New 20 GHz push–push common-collector Colpitts VCO

A wide-band push–push common-collector Colpitts voltage-controlled oscillator (VCO) using impedance peaking network and gain enhancing technique is proposed in this work. The impedance peaking network is introduced to increase the coupling factor of the differential inductor in the inductor capacitor (LC) tank without sacrificing the quality factor. The impedance peaking technique could guarantee the push–push VCO unconditionally oscillating in a differential mode without degrading the phase noise performance. The gain enhancing technique employs an LC resonator in series with the emitter degeneration resistor in the common-collector amplifier in the VCO core to improve the VCO oscillating amplitude and then improve the phase noise performance. The proposed VCO oscillates at around 20 GHz with >10.5% frequency tuning range from 18.9 to 21.4 GHz across temperature from −40 to 125°C. The measured phase noise is lower than −107 dBc/Hz at 1 MHz offset across the entire working temperature (−40 125°C). The whole VCO dissipates 45 mA under 3.3 V power supply, and the typical figure of merit is around −177.92.