I am using AD9780 at 300MSPS, and output 100MHz and 7MHz sinusoidal waveform.
Are these waveforms normal?
Or are they too noisy?
The 7 Mhz scope picture looks about right. on the 100Mhz I get something a little different but also distorted. I think what you are seeing is the 100MHz with the image at 200MHz summed together, the image is only a few dB lower in amplitude. You have to is a low pass filter to remove the 200Mhz image and get a cleaner sine wave as you move up close to the 150MHz nyquist freq. As you approach the nyquist the image comes very close. If you tired say 120Mhz the image would be at 180Mhz and the combined waveform woudl look even worse.
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