Hi If you have a divide that's "inside" the range of the DAC, there are no nasty spurs (just DAC spurs). Once you are outside that range, there's a stepped triangle wave modulating the carrier. You get all the sidebands that you would expect from that very low frequency modulation. If the DAC is less than perfect it will toss in it's own "helpful stuff" as well.
It's not quite that simple of course. You have a dac width, a sine lookup table size / resolution and a phase accumulator width. You can also dither things. The stuff above will at least get you pointed in the right direction. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Hal Murray Sent: Thursday, October 25, 2012 12:45 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Adjusting HP 5065A frequency [email protected] said: > The gotcha with the DDS is phase truncation. That pretty much trashes the > ADEV. Thanks. How should I think about the output of a DDS? Lets assume I'm interested in the frequency domain where the "error" is measured in phase noise. For a DDS, I think they are spurs. Suppose I have a clock running at 101 MHz and I want 10 MHz. Is the output 10 MHz with some spurs, or 10.1 MHz with some spurs? Are there rules of thumb for the size and location of the spurs? (given the input freq and output freq) -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
