AnsweredAssumed Answered

AD9913 output reconstruction

Question asked by fgi on Aug 18, 2017
Latest reply on Aug 24, 2017 by mcee

Dear all, 

 

 

 

I'm trying to interface a AD9913 DDS to a bandpass filter. The idea is that the AD9913 generates a sweep from 48 to 53 MHz (done!).  I use the bandpass filter to reconstruct the DDS output and the output of the bandpass filter is fed into an amplifier to amplify the filter output to a combined differential output of 2Vpp. (so, 1Vpp per one side of the differential pair).

 

Currently i'm not that satisfied with the filter output swing.  I already tried to boost the input swing at the input of the filter to ±400mV (max AC compliance voltage of DDS) by increasing the termination resistors from 50 to 200 ohms. And to match the filter input impedance; I designed a new filter with a input impedance of 200 ohms. 

 

I already read the following documents; 

 

Interesting topology(?); 

http://www.analog.com/media/en/reference-design-documentation/reference-designs/CN0304.pdf 

 

interfacing a DDS;

http://www.analog.com/media/en/training-seminars/design-handbooks/Technical-Tutorial-DDS/Section6.pdf 

 

I attached the circuit I started with, my question is;  is this the way to go to create a clean 48 to 53 MHz sweep with a voltage swing of at least 2Vpp?

 

Thanks in advance. 

Outcomes