A 13.6-17.7 GHz Sub-Harmonic Injection-Locked SSPLL with 74-fs RMS Jitter

This paper presents a sub-harmonic injection-locked sub-sampling PLL (SIL-SSPLL) that realizes a peaking-free jitter transfer. The use of an injection-locked oscillator (ILO) in SSPLL allows the PLL open-loop transfer function to achieve a higher phase margin, thereby enhancing the jitter performance. The study also analyzes the effects of injection locking strength on noise rejection for both the reference signal and the VCO showing that optimal jitter performance can be achieved by properly setting the injection strength. A 13.6 to 17.7 GHz SIL-SSPLL prototype fabricated in a 40 nm CMOS technology demonstrates 74 fs RMS integrated jitter at 15.8 GHz while consuming 22.6 mW of power, leading to an excellent figure of merit (FoM) of -249.1 dBc/Hz.