Decreased noise figure measurement uncertainty in Y factor method

Abstract. Almost always noise figure is measured today by using a matched noise source delivering two different but known noise temperatures (Y factor method). In commercially available noise sources these temperatures are characterized by the excess noise ratio (ENR) value, describing the ratio of equivalent noise power when switched on related to the noise power of a resistor at a temperature of 290 K (switched off). For a typical ENR value of 5 dB that means a hot temperature T_h=1207 K and a cold temperature T_c = 290 K.