Divide-by-2 Injection-Locked Frequency Dividers with Twisted Inductors

This letter studies the RF performance of wideband divide-by-2 injection-locked frequency dividers (ILFDs) with various inductor layouts in the 0.18 µm CMOS process. The ILFDs use an inductor composite in shunt with parasitic capacitors as the resonator, and they also use capacitive cross-coupled pairs to generate negative resistance for start-up oscillation. The gate biases of capacitive cross-coupled pairs are used to tune the free-running ILFD oscillation frequency. The first designed ILFD uses two octagonal inductors, the inductors in other two ILFDs use a twisted configuration and the ILFDs have low EM radiation level and less sensitive to received EM noise. These ILFDs have wide locking range because no varactors is in shunt with injection FETs.