Methods for direct-reading noise measurements of low-gain two-ports

This paper describes direct-reading measurement methods of noise figure F/sub m/ displayed by an automatic noise figure indicator. The F/sub m/ readings should be equal to F/sub x/, which are the true noise figure values of the two-port under test, regardless of its available power gain G/sub Ax/, and the noise figure of the measurement receiver F/sub t/. Technical problems of these F/sub x/ direct readings are shown. They particularly occur while using the conventional measurement methods. Methods that allow elimination of the influence of the F/sub r/ value on F/sub m/ readings as well as the influence of both F/sub r/ and G/sub ax/ on F/sub m/ are discussed. An important advantage of using the method with elimination of the F/sub r/ value is presented. Formulas are given which allow the estimation of the technical requirements for additional blocks of measurement systems or to count measurement error components, specific for the chosen measurement method.<
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