It is important to understand that quantization noise is equally distributed over the whole generation bandwidth. This means that an ideal 8-bit AWG running at 9GSa/s generates the same quantization noise spectral density than a 10-bit 650MSa/s AWG while offering 16 times more usable bandwidth. However, the 8-bit sample resolution spec is only valid when the generator is to generate a wideband signal from DC up to the maximum bandwidth. This is not the kind of RF signal being used in QC experiments, where BW is limited to a few tens or hundreds MHz. To generate such signals, Proteus uses much lower sampling rate IQ baseband waveforms to feed the internal numerical IQ modulator and finally converted to and analog signal. As the modulator is located close to the DAC, just the lower sampling rate IQ sample pairs must be transferred and those are defined with 16 bits as well as the calculations made by the DUC. So, for RF/uW modulated carriers, the sample resolution is 16-bit and the DAC is 14-bit. At the end what matters is the SFDR specification in the vicinity of the modulated carriers and Proteus can generate RF modulated signals with SFDR better than 80 dBs in most frequency bands.
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