A Balanced HTS Dual-Narrowband BPF Based on meta-HRRs With Highly Controllable Passbands

In this letter, a miniaturized fourth-order balanced high-temperature superconducting (HTS) dual-narrowband filter using meta-hairpin ring resonators (meta-HRRs) is proposed. By virtue of the introduced quasi-lumped interdigital capacitors, inductive spiraled and meandering structures, a miniaturized size and multiple electric and magnetic (EM) transmission paths are generated. Thus, based on the features of sub wavelength size, highly controllable differential-mode (DM) dual mode, and EM coupling of meta-HRRs, a balanced dual-narrowband filter with attractive common-mode (CM) rejection and two controllable transmission zeros (TZs) is designed. For proof of concept, the experimental results of balanced circuit using HTS technology centering at 2.153 and 2.389 GHz are in good agreement with simulations, which validate the practicality of design concept.