Tunable, Low Mass, Low Loss, Millimeter Wave, MEMS RF Filters

The feasibility of producing robust miniaturized, broadly tunable mm-wave bandpass filters for space applications is discussed. Current work by the authors has demonstrated very high-Q, broadly tunable "Octave+T" resonators in the 1.2 Ghz to 5.0 Ghz frequency ranges. These resonators have been designed using low-risk, conventional fabrication techniques that are ideally suited to making mm- to cm-sized ultra-high precision devices. At mm-wave frequencies, these resonators can best be described as tunable foreshortened coaxial resonators. The proposed mm-wave devices will have an unloaded Q of up to 2000 and full-octave tuning ranges, for example from 25 to 50 Ghz, although any full-octave tuning range up to the limitations of the packaging and interconnections can be constructed. In their present S-band configuration, Aesop's Octave+ resonators have been used to stabilize a broadly-tunable oscillator with phase noise of -132 dBc/Hz at 100 kHz offset, with a center frequency tunable from 1.2-2.6 Ghz, and a tuning speed of 1 Ghz/ms. In another configuration, three resonators were fabricated in a capacitively coupled arrangement to make a 25 Mhz bandwidth 3-pole 1.5-2.4 Ghz tunable preselect filter with 2.8 dB passband insertion loss. Aesop, Inc.'s resonators represent a proven, significant improvement over the state of the art in MEMS tunable resonator technology, combining resonator Q's of 400 and higher, octave tuning ranges, small size, low power requirements and low mass.