HIGH POWER HANDLING SUPERCONDUCTING PLANAR FILTERS FOR TELECOMMUNICATION APPLICATIONS

Passive microwave filters based on HTS films are very promising for telecommunication applications. We report on the design, obtained using a commercial 2.5D software, and the realization of filters, fabricated with double sided YBCO films grown on LaAlO 3 substrates, for both receiving and transmission systems. For the receiving side, planar multi-pole interdigital L-band filters with 75 MHz transmission bandwidths have been fabricated on 2" substrates. Up to 80 K this kind of filter, based on a Tchebischev response, shows an insertion loss lower than 0.5 dB with a ripple of 0.3 dB for a maximum input power of 2 Watts. For the transmitting side, dual-mode filters represent one of the main interesting configuration to exploit since they can combine a high power handling capability with miniaturization requirements. A novel kind of dual-mode C-band filter based on cross slotted square resonators is presented. The novelty of the proposed structure is to use a pair of unequal crossed slots that are formed on a square patch resonator such that its structure size can be significantly reduced. A prototypal device operating at 3.7 GHz is fabricated with different type of couplings on 10 × 10 mm 2 LaAlO 3 substrate to showcase our proposal. The behavior of the filter as a function of the input power has been tested up to 2 Watts limited by the amplified power supply.