A Chart for Analyzing Transmission-Line Filters from Input Impedance Characteristics

Filter calculations become difficult when network elements consist of transmission-line sections, since transcendental equations are involved. It is the purpose of this paper to describe the application of familiar impedance methods and Smith chart techniques which simplify many of these calculations. A chart is developed by means of which the most important characteristics of a filter may be read directly from a conventional input impedance curve plotted on a Smith chart. The principles involved in these methods are equally valid for all lossless filters consisting of identical and symmetrical sections, but are particularly well-suited for use with transmission-line circuits.