Fair enough, looks as though I did miss your point.
I must confess to being rather skeptical myself - they look to be variations on FFTs which don't seem to suit measurements of noise, at least in my understanding. Added to that the ADC would need to be considerably better than the DAC being tested, or at least produce artifacts orthogonal to these being examined in the DAC. My own hunches lead me to consider that some kind of analog signal processing (passive filtering maybe) might be required prior to digitization for the dynamic range of the ADC not to be the bottleneck in measurement. Certainly this is already the case in very low level THD+N measurements of amplifiers.
mmm.... seen this before somewhere......
The point you are trying to make is that high level signals going into an ADC produce distortion in the ADC so you cannot be sure if the distortion / noise is in the source (DUT) or the measurement system. Hence -60 dB is usually used. So if you want to look at the noise floor in the presence of a high level signals its better to notch out the primary signal before it hits the ADC. Obviously you need to be very careful how you go about performing that filtering.
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