Perturbation Element Effect on Frequency Stability in Dual Mode Reconfigurable Filters Based on Circular Microstrip Ring Resonators

A detailed study about the suitable perturbation element shape and location for tunable BW dual mode microstrip filter which has circular ring resonator is presented. tuning achieved by geometry modification. The explains effect of                       a on stability of center frequency during tuning. Different cases have been studied two shapes element; one rectangular other radial. treated discuss whether located in inner or outer circumference ring, it patch notch. simulation case increase three times. best modeled, simulated, fabricated at 2.4 GHz. Geometry modification took into account RF MEMS modeling. an elliptic response, its FBW increased five steps from 1.7% to 5%. designed filters were evaluated experimentally    by with very good agreement.