Higher order FFSFR coupled micromechanical mixer-filters integrated in CMOS

This paper demonstrates how micromechanical on-chip MEMS resonators can be used as higher-order mixer-filters in RF front-end WSN nodes. Vibrating FFSFRs (Free-free Square Frame Resonator) connected together can create 4th and 6th order mixer-filter responses. The output is further enhanced by an on-chip amplifier, thus reducing stray capacitances. These mixer-filters are fabricated utilizing a CMOS-MEMS approach where the movable MEMS structure is defined by the metal layers offered by the CMOS foundry and released using a few simple etch steps. The system is implemented in TSMC 0.35μm CMOS and was post-CMOS processed at NTHU in Taiwan. Detailed modeling, simulation and implementation of the system show the performance of these higher order MEMS resonator mixer-filters as a potential candidate to replace bulky off-chip transceiver components.