A 1∼1.5 GHz capacitive coupled inductor-less multi-ring oscillator with improved phase noise

This paper presents a multi-ring coupled oscillator design that employs the common-source capacitive coupling technique to achieve improved phase noise by minimizing noise injection from tail current and adjacent rings. The proposed inductor-less ring oscillator also provides additional output phases for low noise multiphase clock generation. Implemented in a 130 nm CMOS technology, the 1.5 GHz triple-ring coupled ring oscillator achieved measured phase noise of -110.17 dBc/Hz @ 1 MHz offset, demonstrating 7 dB phase noise reduction comparing to its single-ring oscillator counterpart.