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Interfacing AD9122 with AD5375 for DC offset null

Question asked by on Oct 5, 2011
Latest reply on Oct 12, 2011 by Tguy


I am working on nulling DC offset to get LO feedthrough rejection at output of modulator.

while reading datasheet of AD9122 DAC it was stated in that "Good sideband suppression requires both gain & phase matching of the I & Q signal."

My questions are below:

1) isn't the phase of I signal & Q signal are supposed to be offset by Pi/2?

2) If i want to use auxiliary DAC (register 0x42, 43, 46 & 47), what is the relation between the register values i can change in the DAC & what kind of rejection we get at output of modulator? will it be completely dependent on layout I have and leakage adds up dur to that?

3) if i want to use digital DC offset adjustments to null LO leakage, will it be a better choice if we use this instead of Aux Dac? do you have any comparison information to share?