The effects of a ground shield on the characteristics and performance of spiral inductors

The frequency dependence of the model parameters of patterned ground shield (PGS) inductors in large part is explained as a consequence of modeling a distributed system with a lumped model. The effects of PGS shape and material on inductor characteristics have been examined and explained. There is an optimum area for a PGS to maximize Q. Using an n/sup +/ buried/n-well PGS, the peak Q is improved by /spl sim/25% from that of an inductor without a PGS while only slightly changing L and C/sub p/ in comparison to inductors with other PGSs. Having a PGS does not significantly improve isolation between adjacent inductors when isolation is limited by magnetic coupling since a PGS is specifically designed to limit termination of magnetic fields.