Balanced Dual-Band Superconducting Filter Using Stepped-Impedance Resonators With High Band-to-Band Isolation and Wide Stopband

A balanced dual-band and wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF) with deep stopband rejection is designed using modified stepped impedance resonators (SIRs) in this brief. The center frequencies of the two differential-mode (DM) passbands can be controlled by adjus...

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Bibliographic Details
Published in:IEEE transactions on circuits and systems. II, Express briefs Express briefs, 2021-01, Vol.68 (1), p.131-135
Main Authors: Tang, Jiaming, Liu, Haiwen, Yang, Yang
Format: Article
Language:English
Subjects:
Attenuation
Balanced filter
Band-pass filters
Bandpass filters
Circuits
Dual band
high isolation
High-temperature superconductors
Impedance
Insertion loss
Resonant frequencies
Resonant frequency
Resonator filters
Resonators
Selectivity
stepped impedance resonator
Substrates
superconducting
Superconducting filters
Superconductivity
Thin films
wide stopband
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Summary:A balanced dual-band and wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF) with deep stopband rejection is designed using modified stepped impedance resonators (SIRs) in this brief. The center frequencies of the two differential-mode (DM) passbands can be controlled by adjusting two electrical length ratios of the proposed SIR, while keeping the third spurious frequency far away for wide-stopband design. An inherent common-mode (CM) suppression can also be obtained due to the discriminating CM resonant frequencies different from the DM ones. Multiple transmission zeros (TZs) are achieved to realize high passband selectivity and enhanced DM stopband by multipath coupling and shunt stubs loaded on the I/O ports. The proposed balanced dual-band filter operating at 1.78/4.0 GHz is eventually fabricated using HTS YBCO thin films on a MgO substrate, which can significantly lower the insertion losses. The circuit was measured at the temperature of 77 K, which shows maximum insertion losses of 0.42/0.37 dB and a DM stopband of 5.0f 1 d with 40-dB attenuation, respectively.
ISSN:1549-7747
1558-3791
DOI:10.1109/TCSII.2020.3001258