This paper presents a complementary metal-oxide-semiconductor (CMOS) differential voltage-controlled oscillator (VCO) implemented with the push-push principle. The push-push VCO uses two frequency doublers stacked in series with an LC quadrature voltage-controlled oscillator (QVCO) to share the dc current with the QVCO for low power consumption. The proposed CMOS VCO has been implemented with the TSMC 0.18 μm CMOS technology, and the die area is 0.822×1.564 mm2. At the supply voltage of 0.9 V, the total power consumption is 3.15 mW. The free-running frequency of VCO is tunable from 10 GHz to 11.15 GHz as the tuning voltage is varied from 0.0 V to 1.2 V. The measured phase noise at 1 MHz frequency offset is -114.93 dBc/Hz at the oscillation frequency of 9.99 GHz, and the figure of merit (FOM) of the proposed VCO is -190.0 dBc/Hz.
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