A 5GHz CMOS low phase noise transformer power combining VCO

A transformer based power combining technique is shown to be an efficient method for reducing VCO phase noise. Higher signal power and resonator Q can be achieved while avoiding breakdown without penalty in tuning range. A CMOS process was used to fabricate the 5GHz VCO. This VCO has a 4dB improvement in phase noise and 2dB improvement in FOM over a simple LC VCO. The phase noise at 1 MHz offset is -125 dBc/Hz. The VCO dissipates 5.5mA with 17.6% tuning range at a 1.5V supply voltage.