IQ impairments are caused by the mismatch between the analog components of in-phase and quadrature paths in the RF chain. IQ impairments are characterized by three quantities, namely IQ gain imbalance, quadrature skew and timing skew.



  • IQ gain imbalance (dB) is the amount of amplifier and filter gain imbalance between I and Q signals. Quadrature skew (deg) is the deviation in angle from 90 degrees between the I and Q signals.
  • Timing skew (s) is the difference in sampling instances of I and Q signals.
  • Both timing skew and quadrature skew contribute to the phase mismatch between I and Q signals.

The following equation illustrates these quantities.



where

  • G = 10(IQ Gain Imbalance/20)
  • φ is the quadrature skew
  • τ is the timing skew
  • I'(t) is the impaired in-phase component of the signal
  • Q'(t) is the impaired quadrature-phase component of the signal
  • I(t) is the ideal in-phase component of the signal
  • Q(t) is the ideal quadrature-phase component of the signal