Mag Err (Digital Demod)

Mag Err is the RMS-average of the IQ magnitude error over all symbol times and expressed as a percentage of the EVM Normalization Reference. For all signals except FSK and CPM (FM), IQ magnitude errror is the difference in amplitude between the I/Q measured signal and the I/Q reference signal (for FSK or CPM (FM), see Mag Err: FSK).

The following graphic shows the calculation of IQ magnitude error for a single symbol (the normalization factor in this case is the EVM Normalization Reference).

$image\IQMagIQPhaseError_wmf.jpg$

Magnitude error is an indicator of the quality of the amplitude component of the modulated signal. For example, a very high magnitude error might indicate high incidental AM modulation on the signal.

The magnitude error shown in the symbol table is computed only from data at the symbol times (the instant in time when symbols are detected). The computation does not include points between symbols. Therefore, the value of Points / Symbol has no effect on this error data.

The symbol table also shows the symbol that has the largest magnitude error (peak magnitude error).

OQPSK/SOQPSK uses two points-per-symbol (symbols and midpoints between symbols) to compute magnitude error and the peak magnitude error due to the offset between I and Q.

For the EDGE demodulation format, the EVM, Phase, and Magnitude Error data results may vary for different points/symbol settings. When points/symbol is set to 1 (default), the trace data results are compensated for ISI (inter-symbol interference). For points/symbol greater than one, the trace data results are not compensated for the effects of ISI.