Broadband compact model for on-chip mm-wave transformers and baluns with emphasis on capacitive coupling effects

Distributed capacitive coupling effects in the transformers and baluns at millimeter-wave band are investigated in this paper and a lumped coupling branch with parameter estimation method is proposed. The accuracy near and beyond resonance frequency of the new equivalent circuit model is greatly improved. Different types of transformers and baluns with various geometries are fabricated by 0.13um RF CMOS process. The simulated results agree quite well with all the experiments in the whole measured regime up to 40GHz. And the proposed model is further validated by EM simulations up to 80GHz, indicating that it captures the physical essence behind correctly.