The use of the Smith chart in classical frequency response analysis of control systems

Because they are conformal maps of applicable equations, and because of the geometric properties of those maps, Smith charts can be used to represent the complex-valued plots of the frequency response of both the open- and closed-loop gains of a single-input single-output system on the same graph, inside the unit circle. The plots thus obtained may be used, often better than polar plots or Nichols charts, in any classical frequency response design or analysis procedure of which the author is aware, and present many advantages.