A Fully-Integrated 60-GHz Voltage-Controlled Oscillator Synchronized by Optoelectronic Signal

This paper presents a low-phase-noise frequency generator at 60 GHz deploying injection locking of a voltage-controlled oscillator (VCO) to an optical signal. The VCO is a Colpitts push-push oscillator, which is fundamentally locked to an external optical reference laser source. The chip is fabricated using IHP SG25H4 EPIC SiGe technology [1]. Operated from a 3.3-V supply and consuming a DC current of 80 mA, the VCO has a tuning range from 58.5 GHz to 65.7 GHz. At 58.5 GHz, the free-running VCO has a phase noise of -85 dBc/Hz at 1-MHz offset and it was reduced to -111 dBc/Hz under injection locking. This indicated a significant improvement in the phase noise performance of the VCO with optical injection-locking technique.