Design and performance of superconducting filter with a linear phase for CDMA2000 communication system

A high temperature superconducting （HTS） filter with a linear phase is designed for CDMA2000 communication systems. The principle and equivalent model of the filter have been presented. The theoretical result, coupling matrix, and the simulated result with Sonnet software have also been demonstrated. The desired filter with 12-pole and 2 cross couplings has a center frequency of 830 MHz. The measurement results show that the response of practical filters is in good agreement with that of simulated results and theoretical analysis, the group delay variation is less than ±10 ns over 60% of the filter bandwidth, and the skit slope of the filter is about 37 dB/MHz.