IQQuadErr (802.11n/ac/ax/be)
(IQ Quadrature Error), also called Quadrature Skew, indicates the orthogonal error between the I and Q signals. Ideally, I and Q should be orthogonal (90 degrees apart). A quadrature skew error of 3 degrees means that I and Q are 93 degrees apart. A positive quadrature skew error corresponds to moving the Q axis counter-clockwise with respect to the I axis, resulting in an angle larger than 90 degrees in the upper right quadrant.
Quadrature Error for OFDM demodulation differs from Quadrature Error for single carrier modulation in that quadrature error does not show up in the constellation diagram as an angled constellation. This is because OFDM constellations are in the frequency domain instead of in the time domain. In an OFDM signal, quadrature skew error causes each subcarrier to interfere with its opposing subcarrier which results in spreading each constellation point into a miniature picture of the entire constellation.
In MIMO systems, Quadrature Error can also cause interference between the data streams of multi-data-stream signals.
See Also
