User Manual DDS200 Digital Demodulation System 070-9952-00

Manual OperationFigure 2–48: Constellation diagram of 64QAM signal with 20% amplitude imbalancePhase ErrorThe phase error (frequently also referred to as quadrature offset or quadratureerror) is the difference between the phase angles of the I and Q components,referenced to 90°. A phase error is caused by an error of the phase shifter ofthe I/Q modulator. The I and Q components are, in this case, not orthogonalto each other after demodulation. In the constellation diagram, a phase errorshows up by the signal states being arranged in a rhombus rather than asquare. See Figure 2–49.Figure 2–49: Constellation diagram of 64QAM signal with 8° phase error2–64 DDS200 Digital Demodulation System User Manual