Ultrawide Stopband Superconducting Filters With Multiple Harmonics Suppression

Multiple harmonics are suppressed by reduced external couplings and a symmetrical layout. The reduced external couplings are implemented by employing dual-hairpin resonators that simultaneously cancel the electric and magnetic fields. The symmetrical layout is utilized to additionally eliminate the spurious modes of substructure resonators. For validation, an eight-order superconducting filter incorporating two groups of stagger-tuned dual-hairpin resonators is designed and fabricated. The filter demonstrates excellent harmonic rejection suppressing six harmonics, extending the stopband to 17.4 f ₀ with a rejection of 60 dB, highlighting straightforward synthesis and compact size (0.206 λ_g × 0.046 λ_g ) _.