Harmonic biasing in a double-sided comb-drive resonator, for resolving feed-through issues in low-power driving

We demonstrate a novel technique for operating a differentially-driven and differentially-sensed double sided comb-drive resonator. The resonator is driven by application of two out-of-phase ac signals to the drive stators, while the rotor is subjected to a pure harmonic signal at the same frequency as of the ac driving signals. In this mode of operation, no dc bias is necessary. This strategy results in two frequency mixing operations, such that a clear response can be sensed at the 3rd harmonic of the drive signal. Besides the responses in the 1st and 3rd harmonics of the drive frequency, no other higher-harmonic components are predicted from the analysis or observed in the measurements. With harmonic biasing, the resonator is insensitive to both feed-through currents that result from direct capacitive cross-coupling of sense and drive pads, and to feed-through currents that result from imbalanced sense ports due to packaging and setup. We show that a clear response can be achieved for low-power drive signals, whereas if the system were driven as a classic resonator with a dc bias on the rotor, the response would have been overshadowed by feed-through. We also demonstrate that the phase of the sensed response can be modified by varying the phase of the harmonic bias on the rotor. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

A novel technique for operating a double-sided comb-drive resonator was demonstrated in this study. By utilizing two out-of-phase ac signals on the drive stators and a pure harmonic signal on the rotor, two frequency mixing operations were achieved, resulting in a clear response at the 3rd harmonic of the drive signal. The resonator was shown to be insensitive to feed-through currents and imbalanced sense ports, and a clear response could be achieved for low-power drive signals.