Divide-by-2 Injection-Locked Frequency Divider Using 3-path Transformer-Coupled Resonator

This article proposes a wide-band divide-by-2 injection-locked frequency divider (ILFD) in the 0.18 μm CMOS process. The ILFD uses transformer-coupled resonator and the secondary inductor can be turned on/off by a MOSFET switch. The free-running ILFD oscillation frequency is tuneable via switch gate bias, and the resonator looks like a resistively tuned resonator. The secondary is made of a three-path inductor and the primary is made of a symmetric three-turn single-path inductor. The single-band-like locking range is from 4.9 GHz to 12.71 GHz at the power consumption of 8.72 mW and the locking range is from 6.1 GHz to 12.1 GHz at the power consumption of 2.6 mW. The circuit also shows two non-overlapped locking ranges, which is attributed to the transformer-based 4th order resonator. Overlapped locking range technique is used to design wide-band transformer-based ILFD.