On the Smith chart shown in Figure E9-3, what is the name for the large outer circle on which the reactance arcs terminate?

Explication

In Figure E9-3 every curved arc — those labeled 0.2, 0.5, 1.0, 2.0, 5.0 and 20 above and below the horizontal line — runs from the large outer circle inward to the point marked ∞ on the right. That outer boundary carries the reactance values and is called the reactance axis.