Tunable resonator employing comb-shaped transmission line and switches

This paper presents a novel digital tunable resonator. It comprises a λ/4-length microstrip transmission line with a comb-shaped pattern on both sides of the line and multiple switches. Each switch is placed on the edge of two adjoining comb teeth to connect them to each other. The resonant frequency of the resonator can be changed by controlling the high frequency current path length using the switches. Electro-magnetic simulations are performed and the estimated tuning ratio is 22%. A prototype of the proposed resonator is fabricated to verify the feasibility, and the measured characteristics agree well with the simulated ones.