Popular Post mansr Posted December 23, 2019 Popular Post Share Posted December 23, 2019 42 minutes ago, Arpiben said: You are right and Mutec do provide measurements at output ports, quite rare to be mentioned. But one should keep in mind that the slaved oscillator inside DAC has its own noise characteristics...😉 Right, and due to the (lack of) relationship between the 10 MHz input and 24.576 or whatever DAC clock, some kind of frequency synthesis has to be used. The phase noise will most likely be dominated by this. pkane2001, marce and Arpiben 3 Link to comment
Popular Post mansr Posted December 23, 2019 Popular Post Share Posted December 23, 2019 7 hours ago, Arpiben said: @austinpop Please note that I am not arguing about Mutec good performances. But for several reasons, like the ones mentioned by @mansr, we should rather compare phase noise at DAC's output where it may matter. The advice is coming from somebody used to deal with phase noise and synchronization in Telecom industry. Feel free to delete. The easiest place to measure is probably at the clock input to the DAC chip. 7 hours ago, justubes said: But in any case take it that any improvement in the phase noise of an external reference will result in the same improvement at the dac. That's anything but certain. For a PLL based design, phase noise below the loop filter bandwidth is passed through while higher-frequency jitter it attenuated. Then the intrinsic phase noise of the VCO is added. At low frequency offsets, such as the 1 Hz discussed above, the greater of the the two phase noise sources will dominate. For a -110 to -116 dBc/Hz improvement in the reference clock to make a notable difference, the phase noise added by the clock synthesiser has to be around the same level or better. If it is that good, there is no reason to use the external reference in the first place, except to synchronise multiple devices. Arpiben, askat1988, marce and 1 other 4 Link to comment
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