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Regarding DDC I/Q output spectrum for wideband RF sampling transceiver

Category: Software
Product Number: AD9988

Hello support team,

I am looking in to the wideband direct RF sampling transceivers. I have below query regrading AD9988 DDC output. 

My frequency is not fixed it is variable within +/- 1 MHz. So let's say, my center frequency = 40 MHz . so it will be vary within 39-41 MHz. 

So, If I choose NCO frequency = 39 MHz , then my DDC output spectrum would be from DC-2 MHz for input frequency of 39-41 MHz respectively. So, my DDC output will not be fixed , but will be variable within DC-2 MHz . and my total decimation would be reduced to 10 MSPS ( my final output rate) . Then as per nyquist theorem , my final sample rate is > 2* highest frequency component. 

so, the above is possible , right? to have DDC output(I,Q) vary within DC-2 MHz? based on my input frequency variation. as DC-2 MHz is within the range of decimating low pass filter. 

that means my DDC output will not be constant baseband I,Q but it will be variable baseband I,Q within the range of DC-2 MHz . This won't make any issue, right? As my input frequency is a single tone pure sine wave. it is not modulated signal. 

Kindly suggest weather my above understanding is correct or not?

Awaited your feedback and guidance as soon as possible.

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[edited by: Maitry at 5:44 AM (GMT -4) on 29 Jun 2022]