A 35 GHz Digital Fractional- N PLL Frequency Synthesizer Based on Ring Oscillato

Abstract

A 3.5 GHz digital fractional- N PLL in 65 nm CMOS technology is presented that achieves phase noise and spurious tone performance comparable to those of a high-performance analog PLL. It is enabled by a new second-order frequency-to-digital con- verter that uses a dual-mode ring oscillator and digital logic in- stead of a charge pump and ADC. It also incorporates a new tech- n i q u et or e d u c ee x c e s sp h a s en o i s et h a tw o u l do t h e r w i s eb ec a u s e d by component mismatche