Analysis and Design of a Double-Quadrature CMOS VCO for Subharmonic Mixing at Ka-Band

In this paper,we analyze the potentials of a four-phase 14-GHz CMOS voltage-controlled oscillator, tailored to a subharmonic receiver, for signal processing at -band. When mild phase accuracies between in-phase and quadrature down-converted signals are required, the four-phase oscillator displays roughly the same phase noise figure-of-merit as quadrature oscillator counterparts. However, the operation at half-frequency leads to an improved performance due to a higher quality factor of the tuning varactors, and because the local oscillator circuitry and signal path run at different frequencies, relaxing coupling issues. A detailed time-variant analysis of phase noise in multiphase oscillators is introduced and validated by both simulations and experiments. Prototypes realized in a 65-nm technology occupy an active area of 0.5mm2 and showthe following performances: a 26% frequency tuning range (from 12.2 to 15.9 GHz), maximum phase error from 4 of 2 , and a phase noise of 110 dBc/Hz at 1 MHz from 14 GHz, while consuming 18 mA from 0.8-V supply.