Quad Err (Digital Demod)

Quad Err (Quadrature Skew Error) 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 I and Q are 87 degrees apart.

For non-rectangular formats (such as 8 PSK Phase Shift Keying: A broad classification of modulation techniques where the information to be transmitted is contained in the phase of the carrier wave. or pi/4 DQPSK Differential Quadrature Phase Shift Keying: QPSK modulation using differential encoding of the digital information stream.), IQ gain imbalance may show up as Quadrature Skew Error and vice-versa. This occurs when the VSA is phase locked to an orientation that is different than that of the modulator. To ensure the same phase orientation, use Sync Search. Use the digital demodulation Rotation parameter to swap the IQ Gain Imbalance and Quadrature Skew Error data results.

Quad Err is not available for FSK Frequency Shift Keying: A form of modulation using multiple carrier frequencies to carry the digital information. The most common is the two frequency FSK system using the two frequencies to carry the binary ones and zeros. or VSB Signals.