Simplified graphical analysis of linear three-port stability

The paper presents a simplified graphical analysis of linear three-port stability. Instead of the previously reported three conditions, only one plot of a single stability condition needs to be constructed in each termination reflection plane. The plot is useful to aptly depict the terminations at each port that result in unconditional stability between the remaining two ports. Such unconditional stability is ascertained using the single necessary and sufficient condition, which is expressed in a generalised form in terms of three-port S-parameters. The construction of three-port stability plots is delineated and exemplified to illustrate the convenience using the single condition. These stability plots find direct application in the stabilisation of potentially unstable networks.