Compact ultra-narrowband superconducting filter using N-spiral resonator with open-loop secondary coupling structure
Tao Lin, Wei Bin, Guo Xubo, Li Hongcheng, Luo Chenjie, Cao Bisong, Jiang Linan
       

The coupling strengths between N-spiral resonators with and without OLSCSs as a function of the resonator center distance S.