A tunable dual-narrowband HTS filter using coding superconducting metamaterials aided by grey wolf algorithm

The design of tunable dual-narrowband high-temperature superconducting (HTS) filter based on coding superconducting metamaterials aided by grey wolf algorithm (GWA) is proposed in this paper. By virtue of the characteristics of right/left-handed bands and scale of deep sub-wavelength, the tunable metamaterials unit loaded with varactor is designed, with coupling types of coding pairs further studied. A tunable sixth-order HTS filter circuit is then constructed, whose layout is effectively optimized by newly developed GWA method. Simulated frequency responses demonstrate that the center frequencies of dual-band respectively locate at 170.1–177.2 MHz (Band I) and 185.2–194.1 MHz (Band II), with 3 dB fractional bandwidth of 0.65%–0.61% and 0.62%–0.57%. The deeply miniaturized circuit size is 0.037 × 0.046 λ2g, and the close-to-band rejection level reaches 80 dB. Experimental results of fabricated prototype measured at 70 K validate the feasibility of described design method for high order tunable HTS filter.