Who's investigated using a DDS as a heterodyne/local oscillator signal source, replacing its crystal oscillator counterpart? I'm looking at an upper range of 45MHz. The AD9851 will generate a signal at that frequency but it begins to develop spurs above 20MHz. Is there a counterpart DDS which will develop a clean signal at 45MHz? Or another uncomplicated approach, such as running a lower-frequency DDS into a doubler then using a band pass filter on its output?