A novel digitally controlled low noise ring oscillator

This paper presents a digitally controlled oscillator (DCO) with a novel architecture. The proposed DCO achieves low noise operation without the need for an LC resonator or specialized radio frequency (RF) process layers. Frequency tuning is achieved by controlling capacitive coupled charge injection. The design is easily integrated with digital CMOS circuits and has the flexibility to be scaled to other processes or tuned for specific applications. A proof of concept circuit has been implemented on a 0.13 mum CMOS process. The tuning range is from 820 MHz to 1.09 GHz. The phase noise at 1GHz with an offset frequency of 100 KHz is -92.8 dBc/Hz. The worst case cycle-to-cycle jitter is less than 1.28% with an RMS jitter of 1.7423 ps. Total power consumption is 6.12 mW.