A 23-30.8 GHz Digital-Controlled-Oscillator in 28nm CMOS

A 19-bits digital-controlled-oscillator (DCO) in 28nm CMOS with a wide tuning range is presented. Four-staged switched capacitor banks provide the tuning to achieve 29% tuning range from 23 GHz to 30.8GHz. A new kind of capacitor design idea is introduced to achieve higher resolution of 38 kHz per step at 30.8 GHz and 11.2 kHz at 23 GHz. An extra pair of RC module is used to reduce the contribution of flicker noise from MOSFETs and help starting up the oscillator at lower frequency to extend the frequency tuning range. The phase noise are -104dBc/Hz@1MHz and -115.4dBc/Hz@5MHz when working at 24.5GHz with the power consumption of 7.1 mW.