Differential VCO and passive frequency doubler in 0.18 /spl mu/m CMOS for 24 GHz applications

Circuits for generating a 24 GHz LO signal indirectly using a 12 GHz VCO cascaded with a 2times passive mixer and directly from a standalone 24 GHz VCO are compared. Both circuits are implemented in 0.18 mum CMOS. The 24 GHz designs exhibit equivalent phase noise, but the use of a passive mixer enables a 4times reduction in power consumption and a 2times increase in tuning range compared to the standalone 24 GHz VCO. The VCO/mixer combination shows phase noise of -99.94dBc/Hz @ 1 MHz offset from the 25.1 GHz carrier, 12% tuning range, and 11 mW of power consumption