Recent progress in miniaturized and reconfigurable filters for advanced communications and space applications

Innovative concepts are presented for both miniaturized high-selectivity and MEMS-based reconfigurable waveguide filters recently developed. The aim is to reduce size and weight of satellite telecommunication systems without compromising the high unloaded Q required in such applications. A first class of new miniaturized filters is based on ridges arbitrarily located and oriented within a waveguide. The ridges behave as quasi-TEM resonators and allow for pseudo-elliptic filter responses. A second class of very compact waveguide filters employs TM dual-mode cavities as building blocks to generate N^th order filters with N transmission zeros. Two new concepts have then been developed for high-Q bandpass filters with tunable central frequency or bandwidth using RF MEMS. Cantilever MEMS switches are suitably arranged in a rectangular waveguide so as to change either the TE₁₀₁ mode resonant frequency or the coupling between E-plane filter resonators. Both approaches are shown to yield higher unloaded Q (~1000) than previous approaches involving RF MEMS along with ridged or conductor-loaded cavities.