Figure of Merit Associated with a Variable-Parameter One-Port for RF Switching and Modulation

Abstract

A universal definition of "figure of merit" associated with a variable-parameter one-part device (for example, a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-i-n</tex> diode) for RF switching or modulation is discussed. The definition of figure of merit applies to a variable-parameter, passive, and linear one-port which has two "quantized states" at a single specified frequency. The definition is based on a property of a variable-parameter one-port device which is invariant under arbitrary lossless reciprocal transformations. From the physical meaning of a figure of merit, any variableparameter one-port which has two "quantized states" can be transformed by a lossless reciprocal two-port network into a "canonical form," i.e., a variable resistance, which is equal to a reference resistance, say <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1\Omega</tex> , at one state, and equal to another resistance, say <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R \Omega</tex> , at the other state. This fact has brought great simplification in the analysis of a modulator or switch circuit which contains a variable-parameter one-port with two quantized states. A generalized transmission-type modulator and switch, generalized reflection-type modulator and a phase switch are studied, and the optimum modulator or switch characteristics of those networks employing one variable-parameter one-port device have been disclosed.