An IC-compatible, micro-electro-mechanical, down-conversion mixer-filter for use in reconfigurable integrated cell phones is introduced. Analytical and simulation models have been developed to enable mixer filter design. This device is composed of two high-Q, square-frame microresonators coupled by a soft flexural-mode micromechanical spring; and can be implemented using either thick epitaxial polysilicon technology or bulk micromachining of SOI wafers. The proposed mixer filter performs both frequency down-conversion (mixing) and highly selective low-loss filtering of applied electrical input signals. Using this single device, translation of an input radio frequency (RF) signal to a 71 MHz intermediate frequency (IF) and subsequent high-Q band-pass filtering at the IF with about 9.5 dB mixing conversion gain and 12.5 dB noise figure were demonstrated. One of the challenging issues that has hindered deployment of such micro-electromechanical devices is large motional resistance (Rx) of these devices with capacitive transduction. To lower motional resistance of the proposed mixerfilter (in order to provide convenient matching to preceding and subsequent blocks), we have exploited the motionless dimension of the device; i.e. we have increased height of the device and increased the overlap area in the input and output capacitive transducers to achieve that goal. Furthermore, the use of square-frame micro-resonators in the structure of the designed device, results in excellent isolation between Local Oscillator to Intermediate Frequency (LO-to-IF), LO-to-RF and RF-to-IF characteristics.

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