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Why can't we do quatrature upconversion in digital circuit?

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benchen

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I am confused by this. I found most of the diagram of transmitter does the quatrature upconversion in analog domain. And this will cause I Q mismatch. Why do't we do this in digital domain? for example, upconvert the IQ signal to a low IF and add them together in digital domain and then DAC and then use single LO to upconvert to fTX?
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RFDave

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Re: Why can't we do quatrature upconversion in digital circu

You can certainly do this, but it's not really practical.
To get a fully modulated signal, you need to have the DAC output at an IF frequency. Now you are faced with dealing with image rejection in your transmit chain, which makes the design more complicated. To increase the DAC output frequency high enough to make the image frequency easy to deal with will push the DAC clock rate high enough that the current is too much to deal with.

Dave
 

    benchen

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