Last Updated: August 29, 2007
This topic describes the Error Vector Magnitude measurement. Error Vector Magnitude is a measurement in the Dedicated Physical Channel measurement suite.
3GPP TS 34.121 section 5.13 states "The Error Vector Magnitude is a measure of the difference between the reference waveform and the measured waveform. This difference is called the error vector. Both waveforms pass through a matched Root Raised Cosine filter with bandwidth 3.84 MHz and roll-off alpha =0.22. Both waveforms are then further modified by selecting the frequency, absolute phase, absolute amplitude and chip clock timing so as to minimise the error vector. The EVM result is defined as the square root of the ratio of the mean error vector power to the mean reference power expressed as a %."
The EVM measurement in the test set compares the received signal's IQ modulation characteristics to an ideal signal, as defined in 3GPP TS 34.121 section 5.13 and annex B. As can be seen in the figure below, the error vector is the difference between the measured signal and reference signal.
Figure 1: Error Vector
Error Vector Magnitude is a measurement in the Dedicated Physical Channel measurement suite. See Dedicated Physical Channel Measurement Suite Measurement Parameters for details of the parameters that apply to measurements in the suite.
Error Vector Magnitude is a measurement in the Dedicated Physical Channel measurement suite. See Dedicated Physical Channel Measurement Suite Measurement Limits for details of the limits parameters that apply to measurements in the suite.
This result provides the integrity indicator for the Dedicated Physical Channel measurement suite. Normal indicates that the measurement suite completed successfully without error and the result is accurate. For details of other integrity indicators, see Measurement Integrity Indicator.
SCPI command: FETCh:WDPChannel:INTegrity?
The result indicates whether the Error Vector Magnitude measurement passes or fails.
SCPI command: FETCh:WDPChannel:EVM[:PARTial]?, FETCh:WDPChannel:EVM:ALL? (the pass/fail result is the second integer in the array returned for these commands)
This result provides the Error Vector Magnitude in % rms. If the Multi-Measurement Count is enabled, the average Error Vector Magnitude result is returned, otherwise the single measurement result is returned.
SCPI command: FETCh:WDPChannel:EVM[:PARTial]? (the EVM result is the third value in the array returned for this command), FETCh:WDPChannel:EVM:ALL? (the EVM result is the fifth value in the array returned for this command)
This result provides the maximum Error Vector Magnitude in % rms measured during a multi-measurement. This result is not displayed on the front panel when the Multi-Measurement Count is Off.
SCPI command: FETCh:WDPChannel:EVM:ALL? (the Maximum EVM result is the fourth value in the array returned for this command)
This result provides the minimum Error Vector Magnitude in % rms measured during a multi-measurement. This result is not displayed on the front panel when the Multi-Measurement Count is Off.
SCPI command:FETCh:WDPChannel:EVM:ALL? (the Minimum EVM result is the third value in the array returned for this command)
This result provides the standard deviation of the Error Vector Magnitude in % measured during a multi-measurement. This result is not displayed on the front panel when the Multi-Measurement Count is Off.
SCPI command: FETCh:WDPChannel:EVM:ALL? (the Standard Deviation is the sixth value in the array returned for this command)
This result provides the origin offset (distance away from the origin) in dB. Only averaged results are returned when the Multi-Measurement Count is enabled.
SCPI command: FETCh:WDPChannel:EVM:OOFFset[:AVERage]?
This result provides the phase error (degrees rms) with respect to the actual symbol location. Only averaged results are returned when the Multi-Measurement Count is enabled.
SCPI command: FETCh:WDPChannel:EVM:PERRor[:AVERage]?
This result provides the magnitude error (percent rms) with respect to the actual symbol location. Only averaged results are returned when the Multi-Measurement Count is enabled.
SCPI command: FETCh:WDPChannel:EVM:MERRor[:AVERage]?
Error Vector Magnitude is a measurement in the Dedicated Physical Channel measurement suite. See Dedicated Physical Channel Input Signal Requirements for details of the input signal requirements that apply to all measurements in the suite.
