Hi Lou,
Thanks for your response. I am generating the baseband pulse just as you are. Also, all pulses have the same transient behavior, not just the first one.
If it matters, I am using the CBX daughterboard and using a center frequency of 2 GHz. Unfortunately I do not have an oscilloscope that can display the frequencies that CBX transmits. So I run the signal into this NI equipment that downconverts the pulse to baseband and then records it. I use the same external clock to run both these equipments.
I realize that this set up makes it harder to debug the issue because I have another equipment involved. But I do not have another option as of now.
Thanks,
Lakshay.