Compact wide stopband superconducting bandpass filter using modified spiral resonators with interdigital structure<xref rid="cpb_27_6_068502_fn1" ref-type="fn">*</xref><fn id="cpb_27_6_068502_fn1"><label>*</label><p>Project supported by the National Key Scientific Instrument and Equipment Development Project, China (Grant No. 2014YQ030975) and the National Natural Science Foundation of China (Grant Nos. 61371009 and 61401282).</p></fn>

Compact wide stopband superconducting bandpass filter using modified spiral resonators with interdigital structure**

Project supported by the National Key Scientific Instrument and Equipment Development Project, China (Grant No. 2014YQ030975) and the National Natural Science Foundation of China (Grant Nos. 61371009 and 61401282).

Wu Di¹, Wei Bin^{1, †}, Li Bo¹, Guo Xu-Bo¹, Lu Xin-Xiang², Cao Bi-Song¹

Sketch of the proposed resonator (not to scale) with potentials (+ and −) and current directions (arrowed) at (a) fundamental resonant frequency f and (b) first spurious frequency f_s.