Small percent bandwidth design of a 423-MHz notch-coupled micromechanical mixler

Notching and low-velocity coupling design strategies are described and demonstrated that yield the first UHF vibrating micromechanical hollow-disk ring mixer-filters with IF bandwidths down to 0.05%, while still retaining reasonable passband shapes. Specifically, a 423-MHz mixer-filter, comprised of two mechanically coupled resonators exhibiting Q's in excess of 10,000, has been successfully demonstrated with a flat passband bandwidth of only 202 kHz. Like a previous 34-MHz mixer-filter based on clamped-clamped beam resonators, the much higher frequency device of this work is capable of performing both mixing (via capacitive transducer nonlinearity) from an RF frequency down to its IF passband centered at 423 MHz, then very small percent bandwidth filtering, e.g., to remove unwanted interferers in the receive path of a communication handset. The percent bandwidths demonstrated here are small enough to make possible channel-selection much earlier in a receive path chain, which could then greatly enhance the robustness and battery lifetime of future wireless transceivers.