well-suited for various current and future wireless communication applications, including cognitive radio, software-de(cid:12)ned radio, and next-generation wireless networks.