A 5th subharmonic, inverter-based injection locked oscillator with 72–83GHz locking range

This paper presents a 79GHz fifth subharmonic injection locked oscillator (ILO). Compared to classical ILOs which are based on the nonlinearity of coupling transistors, this work uses inverter chains for input pulse pre-shaping. Thanks to the harmonic rich square wave, the new ILO combines linear and nonlinear mechanisms which together widen the locking range. A prototype chip is fabricated in 28nm CMOS technology. A locking range from 72 to 83GHz is measured under -2dBm input power. The power consumption of the inverter chain, the core circuit and the output buffer is 9mA, 10mA and 9mA respectively. Besides, a peak detector is implemented to ensure the locked ILO operates near the free-running frequency where the output amplitude is higher.