A 16.5–53.5 GHz Magnetically Tuned Transformer-Based Mode-Switching Injection-Locked Frequency Divider With 105.7% Locking Range

This letter presents a 16.5–53.5 GHz magnetically tuned transformer-based mode-switching injection-locked frequency divider (ILFD) in 65-nm CMOS. The fourth-order resonant tank of the proposed ILFD incorporates a switchable inductor coil along with a switchable capacitor to achieve mode-switching, effectively realizing a wide locking range (LR) compared to that of a conventional eighth-order transformer, while maintaining a high input impedance. Additionally, peaking inductors are utilized to ensure start-up conditions and achieve low power consumption. The measured LR and relative bandwidth are 37 GHz and 105.7%, respectively. The chip features a compact core area of 0.04 mm² and consumes 1.62 mW from a 0.45 V supply, resulting in figure of merits (FoMs) of 22.8 GHz/mW and 65.2%/mW.