An improved Gm-boosted technique for a K-band cascode Colpitts CMOS VCO

This paper presents an improved g_m-boosted techniques for a K-band cascode Colpitts voltage controlled oscillator (VCO). This modified topology is derivative from conventional g_m-boosted technique by using cascoded cross-coupled pairs. By a quantitative small signal analysis, the g_m-boosted cascode Colpitts VCO increases its transconductance more than a factor of 0.5[1+(g_m1/g_m3)(1+C₁/C₂)]. A K-band VCO was designed to verify the concept. The measured central frequency of the designed VCO is 25.0 GHz with the tunable frequency range from 25.3 to 24.7 GHz. The core power consumption is 13.2 mW from a power supply of 1.5 V, and -103.1 dBc/Hz phase noise at 1 MHz offset. The maximum output power is -7.5 dBm. The calculated figure of merit (FoM) of this VCO is -180 dBc/Hz.