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Complex Demodulator?

Question asked by Reson8r on Sep 1, 2011
Latest reply on Sep 7, 2011 by David.Buchanan

I have an application which requires direct complex downconversion of a modulated carrier which ranges from 10 kHz to 10 MHz.  The information BW is 20 kHz for all but the lowest carrier frequencies.  I need to downconvert this band to DC and extract phase information.  The signal is band limited to just over 10 MHz, regardless of the carrier frequency, and there may be out-of-band noise present.  I must avoid aliasing the noise into the baseband in the process of downconversion.  At baseband I will lowpass filter to remove out-of-band noise.  The phase of the signal relative to the demodulator reference is important to preserve, so I think this implies linear phase filtering, too.

 

I found the AD6620 which looks like it might work, but before I plow through the data sheet can anyone tell me if this is a good choice, or if there is a fatal flaw or a better choice?  Also, is it possible to phase lock the AD6620 internal NCO with an external DDS if the same reference clock is used for both?

 

Many thanks for any help!

Gerrit

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