[time-nuts] DDS on AD9852

wb6bnq wb6bnq at cox.net
Sat Jan 17 02:33:49 EST 2015


I am not clear about the little sawtooth riding on the signal, but it 
looks like you are running out of headroom on the Ten-Tec preamp.  The 
Ten-Tec preamp would not be my first choice for the job.  One of the 
Minicircuits MMIC's would probably be a better choice depending upon 
your frequency range requirements.


d0ct0r wrote:

> Hello,
> I would like to ask some advise about the signal distortion I get from 
> my DDS project.
> The T-Bolt GPSDO is in use as a REF signal source (10Mhz) for AD9858 
> DDS. This chip has two COS analog outputs which opposite to each 
> other. I am using 20x reference multiplier in my project. And I am 
> using Low Pass filter and RF amplifier connected to ONE of the COS 
> output. The other output has no filter or op-amp on it. Attached is 
> four files with OSC screen shots, where the signal which goes through 
> the filter and amplifier somehow distorted. In contrary, the signal 
> from another output (without filter and op-amp) has near perfect 
> curve. I am using the same cable for connection to Oscilloscope.. And 
> I set 5 Mhz output on DDS as an example. In this my project I am using 
> Ten-Tec broadband pre-amp. The filter is standard Chebyshev Low Pass 
> filter made by MINI-CIRCUITS. Model PLP-90 (81 Mhz).
> Here is the link to Ten-Tec
> http://www.tentec.com/products/Universal-Low%252dNoise-Broadband-DC-to-1-GHz-RF-Preamp-%252d-Model-1001.html 
> Is it normal to have that kind of distortions for the signal, or 
> something wrong with design ?

More information about the time-nuts mailing list