New 20 GHz push–push common‐collector Colpitts VCO

Abstract

A wide-band push–push common-collector Colpitts voltage-controlled oscillator (VCO) usingimpedance peaking network and gain enhancing technique is proposed in this work.The impedance peaking network is introduced to increase the coupling factor ofthe differential inductor in the inductorcapacitor (LC) tank without sacrificing the quality factor. The impedancepeaking technique could guarantee the push–push VCO unconditionally oscillatingin a differential mode without degrading the phase noise performance. The gainenhancing technique employs an LC resonator in series with the emitterdegeneration resistor in the common-collector amplifier in the VCO core toimprove the VCO oscillating amplitude and then improve the phase noiseperformance. 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 to125°C. The measured phase noise is lower than −107 dBc/Hz at 1 MHz offset acrossthe entire working temperature (−40 125°C). The whole VCO dissipates 45 mA under3.3 V power supply, and the typical figure of merit is around −177.92.