A Wideband Injection Locked Quadrature Clock Generation and Distribution Technique for an Energy-Proportional 16–32 Gb/s Optical Receiver in 28 nm FDSOI CMOS

Abstract

We present a novel frequency tracking method that exploits the dynamics of injection locking in a quadrature ring oscillator to increase the effective locking range from 5% (7–7.4 GHz) to 90% (4–11 GHz). The quadrature phase error between I and Q phases of an injection locked ring oscillator is derived and shown to contain frequency error information, both inside and outside the locking range. This error is utilized to form a first-order frequency tracking quadrature locked loop (QLL). This loop generates accurate clock phases for a 4-channel parallel optical receiver using a forwarded clock at quarter-rate. The QLL drives an ILO at each channel without any repeaters for local quadrature clock generation. Each local ILO has deskew capability for phase alignment. The receiver maintains a constant energy-per-bit consumption across 16–32 Gb/s by adaptive body biasing in a 28 nm FDSOI technology.