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138 Chapter 5
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CDMA Measurements - Screens and Control Fields
CDMA Measurements
Error Vector Magnitude (EVM) Measurements
EVM
EVM is a measurement of the accuracy of the phase and amplitude of the
QPSK (Quadrature Phase Shift Keying) or Offset QPSK (OQPSK)
modulation. Expressed as a percentage, it is the RMS magnitude value
of the error vector which connects the ideal signal phasor to a measured
signal phasor at the detection decision points.
Figure 5-4 Components of Error Vector Magnitude
The magnitude of this error vector represents the “error” between the
ideal signal and the measured signal.
As part of the measurement, the signal is corrected for clock delay,
carrier frequency, carrier phase, and amplitude scaling.
Magnitude Error
Magnitude Error is the difference in the RMS magnitude value (in
percent) between the ideal signal phasor and the compensated,
measured signal phasor at the detected decision points.
Phase Error
Phase Error is the RMS value of the difference in phase (degrees)
between the ideal signal phasor and the compensated, measured signal
phasor at the detection decision points.
Screens on which this measurement is displayed
• CDMA ANALYZER
• CDMA GENERATOR
Ideal Signal
I
Measured Signal
Magnitude Error
Phase Error
Error Vector
Q
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