A low phase noise InGaP-GaAs HBT transformer power combining VCO

A transformer-based power combining technique is shown to be an efficient method for reducing oscillator phase noise. Higher signal power can be achieved while avoiding breakdown without penalty in tuning range. An InGaP-GaAs HBT process was used to fabricate the 1GHz VCO. The measured phase noise at 100 KHz, 1 MHz and 3 MHz offset frequency is -116, -136 and -145dBc/Hz respectively. The VCO dissipates 3mW.