A 9–21.5 GHz Quad-Core Octa-Mode VCO With 202-dBc/Hz FoM _T at 1-MHz Offset in 28-nm CMOS Technology

This letter introduces a quad-core octa-mode voltage-controlled oscillator (VCO) in 28-nm bulk CMOS process. A novel reconfigurable <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> network is proposed, in which capacitive and inductive coupling paths jointly enable eight resonance modes. In particular, a center-tapped grounded capacitor allows capacitive participation under both even and odd modes. This design effectively doubles the number of available resonance modes to eight without increasing the number of cores and the chip area. Together with a mode-switching array, the VCO achieves a continuous tuning range (TR) of 82% from 9 to 21.5GHz and low phase noise down to −117 dBc/Hz at 1-MHz offset. The proposed VCO achieves a figure of merit with tuning (FoM<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${}_{\mathrm {T}}$</tex-math> </inline-formula>) of 202 dBc/Hz and occupies only 0.09 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, offering a highly efficient wideband solution.