Low phase noise GaAs HBT VCO in Ka-band

Design and fabrication of a Ka-band voltage-controlled oscillator (VCO) using commercially available 1-mu m GaAs heterojunction bipolar transistor technology is presented. A fully differential common-emitter configuration with a symmetric capacitance with a symmetric inductance tank structure is employed to reduce the phase noise of the VCO, and a novel pi-feedback network is applied to compensate for the 180 degrees phase shift. The on-wafer test shows that the VCO exhibits a phase noise of -96.47 dBc/Hz at a 1 MHz offset and presents a tuning range from 28.312 to 28.695 GHz. The overall dc current consumption of the VCO is 18 mA with a supply voltage of 6 V. The chip area of the VCO is 0.7 x 0.7 mm(2).