A 67.4–71.2-GHz nMOS-Only Complementary VCO With Buffer-Reused Feedback Technique

In this letter, a mm-wave nMOS-only complementary voltage-controlled oscillator (VCO) is proposed. By replacing the large-sized cross-coupled pMOS pair in the classical complementary VCO structure with smaller and faster nMOS pair employing buffer-reused feedback technique, the parasitic capacitance introduced by the pMOS pair is reduced and the resonant frequency is thus effectively increased. Meanwhile, the negative resistance compensation is enhanced by the feedback reused buffer and the power efficiency is thus improved. The VCO, implemented in 45-nm CMOS SOI technology, occupies an area of 0.038 mm2including the buffer and is tunable from 67.4 to 71.2 GHz. The optimum phase noise measured at 69.4 GHz is -94.4 dBc/Hz at 1-MHz offset. The VCO and buffer consume 4.5 mW from a 1-V supply.