Noise figure measurement success lies in the details

Noise figure measurement involves signals both close to and at the thermal noise floor at ambient temperatures. An extraneous signal leaking in can easily create a significant error. This places the very highest demands on screening. Even if the device under test (DUT) has high gain and the output level to the noise figure meter is comfortably high, the level from the noise source to the DUT is critically sensitive. Protection is needed from both radiated and conducted sources of interference.