Shielding structures for millimeter-wave integrated transformers

Shielding structures intended to improve the performance of millimeter-wave transformers are presented. The loss mechanisms of the components are discussed and the losses related to the silicon substrate are shown to be the most relevant. A patterned ground shield and a floating shield are detailed and their influences in terms of inductance, quality-factors, coupling coefficients and minimum insertion loss are evaluated through measurement and electromagnetic simulations. Results indicate that quality-factors are deteriorated by the use of patterned ground shields, whereas the use of floating shields allows a slight improvement without degrading other characteristics of the transformer.