A 0.06mm2 14.7-to-20.2GHz Quad-Core VCO Enabled by the Folded Circular Transformer Achieving 201.1dBc/Hz FoMT and 203.4dBc/Hz FoMA

This paper proposes a quad-core oscillator utilizing a folded circular transformer that utilizes both magnetic and electric coupling for core synchronization, greatly reducing the area and phase noise penalty of quad-core VCOs. Moreover, the proposed transformer simultaneously enhances common-mode and differential-mode quality factors. Fabricated in 28nm CMOS, the proposed VCO covers 14.7-to-20.2GHz (31.5%) within an area of $0.06 \text{mm}^{2}$ while consuming 5.3mW power. It achieves FoMA and FoMT@10MHz offset frequency of 203.4 and 201.1dBc/Hz at 15.8GHz.