Design of miniature high-temperature superconducting quadruplexer with wide stopband suppression (vol 579, 1353735, 2020)

In this paper, a compact high temperature superconducting (HTS) multiplexer with improved out-of-band suppression and wide stopband attenuation is proposed. Each passband can be individually synthesized and conducted by using distributing coupling scheme without any additional matching network. The proposed quadruplexer is constructed by four sets of four order bandpass filters (BPFs) with compact interdigital hair pin resonators (CIHR). The employ of the CIHR brings dramatically size reduction and harmonic suppression for the quadruplexer. The implemented quadruplexer with compact circuit size (1.4 x 1.6 cm(2)) is operating at center frequencies of 2430/2530/2630/2730 MHz for S band application. The isolations of non-adjacent BPFs and center frequency ratios of BPFs can reach 42 dB and 1.03 respectively. For verification, the proposed quadruplexer is designed, fabricated on DBCO HTS film, and tested at a temperature of 77 K. The measured results agree well with simulation predictions which shows the upper stopband with suppression level of 42 dB can be extend up to 3.3 f(c1).