We are using a AD9910 primarily to do sweeps from the high to low loit in DRG mode. We need to do multiple sweeps e.g. 250MHz to 150MHz then 150MHz to 75MHZ.
It is very important that between sweeps the DDS keeps the signal at the same frequency; in the above example the DDS must stay at 150MHz and move smoothly down to 75MHz. However we find that when the second sweep is initiated the signal snaps to the lower limit for at least 37ns.