On automatic measurement of microwave noise figure

In conventional microwave automatic measurements of the amplifier noise figure, the measurement results are distorted by an error which is due to the noise of the receiver itself which is connected in cascade with the amplifier under test. This error depends on the receiver noise and on the gain of the amplifier. In the paper, there is presented a method which eliminates this error, and a setup is described which proves in practice the advantages of the method worked out. In the method, besides the two measurement states in which the noise generator is 'on' and 'off', there is included a third state, in which the receiver's own noise level is measured. This is enabled due to an electronically controlled microwave p-i-n diode switch, which does not affect overall accuracy.