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This paper presents a differential VCO stacked with a divide-by-two to generate quadrature signals for low-power wireless applications. The transformer-based VCO core adopts the Armstrong VCO configuration to mitigate the small voltage headroom and the noise coupling. The operating conditions of the proposed quadrature local oscillator (LO) circuitry are derived based upon a linearized small-signal model. Also the phase noise performance is analyzed using a frequency-domain approach. The analytical results indicate that the mutual inductance and the quality factor of the primary coil play an important role in the trade-off between power and noise. The proposed LO was fabricated in 65 nm CMOS technology. The LO operates at 1.6 GHz under 1 V supply voltage and consumes only 2.6 mW of power. The measured phase noise is -140.3 dBc/Hz at 10 MHz offset frequency.
Circuits and Systems I: Regular Papers, IEEE Transactions on (Volume:59 , Issue: 12 )
Date of Publication: Dec. 2012