I am new to DDS application and not sure if DDS is right way to achieve what we need.
My goal is to first provide a sweeping output from 13MHz to 14MHz at 1KHz step at the output of an interrogator.
The purpose is to find the exact resonant frequency of a RFID alike antenna within this band, and then
the interrogator would lock into this frequency to talk to this antenna ( and the device behand it). This is to be
done in a controlled environment, therefore FCC regulation is not a concern at this time.
I have an EVAL-AD9834SDZ evaluation board running in the lab and I am a bit surprised to see, on scope, ouput
waveforms near 13MHz all have noticable sawtooth on the trace (scope_1). After limiting scope probe bandwidth,
output traces look smoother by still have decernable ripples(scope_0). Please confirm these scope captures are
typical of DDS outputs.
With these ripples present (after low pass filter on the scope), my frequency counter reading varies +- 100KHz
when I set DDS output at fixed 11MHz ( for example). Does this tell me that I could not achieve a freq resolution
anything below 200KHz because of the ripple, dispite the fact that I have a 28 bit register on AD9834?
If AD9834 can not give me the control on resolution of 1KHz in eval board, could increasing the master clock freq help ?
Any solutions or other ICs you can suggest?
Thanks for your help,