When try to generate the waveform (40 MHZ --370 MHZ) from AD9914 Eval there is waveform distortion in all frequency range(40 MHz-- 370MHz) .Please see waveform attachment.
Per the AD9914 evaluation board schematic, the DDS output is ac-coupled to the SMA (J108) connector. Therefore, the iniial voltage will always start at 0v at the SMA node with no output frequency programmed. However, the reason for the positve jump in the waveform above is because the DDS output defaults to a cosine waveform instead of a sinewave waveform. So, to remove the initial positive step either enable the sine output bit in register 0x00 bit 16. Or you can use a phase offset value of 90 degrees. Try this and see if it helps.
What is the system clock of AD9914?
what do you mean by distorted?
What I can see is a staircase waveform output. It is to be expected for a DDS output because it is a sampled system. The staircase effect is dependent on the output frequency and the system clock of your DDS.
At the beginning of waveform there is glitch in the wave form. obtained while generating the digital ramp.
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