Generalized efficiency measure for an Above-IC multifilar transformer applied to multiport integrated passive devices

This paper formulates generalized transformer efficiency associated with the applications of Above-IC multifilar transformers to multiport integrated passive devices (IPDs). The formulation derives the power loss ratio for a multifilar transformer in multiport configuration based on a terminated microwave network and then leads to the expression of passive efficiency using the concept of power conservation. For demonstration, the S-parameters for several different types of three-port transformers have been measured to compute their passive efficiency and further predict the minimum available insertion loss of the three-port IPDs such as baluns and combiners that use these three-port transformers.