On-chip interference suppression effect of S-shape inductor VCO

In this paper, a novel inductor with the S-shape layout is considered, designed and proposed to improve the drawbacks of the conventional spiral inductors. Due to the inherent feature of S-shape layout, the EM field distributions of the novel inductor are more constrained to the planar structure itself, rather than widely out-spread. The EM coupling effect through the substrate is thus relaxed. A testkey by integrating two VCO´s with a traditional spiral inductor and a proposed S-shape inductor respectively is implemented in a 0.18-mum CMOS technology to study the coupling effect. Also compared in this paper are the measured VCO circuit performances from the testkey.