How can I tell if distortion is coming from test equipment (e.g. spectrum analyzer) or the DUT?
To determine if distortion is coming from the spectrum analyzer, increase the attenuator value at the front end of the analyzer and observe if the distortion decreases. If it does, then the distortion is being created at the spectrum analyzer. Make sure there is adequate bandpass filtering between the device under test and the spectrum analyzer. Another powerful test is to jump out the DUT and measure the distortion. Here the distortion should be well below the required distortion level. Typical distortion levels for Matrix equipment is well below –100 dB.
