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This paper presents a 1.65-2.0 GHz digitally programmable oscillator. The oscillator is based on a MEMS resonator combined with a high-resolution 0.18 mum CMOS fractional-N PLL. Due to the dimensions of the MEMS resonator (350 mum times 130 mum), the size of the entire system is ~6.05 mm2, and can be integrated into a single small form factor package. The phase noise for an oscillation frequency of 1.8 GHz is -116 dBc/Hz at a 600 kHz offset, and the entire system consumes 50 mW from a 2 V supply. The PLL employs a 3rd-order 20-bit delta-sigma modulator to deliver an output resolution of ~220 Hz, i.e. enabling a controlled frequency stability of better than 0.125 ppm.
Date of Conference: 21-24 Sept. 2008