Hi Brigid!
The question was originally posted by me.
A channel spacing of 2 KHz was used and Z-Com V674ME08 VCO was used.
The design issue has been resolved; the problem was with the prescaler value; i was using 8/9 instead of 4/5.
I use Windows 7, and the AD's Fractional N software wasn't showing an error on using the 8/9 prescaler below 3 GHz.
But, strangely enough, the LO was working previously when i used the 8/9 prescaler.
So, this question still remains un-answered as to how it was working by using a prescaler of 8/9 (provided all the other settings were same).
thanks for your support.
with best regards,
Humayun Zahid