Novel Microfluidically Tunable Differential Dual-Mode Patch Filter

This letter presents a novel microfluidcally tunable differential bandpass filter (BPF) with precisely controlled passband frequency. The frequency tunability of the filter is realized by inserting microfluidic channels, which can be filled with high dielectric constant fluid, i.e., distilled water, between the dual-mode patch resonator and the ground plane. Meanwhile, the frequency-tuning capability of the channels highly depends on the E-field distributions of the two modes on the patch. By properly choosing the orientations and spaces of the channels, the two-mode resonant frequencies can be simultaneously shifted up/down, and thus the frequency tuning states of the differential-mode passband can be precisely controlled with proper water-filling sequence. For demonstration, the proposed BPF is designed and fabricated. The simulated and measured results are presented, showing good agreement.