A high-temperature superconducting filter for future mobile telecommunication systems

This paper presents a narrow-band high-temperature superconducting bandpass filter on a sapphire substrate applicable to future mobile communications systems. The design and simulation of a ten-pole quasi-elliptic function filter implemented using a cascaded quadruplet trisection coupling topology is discussed. The filter is designed to have a 10-MHz passband in the Universal Mobile Telecommunications System base-station receive band. The filter substrate was a sapphire wafer measuring 47 mm ×17 mm ×43 mm, which had a double-sided thin-film coating of Yba₂Cu₃O₇. The filter displayed a minimum insertion loss of 0.2 dB in the passband and a return loss better than (-12dB preliminary) over the passband. A high performance out-of-band rejection associated with a quasi-elliptic filter function was also recorded.