I'm studying telecommunications, and would like to be sure to understand the maths behind these effects.

For IQ Imbalance and DC offset, it seems pretty clear why we observe a rectangle shape or a translation of the constellation, but for the quadrature skew, I don't see why we she this parallelogram shape, that stretch more when the skew is growing.

Could you please, neither with maths or graph explain this behavior ?

Thanks for your help !

Modulation problems graphs generated with LabVIEW

  • $\begingroup$ I think the name "phase imbalance" is more common than "quadrature skew" (unless I'm mistaking the effect). I recommend "Digital Signal Processing in Modern Communications Systems" by A. Schwarzinger, chapter 5. It is inexpensive and has the best review of impairments I've seen. $\endgroup$
    – MBaz
    Feb 27 '19 at 16:59
  • $\begingroup$ Yes, what I'm calling "Quadrature Skew" is the fact that the I and Q signal are not perfectly in quadrature (i.e phase difference of 90°), then Phase Imbalance seems to describe the same problem. I will check with this keyword if I can find more information on it. $\endgroup$
    – ISMAIL S.
    Feb 27 '19 at 18:54

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