A 14-Pole Dual-Band High Temperature Superconducting Filter Including Narrow Bandstop Notches

This paper presents a 14-pole dual-band high selective high temperature superconducting (HTS) filter including two narrow notches. A flexible half-wavelength resonator, two cross-coupling structures and a novel feeding structure are proposed and analyzed successively. The HTS filter is fabricated on a 2-inch-diameter double-side DyBa2Cu3O7 HTS thin film with a 0.5-mm-thick MgO substrate and measured with a low-temperature test system at 65 K. The measured results show that the filter has 1 dB passbands of 1363-1440 MHz and 1490-1566 MHz, respectively. The filter has two narrow notches with maximum notch depths of more than 30 dB. Due to the cross-coupling structures, five transmission zeroes are located at both sides of the two passbands, which further improve the selectivity of the filter. The measured results are in good agreement with the simulated ones.