Performance Characterization of Circular Silicon Transformers

We have characterized performance of on-chip circular silicon transformers. The circular transformers were fabricated by the standard 0.18 mum CMOS process. We used measured two-port S-parameters, a de-embedding procedure, and simulated S-parameters derived from a lumped-element circuit model. We examined performance indicators of transformers such as quality factor (Q), maximum available gain (G _max), coupling coefficient (kappa), and minimum noise figure (NF _min) for various cases. We characterized all the parasitic capacitive and inductive effects. The results obtained are useful in the global optimization of high-performance transformers used in the design of certain radio-frequency integrated circuits.