Suppression of spurious products in an electrostatic RF MEMS downconverter having differential drive and sense

Conventionally, a downconverter mixes and then filters out all except the required band. Using electrostatics for mixing signals produces unwanted frequency components due to the quadratic relationship. Consequently, this would require a high selectivity bandpass filter which would in turn impose a constraint on the bandwidth. In this paper, it is shown that by using a differential drive for an electrostatically actuated mixer, the unwanted frequency components are eliminated and the bandwidth-selectivity trade-off is relaxed. Simulation results show that with a Q factor as low as 11, the unwanted frequency content is cancelled and at the same time a bandwidth of 35 kHz is retained.