Читать книгу Handbook of Microwave Component Measurements - Joel P. Dunsmore - Страница 29

For very low noise figure devices, it is often convenient to express their noise factor or noise figure in terms of the excess power that would be at the input due to a higher temperature generator termination, which would result in the same available noise temperature at the output. This can be computed as

(1.65)

Thus, an ideal noiseless network would have a zero input noise temperature, and a 3 dB noise figure amplifier would have a 290 K excess input noise temperature, or 290 K above the reference temperature.