Use the QAM (Quadrature Amplitude Modulation) modulation format to demodulate. The VSA supports , , , and modulation formats.
drop-down list to select aThis table shows the minimum
and frequency offset values for reliable carrier lock for QAM signals:
Digital Modulation Format |
Minimum Result Length (0 Hz frequency offset) |
Maximum frequency offset (Result Length = 1000 symbols) |
---|---|---|
16-QAM |
50 symbols |
4.8% symbol rate |
32-QAM |
75 symbols |
3.15% symbol rate |
64-QAM |
150 symbols |
4.65% symbol rate |
128-QAM |
250 symbols |
0.3% symbol rate |
256-QAM |
400 symbols |
0.3% symbol rate |
512-QAM |
1000 symbols |
0.15% symbol rate |
1024-QAM |
1000 symbols |
0.15% symbol rate |
2048-QAM |
4000 symbols |
0.1% symbol rate* |
4096-QAM |
4000 symbols |
0.1% symbol rate* |
*Using Low SNR Enhancement is required to make frequency locking robust for this QAM format.
QAM formats with 512 or more states are very sensitive to noise. Even an EVM of approximately 2% can cause symbol detection errors in the algorithm. This can cause a positive bias on EVM (an EVM appears better than it really would be for that signal). Analysis of these higher-order QAM formats is not intended with a Signal to Noise Ratio of less than 40dB.
See Also
Setting up a Digital Demod Measurement
Available Digital Demodulation Formats
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