Mechanically-coupled micromechanical resonator arrays for improved phase noise
Seungbae Lee; Nguyen, C.T.-C.
Frequency Control Symposium and Exposition, 2004. Proceedings of the 2004 IEEE International
Volume , Issue , 23-27 Aug. 2004 Page(s): 144 - 150
Digital Object Identifier 10.1109/FREQ.2004.1418444
Summary:Reductions in phase noise by more than 26 dB have been obtained over previous micromechanical resonator oscillators by replacing the single resonator normally used in such oscillators with a mechanically coupled array of them to effectively raise the power handling ability of the frequency selective tank by a factor equal to the number of resonators used in the array, and all with virtually no increase in volume or cost, given that all resonators are integrated onto a single die using batch processed MEMS technology. Specifically, a mechanically coupled array of ten 15.4-MHz 40μm×10μm×2μm free-free beams embedded in a positive feedback loop with a single-ended to differential transimpedance sustaining amplifier achieves phase noise of -109 and -133 dBc/Hz at 1 kHz and far-from-carrier offset frequencies, respectively. When divided down to 10 MHz, these effectively correspond to -112 and -136 dBc/Hz, respectively, which represent more than 17 and 26 dB improvements over recently published work with clamped-clamped beam resonator oscillators.
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