An HTS microstrip equalizer for improving the group delay of an HTS filter forthird-generation communications

Abstract

This paper reports a high temperature superconducting (HTS) microstrip equalizer forimproving the flatness of the pass-band group delay of an HTS filter for third-generation(3G) communications. The HTS filter to be equalized is a ten-pole quasi-ellipticfunction filter with a bandwidth of 9.6 MHz centered at 1946.5 MHz. The one-portcoupled-resonator microstrip equalizers were designed to have three or four poles, andthe calculated and simulated group delay response curves of the filter with theequalizers are presented and discussed. A three-pole equalizer was fabricated on apiece of 0.5 mm thick MgO wafer with double-sided YBCO films. The measuredresponses show that after connecting with the HTS equalizer, the group-delayeffective bandwidth of the filter, defined as the ratio between the flat group delaypass-band width (a criterion of variation of pass-band group delay being less than50 ns was applied) and the equal ripple pass-band width, increased from 50% to70% without any noticeable degradation of the band-edge steepness of the HTSfilter.