A V-band Differential SiGe VCO with varactor-less tuning

A SiGe V-band voltage-controlled oscillator (VCO) with varactor-less tuning is presented. The frequency tuning of the VCO is accomplished using the C_CB capacitance of the core transistors themselves. Removing the varactors within the VCO is particularly useful for millimeter-wave applications since varactors significantly degrade the quality factor of the resonator within the VCO and consequently the phase noise. This VCO utilizes a differential cross-coupled topology. The 67 GHz VCO was implemented in a commercial 180 nm SiGe BiCMOS platform and achieves a 6.7% tuning range and 0.3 dBm differential output power. The VCO achieves -90 dBC/Hz phase noise at 1 MHz offset from the 67 GHz signal.