Comp Error Vector Time (TD-SCDMA)

When TD-SCDMA Demodulation is enabled, the Comp Error Vector Time trace data shows the time-domain error vector data results for the composite signal for the specified Analysis Timeslot and Analysis Sub-frame.

The Midamble field of the traffic timeslot is included in the data analysis. The shading in the trace display indicates the location of the midamble. The demodulation algorithm cannot deal with more than one midamble shift (k). If more than one midamble shift exists, measurement errors will occur.

For filter settling reasons, 4 chips at the start and end of the timeslot are ignored, resulting in data results that are 8 chips shorter than the full traffic timeslot length (not including the GP).

Measurement Concepts

Error Vector Time trace data is the computed error vector between corresponding chip points in the I/Q measured and I/Q reference signals. View the data results as Error Vector Magnitude, Error Vector Phase, only the I data results or only the Q data results (see Trace Data Formats below).

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Normalized data results

If normalization is OFF, the VSA shows the instantaneous magnitude for each point. If normalization is ON, the VSA shows the error vector as a percentage (see Normalize IQ Traces for an explanation of how this percentage is derived).

Trace Data Formats

It is important to remember that the Error Vector Time trace is a time record made up of complex, time-domain data. Each point in the time record has two components: I and Q. To make sense of the data, select an appropriate trace data format (Trace > Format > Format: drop- down list).

Linear Mag : Shows the EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. (Error Vector Magnitude).
Real(I) : Shows the I component of the error vector.
Imag(Q) : Shows the Q component of the error vector.
Wrap Phase: Shows the Error Vector Phase error.