A novel fluidic-based phase reconfiguration technique using embedded slot-coupled transmission lines for X-band applications

This article presents a technique for phase reconfiguration in broadside-coupled microstrip transmission lines with in situ fluidic channels. Unlike conventional active phase tunable structures, the proposed design achieves phase tunability by dynamically modifying the effective permittivity of the substrate through controlled fluidic injection, eliminating the need for active components or complex biasing circuits. The design is compact (20 × 50 × 5.1 mm3) and offers a cost-effective solution by using deionized (DI) water as tuning fluid. The fabricated prototype operates at 10.5 GHz and achieves a maximum phase shift of 43.8° across five distinct phase states, with an insertion loss ranging from −2.65 to −4.92 dB. Experimental validation confirms the stability and reusability of the device, with negligible phase deviation after multiple tuning cycles. The proposed fluidic based phase reconfiguration technique is well-suited for applications in adaptive dielectric based fluid sensing, reconfigurable radio frequency (RF) circuits, and wireless structural health monitoring systems.