Multi-stage dual-mode cross-slotted superconducting filters for telecommunication application

Dual mode high temperature superconducting (HTS) filters represent an interesting device class for telecommunication application since they combine a high power handling capability with a miniaturized size. Here we report on the design and realization of dual mode cross slotted filters presenting a more compact size if compared with the traditional dual mode patch filters. Single stage filters operating in C-band with 1% fractional bandwidth have been designed and tested at prototype level by using double sided (YBa2Cu3O7-x) YBCO and Tl2Ba2Ca1Cu2O8 (Tl-2212) superconducting films grown on LaAlO3 substrates. The YBCO filter presents insertion losses IL=1dB and a power handling higher than 10dBm at T=77K while the Tl-2212 allows to operate at higher temperatures with comparable performances. Dual stage (four poles) and four stage (eight poles) filters with 1% fractional bandwidth operating in C-band and presenting a Chebychev or a quasi elliptical response have been analyzed. Finally, a four stage filter well fitting on a 1"x1" substrates was designed.