5.5: Mixed-Mode Splitter/Combiner Smm = MSstdM-1

5.5 Mixed-Mode Splitter/Combiner S ^mm = MS ^std M ^-1

This section focuses on the development of a general purpose set of splitter/combiner matrix relationships. In the next section, a practical set of splitter/combiner specifications with an arbitrary phase offset term ( ?) are developed from these relationships. CMRR will be evaluated as a better amplitude/phase imbalance parameter metric for splitter/combiner components. Three additional parameters will also be introduced to represent the complete array of splitter/combiner specifications. These are the differential-mode-rejection ratio (DMRR), the response of differential-mode (RDM), and the response common-mode (RCM). Where DMRR is the inverse of CMRR and both qualities represent the rejection of an undesired mode component within a splitter/combiner. In addition, RDM and RCM represent the response of the differential or common mixed-mode signal applied to a combiner input.

The analysis begins by examining Figure 5.9 which shows a single-ended standard s-parameter flow diagram and establishes splitter/combiner port definitions. In Figure 5.9, port 1 is defined as the single-ended input or output, and the combination of single-ended ports 2 and 3 are defined as the mixed-mode port 2 input or output. The connections between the three single-ended ports define a basic RF signal transfer; single-ended signals are converted to and from a mixed-mode signal. This splitter or combiner circuit and is modeled with three single-ended port standard s-parameters shown in Figure 5.9 or with a hybrid single-ended/mixed-mode s-parameter flow diagram shown in Figure 5.10. Signal-flow diagrams are not a physically based representation of...