20-GHz quadrature injection-locked LC dividers with enhanced locking range

Quadrature injection-locked LC dividers with either a Miller topology or an injection-locked LC VCO topology are coupled with transconductors to enhance their locking range. The effect of the transconductance coupling is analyzed theoretically and through circuit simulation. Both topologies were fabricated by 90-nm CMOS technology with a target input center frequency of 20 GHz and output frequency of 10 GHz. The measured locking range for the Miller topology with transconductance coupling is 25.3%, compared to 20.9% without coupling. The measured locking range for the injection-locked LC VCO topology with transconductance coupling is 18.1%, compared to 12.9% without coupling. Moreover, power consumption for both dividers is 6.4 mW with a 1.2-V supply.