EVM (TD-SCDMA)

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. is the Composite Error Vector Magnitude for the composite signal. The display shows these EVM values: the RMS (root mean square) EVM, the Peak (largest) EVM and the chip number with the Peak EVM.

A perfect ideal signal is synthesized at the chip level and identified as the reference signal. The reference signal is subtracted from the measured signal to produce a time record of error phasors. The square root of the ratio of the mean power of the error signal to the mean power of the reference signal is computed and expressed as a percentage EVM.

This parameter is similar to digital demodulation EVM except that it is computed at the chip rate instead of the symbol rate. See Digital Demodulation Error-Vector Magnitude (EVM) for further information about this parameter.