The Influence of The Silver Film on The Electrical Properties of The Tunable Filter

A kind of tunable comb-line filter is studied and analyzed to save cost and get proper electrical properties. A varactor with capacitance which could be adjusted in a wide range is chosen to meet the frequency tuning requirement and the electrical properties including return loss and insertion loss of the tunable filter with different thickness of silver on the surface of the resonant inductor is presented. It is found that the electrically properties of the filter are only affected by the conductivity of the metal on the surface of the resonant inductor and the material inside the resonant inductor has few influences on the properties of the filter.