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ADC32RF45: DDC does not output DC component

Part Number: ADC32RF45

Hi,

I am using ADC32RF45 at divide-by-4 mode. My CLK and NCO frequencies are 2949.12MHz and 1105.92MHz, respectively.
When I input a 1105.82MHz or 1106.02GHz CW signal, the ADC32RF45 outputs an IQ signal with the correct amplitude. However, when I input 1105.92MHz CW, which is the same frequency as NCO, the amplitude of the IQ signal becomes almost zero and the correct amplitude cannot be obtained. Ideally, the DDC should output an IQ signal with a DC component depending on the phase. The radius of the circle of the IQ signal trajectory must be constant regardless of the input signal frequency. The graph below shows the relationship between the radius (amplitude) of the IQ signal trajectory and the input CW signal frequency.

Does the ADC32RF45 have a high-pass filter or DC offset canceller that cuts the DC component at the DDC output? (I think the interleaver's DC offset canceller is located between the ADC cores and the DDC.) Is it possible to disable this feature?

Thanks,

Keiichi