The Schrödinger equation and the equation describing the behavior of voltage on a transmission line are both linear second‐order equations, which may be solved by convenient matrix methods. By drawing analogies between these two problems, it is shown that a method used for antenna impedance matching based on the Smith chart corresponds in quantum mechanics to a simple conformal transformation of the logarithmic derivative of the wave function. One thereby can arrive at an elementary derivation of the Wentzel–Kramers–Brillouin quantization condition.

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