Implementation of New CMOS Differential Stacked Spiral Inductor for VCO Design

A new type of silicon-based differential stacked spiral inductor (DSSI) was proposed in this letter, which was successfully implemented in the design of a cross-coupled differential voltage-controlled oscillator (VCO). The samples of DSSI and VCO were fabricated using standard CMOS 0.18 mum process. Based on the two-port S-parameters measured using standard deembedding procedure, the self-resonance frequency (f_sr ) and -factor of the new and conventional DSSIs, frequency tuning range and phase noise of two VCOs are characterized and compared. It is demonstrated that, due to the reduction of parasitic capacitance in the new DSSI, its f_sr is increased significantly, and further resulting in the evident increase of frequency tuning range of the VCO with smaller on-chip area occupied, as compared to the other new VCO design.