Noise figure measurement uncertainty caused by low gain of the two-port under test

The methods for direct-reading noise figure measurements of a low-gain two-port under test (TUT) are briefly described. Measurement error caused by the component dependent on the low gain of the TUT is discussed for the conventional noise figure measurement method, and for methods with elimination of the influence on indicator readings of the receiver noise figure as well as of both the receiver noise figure and the TUT gain. Generalized suppression for the measurement error caused by a low gain of the TUT, while different methods are used, is presented in the paper. The TUT's gain measurement by means of automatic noise figure meters is presented. A problem exists in such a measurement for the purpose of automatic correction of the noise figure measurement results, because only an insertion gain instead of an available gain can be measured.