Design and experimental validation of highly miniaturized microfluidically frequency reconfigurable self-triplexing antenna with high isolation

This article presents a highly miniaturized frequency reconfigurable self-triplexing antenna with high isolation. The proposed antenna is constructed using two half-mode and one full-mode substrate-integrated cavities (SICs). The cavities are excited through microstrip feed lines loaded with slots to produce three fixed operating frequencies. Two methods are utilized to adjust these frequency bands. The initial approach involves adjusting the slot dimensions to fine-tune the individual frequency bands. This method provides frequency tuning ranges of 2.75-3.55 GHz, 4.3-6.3 GHz, and 5.42-8.05 GHz at lower, middle and upper-bands, respectively. Nonetheless, with each alteration in slot dimension, the proposed antenna must undergo fabrication and experimental validation, which is time consuming and costly. To address this issue, the frequency bands are reconfigured by utilizing microfluidic channels at the bottom of the cavities, which are filled with dielectric liquids. This technique provides frequency tuning ranges of 2.55-2.86 GHz for the lower band, 3.99-4.6 GHz for the middle band, and 5.2-5.89 GHz for the upper band, respectively. This technique also eliminates the need for additional fabrication. Using slot-loaded half-mode cavities and the channels offers a highly miniaturized footprint and high isolation. An equivalent circuit is developed to analyze the proposed antenna. To validate the design, an antenna prototype is fabricated and experimentally demonstrated. The antenna occupies a small area of 0.079λ_g² with high isolation of 33.2 dB. Furthermore, it exhibits frequency tuning within the ranges 2.55-2.86 GHz, 3.99-4.6 GHz, and 5.2-5.89 GHz using both the techniques with realized gain varying from 2.4 dBi to 5.65 dBi. Good alignment is observed between full-wave simulation and measurements.