A novel HTS filter with improved out‐of‐band rejection by introducing a quarter‐wavelength spiral stub

Abstract

A novel high temperature superconducting (HTS) filter with split‐end stepped impedance resonators (SIR) is developed on MgO substrate. Spiral feedlines are used to meet the requirement of the external quality factor. A quarter‐wavelength (λ/4) spiral stub is introduced at the input feedline to provide additional transmission zeros at the high frequency end, which can improve both the out‐of‐band rejection and band‐edge steepness. The measured results at 70 K are in good agreement with the simulated ones. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2455–2457, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23688