Tunable Ring Resonator Filter for Duplexer

This paper proposes a novel ring resonator filter that has tunable capabilities for the center frequency, bandwidth, and out-of-band characteristic. The filter comprises ring resonators, switches, and tunable reactive elements such as varactors and tunable stubs. The newly proposed ring resonator incorporates varactors and switches that are connected to tunable elements. The varactors are used to change the center frequency. The point of the proposed filter is that the bandwidth can be varied without varying the center frequency, and the tunable elements make the skirt characteristics near the center frequency to be asymmetric with respect to the center frequency, which is suitable for constructing duplexers.