Microfluidically frequency-reconfigurable self-quadruplexing antenna based on substrate integrated square-cavity

In this article, a novel concept of self-quadruplexing tunable antenna (SQTA) enabled by microfluidic channels is investigated. The operating channels are either filled with air or dielectric liquids to enable frequency tunability. The proposed SQTA is implemented on the substrate-integrated square-cavity (SISC). A swastika-shaped slot is milled on the top-surface of the SISC to create four quarter-mode resonators. The resonators are excited by four 50-omega microstrip lines to enable independent operating bands with self-quadruplexing properties. The working principle is validated by a custom-developed lumped-circuit model. The port isolations are better than 27 dB due to the orthogonal and off-centered port allocation. Subsequently, two microfluidic channels corresponding to each quarter-mode resonator are milled from bottom-surface of the cavity. These two channels are filled with liquids of various permittivity to achieve frequency tunability. As a proof-of-concept, a prototype of the proposed SQTA is fabricated and demonstrated experimentally. The fabricated SQTA operates at 4.05-4.56 GHz, 4.645-5.295 GHz, 5.45-6.325 GHz, and 6.19-7.265 GHz. The measured realized gains of the SQTA are 4.4-4.5 dBi, 4.5-4.6 dBi, 4.8-4.9 dBi, and 4.9-4.95 dBi.