CMOS-MEMS Filters

Silicon radio integration is currently limited by the ability to achieve high-Q filters on chip with the RF transistors. Furthermore, multi-terminal radio trends are driving the need for widely tunable filters. Progress on high-Q electrically-selectable CMOS-MEMS micromechanical filters and medium-Q widely tunable CMOS-MEMS LC filters is described. These filters are directly integrated from existing layers in foundry CMOS or BiCMOS processes and so may provide a manufacturable solution to future radio needs. Two LC filter topologies are described showing measured insertion loss as low as 5.1 dB and tuning range as high as 28%. The CMOS-MEMS micromechanical filters achieve Q of over 3000 at low pressure. Operation as an electromechanical mixer filter may lead to a compact on-chip solution for spectral power sensing for cognitive radio.