Compact, narrow bandwidth, lumped element bandstop resonators

This letter describes the design and simulation of novel, highly compact, lumped element bandstop resonators. The resonators are fabricated using copper microstrip lines, with resonant frequencies around 5GHz but with areas of only 1.075mm × 1.275mm. Each resonator consists of 8 interdigital capacitive fingers in parallel with a straight line inductor. The new design offers at least a 40% size reduction compared with similar resonators , . Furthermore, adjustment of the input and output feed line geometries enables resonator tuning at the design stage over a bandwidth of approximately 100MHz. The measured characteristics show good agreement with the simulated responses. Ultimate performance of this type of bandstop resonator is achieved using superconducting thin films, and to conclude a 20-finger, superconducting resonator (of area 1mm × 0.41mm) is described and simulated.