Tuning of Superconducting Filters With Laser Ablation Technique

Superconducting planar microwave filters manufactured without tuning functionality often do not rigorously agree with their specifications. This paper suggests a method for adjusting the center frequencies of microstrip superconducting filters without using tuning screws in the device packages. Trimming with laser ablation is judiciously used to change the resonant frequencies of cross open-loop resonators and thus adjust the center frequencies of filters. A technique for adjusting the interresonator coupling is also proposed.