An Eight-Port Frequency Reconfigurable MIMO Antenna Using Liquid Dielectrics

In this paper, an 8-port compact fluidic-based frequency reconfigurable MIMO antenna is designed and developed. The antenna employs eight modified U-shaped slots arranged in a 2 × 4 array on the top surface of a substrate integrated waveguide (SIW) cavity. Each slot is excited through a dedicated coaxial feedline. To achieve frequency reconfigurability, four fluidic microwells are integrated at the corners of each U-shaped slot. By filling the microwells with different liquid dielectrics (acetone, ethyl acetate, or distilled water) or air, the antenna’s resonant frequencies can be tuned. Additional reconfigurability is realized by selectively filling microwells with air and distilled water in various configurations. The proposed antenna demonstrates frequency agility from 1.29 GHz to 2.51 GHz. The measured results of the fabricated prototype show good agreement with simulated data. Furthermore, the antenna exhibits high inter-port isolation (>28 dB) in all configurations within a compact footprint of 0.114 λ2g. Peak gains of 4.75 dBi and 3.62 dBi are achieved when all microwells are filled with air and distilled water, at their respective resonant frequencies of 2.51 GHz and 1.29 GHz. The MIMO performance, evaluated in terms of diversity gain (DG) and envelope correlation coefficient (ECC), remains within acceptable limits, validating the effectiveness of the proposed design.