Low phase noise 77 GHz VCO with optimized terminated impedance at fundamental and second harmonic frequencies

This paper describes the phase noise reduction technique by controlling terminal impedance of fundamental and second harmonic frequencies in VCO. To achieve low phase noise, the correlation between phase noise and second harmonic impedance in oscillator is investigated and two conditions to suppress phase noise are revealed. According to this investigation, a novel VCO is proposed to optimize the fundamental and second harmonic impedances. A fabricated VCO generating 77.0 GHz signal exhibits phase noise of −110 dBc/Hz at 1 MHz offset. To our knowledge, this is the lowest phase noise ever reported for W-band MMIC VCOs.