Design of an Inductor-Less 72-GHz 2:1 CMOS CML Frequency Divider With Dual-Core VCO

This brief presents the modeling and design of a static current-mode logic, divide-by-2 frequency divider for mm-wave frequency synthesis. An optimized design procedure based on the $RC$ delay model and insights into the nonlinear mixing conversion gain of the injection-locking model are presented and leveraged towards the design of an inductor-less 28-nm CMOS prototype that achieves 72 GHz maximum input frequency and power-delay product of 21.5 fJ. Performance can be tuned to 66 GHz and 16.9 fJ, respectively, via lowering the supply voltage. In addition to standalone measurements with an off-chip input signal, a fundamental-frequency dual-core voltage-controlled oscillator provides on-chip and realistic input signal generation.