Analysis and Design of a 0.6 V 2.2 mW 58.5-to-72.9 GHz Divide-by-4 Injection-Locked Frequency Divider With Harmonic Boosting

A locking-range enhancement technique is proposed for divide-by-4 injection-locked frequency dividers (ILFDs) at millimeter-wave frequencies. The working principle of the conventional divide-by-4 ILFDs is analyzed and verified with simulations to show that the limited locking range is mainly attributed to low efficiency of harmonic mixing. Based on the observation, an enhancement technique is developed by employing a properly-designed 4th-order LC tank to boost the 3rd-order harmonic tone at the output to increase the injection efficiency and thus the locking range. Implemented in a 65-nm CMOS process, a divide-by-4 ILFD prototype with the proposed harmonic boosting technique measures a locking range of 21.9% from 58.53 GHz to 72.92 GHz while consuming 2.2 mW from a 0.6 V supply, which corresponds to FoM of 6.54.