Noise figures (two-port linear transducers)

Abstract

In this paper, we present a short tutorial description of noise figures for two-port linear transducers and entire receiver systems. Due to the long history of the use of noise figures to specify noise performance, numerous definitions have evolved. The relationships between the various noise figure definitions found in the literature are specified in this paper and tables are provided as a cross reference to the notation and naming conventions used in the references.

Low-frequency noise in downscaled silicon transistors: Trends, theory and practice

“…where R s is the real component of Z s , and the noise voltage from the source is divided by 2, that is equally, between Z s and Z i at the matched condition Z i =Z s * . This reduction of reference power in RF noise figures to ¼ of thermal noise is clearly stated in [197], but rarely mentioned in recent publications.…”

“…where S in,avbl is the noise in the amplifier being referred as available power from signal source, S e =S in,avbl −S th,avbl is the excess noise added from the amplifier, also referred as available power from signal source, and T e =S e /k is the equivalent excess noise temperature, corresponding to S e . The standard reference temperature T o is 290K, and if the physical temperature is different, then a correction with ratio T/T o is made, as discussed in [197]. The excess noise ratio ENR, for example for noise sources, is given in respect to T o , and ENR=10dB×log10(S e /kT o )=10dB×log10(T e /290K).…”