Miniaturized Highly Selective Balanced Ultrawideband HTS Bandpass Filter Using CRLH Transmission Line Aided by Gray Wolf Algorithm

This is the authors' abstract. We don't add key points for this paper.

A balanced ultrawideband (UWB) high-temperature superconducting (HTS) bandpass filter (BPF) with miniaturized size and high selectivity is proposed based on a four-cell via-free CRLH-TL. The differential-mode (DM) and common-mode (CM) equivalent circuit models are established. The DM circuit operates as an eighth-order BPF with three transmission zeroes on the out-band while the CM circuit can get high CM suppression. The gray wolf algorithm (GWA) is used to derive the element values in the equivalent circuit models and then to optimize the physical parameters in the filter layout. Finally, the filter is fabricated and measured for verification with a size of0.17 × 0.43 ~λ gat the central frequency. Measured results show that the filter owns 0.2-dB maximum DM insertion loss, and minimum 18.3-dB return loss at a temperature of 20 K with a passband from 3.8 to 8.2 GHz. The selection factor (S.F) of the DM passband is 83.4%. The CM rejection is higher than 30.7 dB in the DM passband.