On the performance of HTS microstrip quasi-elliptic function filters for mobile communications application

The low-loss and high-selective high-temperature superconducting (MTS) band pass filters can enhance performance of mobile communications systems, In t his paper, we summarize a recent progress of novel HTS preselect bandpass f ilters that have been developed for a European research project. The object ive of the project is to construct an MTS-based transceiver for mast-mounte d DCS1800 base stations. The MTS preselect receive filters have been design ed to have a quasi-elliptic function response in order to provide low inser tion loss and very steep rolloff at the filter band edges, The filters cove r a 15-MHz sub-band of a receive band, which ranges from 1710 to 1785 MHz, The filters have been fabricated using double-sided YBCO thin films on 0.3- mm-thick MgO or 0.5-mm-thick LAO substrates. The latest experimental result s of the filters, including those encapsulated with a low-noise amplifier i n an RF module are presented, showing very promising performance. The issue s associated with asymmetric frequency response are investigated to improve the filter performance.