High selectivity reconfigurable filters with controlled channel bandwidth

In this paper, we present the design of a novel class of reconfigurable filters allowing a control of bandwidth and maintaining a high Q in all configured states. The concept can be applied to any type of filters including planar, waveguide as well as FBAR filters. The proposed filters have the potential to replace large numbers of fixed filters by a single tunable design. The key idea is to combine high-Q un-tuned resonators with a set of tunable resonators. The selected bands can be controlled by proper placement of fixed transmission zeros generated by the high-Q resonators. The combination allows a highly selective filter response with flat pass-band for all states. Measurements on a planar microstrip filter verify the concept.