Apparatus for measuring the noise parameters of a device under test (DUT), with full compensation for impedance mismatches between the DUT and the test apparatus. The apparatus includes an S-parameter measuring device, such as vector network analyzer (VNA), combined with a noise module. The noise module includes, among other things, a pair of test ports for the DUT, a noise source which can be turned on or off by an external controller, a receiver, and a switch for coupling the output of the DUT to selectably either the receiver or port 2 of the VNA.
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