Dual-Band VCO Using High Quality Factor Two Orthogonally Located Inductors in 0.18-μm CMOS Technology

This work introduces a new topology for designing low-phase noise (PN) dual-band voltage-controlled oscillator (VCO) by proposing orthogonally located inductors in 0.18- $\mu \text{m}$ CMOS. The inductors are implemented using five metal layers keeping the lowest layer empty to maximize the quality ( $Q$ ) factor. The first inductor is two halves shunted octagonal loops using the top layer (M6) and utilized in cross-coupled VCO, while the second inductor is formed by four C-shaped shunted inductors using the lower four layers $\text{M}_{\mathrm {5-2}}$ and used in current-reuse (CR) VCO. The M6 inductor improves the $Q$ -factor by more than 25%over one loop inductor in the frequency band of interest, while the $\text{M}_{\mathrm {5-2}}$ inductor uses four shunt layers to boost the $Q$ -factor by 28% in $K$ -band compared to the single-layer inductor. The VCO oscillates from 22.36 to 23.4 GHz with PN of −112.4 dBc/Hz at 1 MHz and figure of merit (FoM) of −188.8 dBc/Hz, while the CR VCO has tuning range from 23.8 to 25.7 GHz with a PN of −107 dBc/Hz at 1 MHz and FoM −185.8 dBc/Hz.