A reduction in phase noise by 13 dB has been obtained over a previous 60-MHz surface-micromachined micromechanical resonator oscillator 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. Specifically, a mechanically-coupled array of nine 60-MHz wine-glass disk resonators embedded in a positive feedback loop with a custom-designed, single-stage, zero-phase-shift sustaining amplifier achieves a phase noise of -123 dBc/Hz at 1 kHz offset and -136 dBc/Hz at far-from-carrier offsets. When divided down to 10 MHz, this effectively corresponds to -138 dBc/Hz at 1 kHz offset and -151 dBc/Hz at far from carrier offset, which represent 13 dB and 4 dB improvements over recently published work on surface-micromachined resonator oscillators, and also now beat stringent GSM phase noise requirements by 8 dB and 1 dB, respectively.
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