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I/Q offset

Question asked by Daniel_Camara on Jun 2, 2015
Latest reply on Jun 12, 2015 by Daniel_Camara

Hi people,

 

This will probably seems stupid, for some one that has more experience on this than I do.... but I will ask any way.  I am trying to send a simple sinusoid in I and, the inverse of it in Q.  I manage to detect the signal... but it seems that the I and Q, they do not have the same reference (see image and look for the 0 on Y).  The noise part is pretty much OK, I mean the I and Q get varying around the zero, but when the signal starts I and Q vary, as expected, but clearly I is mostly above 0 and Q, well Q is more or less OK, but somewhat a little more below 0. What bothers me the most is that the received I/Q signals are somewhat shifted one from the other.

 

Is that expected? I mean, should I treat each one independently, that is, should I get the average from each one to use as a base line to decode the values of the signal? Or, even better, is there a configuration, or something like that (that I missed), and that can handle this offset between I and Q for me automatically?

signalI_Q.png

 

Best regards...

 

          Daniel

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