  Microelectromechanical system (MEMS) based on-chip resonators offer great
potential for high frequency signal processing circuits like reference
oscillators and filters. This is due to their exceptional features like small
size, large frequency-quality factor product, integrability with CMOS ICs, low
power consumption, low cost batch fabrication etc. A capacitively transduced
cantilever beam resonator is one such popular MEMS resonator topology. In this
letter, the inherent square-law nonlinearity of the voltage-to-force transfer
function of a cantilever resonator's capacitive transducer has been employed
for the realization of frequency doubling effect. Using this concept, frequency
doubling of input signals of 500 kHz to 1 MHz, and 227.5 kHz to 455 kHz has
been experimentally demonstrated for two cantilever beams of length 51.75 and
76.75 micrometer respectively. The MEMS cantilevers have been fabricated with
polysilicon using the PolyMUMPs surface micromachining process, and their
testing has been performed using Laser Doppler Vibrometry. The test results
obtained are in reasonable compliance with the analytical and CoventorWare
finite-element simulation results. The high efficiency demonstrated by the
cantilever frequency doubler makes it a promising choice for signal generation
at high frequencies.
