We are using AD9857 in our DVB-T modulator board. Now it could work, but the output of AD9857 is too low. It is -76dbm. (Measured using a Spectrum Analyzer. ). Could you help me? Thanks. The schematic is attached.
If you're in modulation mode, you must drive the IQ data lines, else the data lines are pulled low via internal pulls down resistors. That would greatly reduce the amplitude of the output carrier signal per your description. Have you tried single tone mode. In that mode, do you have a strong output carrieer signal?
Note, in single tone mode, the output scalar multiplier defaults to 1.414x and that will cause carrier distortion (clipping at the DAC input), so set the valut to 1.0x in single tone mode.
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