Mid EVM (TD-SCDMA)

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

A perfect ideal midamble signal is synthesized at the chip level and identified as the reference midamble signal. The reference midamble signal is subtracted from the measured midamble 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 midamble signal is computed and expressed as a percentage EVM.

This parameter and the Comp EVM are 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.