A 28-GHz–195-dB FoMA 3.72-GHz/V Class-B/C Nested-gm VCO With Coupled Tail Filtering in a 65-nm CMOS

This paper introduces a class-B/C nested-gm voltage-controlled oscillator (VCO) with coupled tail filtering in the 28 GHz band. The addition of only two cross-coupled NMOSs duplicates the gm to boost the transconductance. This topology exhibits the characteristics of coupled VCOs, such as when two VCOs are interconnected through a transformer. The core area is minimized by implementing a tail-filtering inductor for a secondary harmonic filter in same space with the primary transformer. The proposed VCO is fabricated with a 65-nm CMOS process, an output frequency of 25.4–29.12 GHz, and a
$K_{VCO}$
of 3.72 GHz/V. It has a supply voltage of 1 V and consumes 16.8 mW of power. It exhibits a phase noise of –105.34 dBc/Hz with a 1 MHz offset. The proposed VCO has a core area of 0.06 mm2. The figure of merit (FoM), FoM according to the area, and FoM according to
$K_{VCO}$
are –182.37, –194.96, and –192.66 dB, respectively.