Statistical variations in VCO phase noise due to upconverted MOSFET 1/f noise

Statistical phase noise analysis and measurements are presented for a population of RF CMOS VCOs. The measured mean values for phase noise at 1 kHz and 1 MHz offset frequencies are -46 dBc/Hz and -130 dBc/Hz respectively. However a large variation from the mean (+/-3 dBc/Hz) is observed for the close-in phase noise. This variation is attributed to the upconverted transistor 1/f noise and its statistical nature. Phase noise simulations employing two versions of models with 1/f noise statistics have been run and compared to measurement. The improved noise model which accounts for the bias dependence of noise variability shows excellent agreement with measured data, while the early model with no bias dependence overpredicts the phase noise variations.