RF Design using Differential S-parameters for Wireless Modules

The evolution of semiconductor-based radios has allowed the rapid development of RF design both for wireless systems and wireless modules.  One advantage of semiconductor integration is the ability to realize various radio systems as differential circuits to maximize performance and yield. However, many wireless systems are single-ended at the front-end terminals. Regardless if the interface is single-ended or differential, it is important to understand the characteristics of a single differential RF port in terms of Mixed-Mode S-parameters in order to bridge the two disciplines of RF design engineering and semiconductor engineering.

Once a designer is aware of the mixed-mode technique in RF design, standard models can be developed and shared amongst RF designers and system designers, using a common base of definitions, terminology and design approaches.  This series of articles is prepared to provide incremental information in small pieces to provide a sufficient level of detail and provide conceptual closure without extensive and prolonged study.  The articles are intended to bridge pure engineering analysis techniques to practical RF design and product realization examples. 

This first article will address the most basic case of Mixed-Mode S-parameter RF design techniques: the characterization of a one-port network. Typically system designers will encounter this problem in that a semiconductor radio circuit will present a differential input port that needs to be matched and possibly converted from a differential to single-ended port.  Subsequent articles will address the matching procedure and expand this analysis to multi-port systems.