Dual mode superconducting planar filters based on slotted square resonators

A new kind of dual-mode filter based on cross and transverse slotted square resonators is presented. A pair of unequal crossed slots formed on a squar e patch resonator provides both a reduction of the filter size and a simple and controllable way to couple the two degenerate modes. Transverse cuts o pportunely realized on the patch further decrease the operating frequency w ithout any appreciable change in the power handling capability of the devic e. Three examples of single stage filters operating in C-band with 1% and 1 0% fractional bandwidth are designed with a commercial 2.5D software and fa bricated using Nb and YBa2Cu3O7 films grown on LaAlO3 (100) substrates, The filters response is characterized at different temperatures and the insurg ence of non-linearity investigated varying the input power and carrying out intermodulation measurements.