High-Order Compact Superconducting Dual-Band Bandpass Filters for Radio Astronomy

A compact high-temperature superconducting 8-pole dual-band bandpass filter (DB-BPF) using shorted stub-loaded hairpin resonator with high selectivity was developed for radio astronomy. Use of a pair of additional coupling elements between the resonators enable us to adjust the coupling coefficient flexibly. Tapped-line and coupled-line coupling was used for flexibly controlling the external Q factor of the first and second passbands. The center frequency of the first and second passbands are 0.8 and 2.0 GHz. The fabricated filter achieved high selectivity and compact size $\boldsymbol{(26.6\times 45.0}\ \mathbf{mm})$. The experimental results of the DB-BPF were in good agreement with the simulated ones.