Characteristics of ultra-wideband bandpass YBCO filter with impendence stub
Journal
IEEE Transactions on Applied Superconductivity
Journal Volume
21
Journal Issue
3 PART 1
Pages
551-554
Date Issued
2011
Author(s)
Abstract
A compact ultra-wideband (UWB) bandpass filter (BPF) is presented for applications to short-range and high-speed wireless communication. Superconducting YBa 2 Cu 3 O y (YBCO) stepped impedance resonators and coupled-line sections as inverter circuits are designed to form the basic filter structure. In the filter design, connected high-low stepped impedance microstrip lines construct the resonators, and open-stub lines are utilized to add return-loss poles in the pass-band and create transmission zeros in the lower/upper stop-band region. Simulation results show that the passband from 3.0 GHz to 8.6 GHz has a 3-dB fractional bandwidth of 99 percent, computed insertion losses better than 0.03 dB, and return losses greater than 15 dB. Rejection levels in the upper/lower stop-bands are better than 20 dB. For fabrication, high-T c superconducting (HTS) YBCO films were deposited on double-side-polished 0.5-mm-thick MgO (100) substrates by a radio-frequency sputtering system. The filter was made out of patterned double-sided deposited YBCO films integrated with a gold-coated housing. The realized HTS UWB BPF shows a wide passband within 2.9-8.3 GHz with a maximum insertion loss of 0.88 dB. The measured results show good HTS UWB BPF performance. Moreover, the temperature-dependent frequency responses and the insertion loss can be described by the modified two-fluid-model-based formulas, indicating that the frequency shift and the increase in insertion loss for HTS BPF are both dominated by the temperature dependence of the magnetic penetration depth.
Type
conference paper