DVB QAM (Digital Demod)

Use the Format drop-down list to select a DVB QAM Quadrature Amplitude Modulation format that conforms to the DVB (Digital Video Broadcast (DVB) standard, EN 300 429. The VSA supports the following DVB QAM formats:

Format

DVB QAM signal format

DVB 16-QAM

16 QAM signals

DVM 32-QAM

32 QAM signals

DVB 64-QAM

64 QAM signals

DVB 128-QAM

128 QAM signals

DVB 256-QAM

256 QAM signals

The standard defines the bits that represent each state as follows:

I/Q Origin Offset Compensation

Unlike QAM, DVB QAM does not compensate for I/Q origin offset. When the demodulation format is DVB QAM, the VSA reports I/Q origin offset in the symbol table, but doesn't remove it from the measurement. When the demodulation format is QAM, the VSA reports I/Q origin offset in the symbol table AND removes it from the measurement.

To see the effects of I/Q origin offset on your DVB QAM signal, change the demodulation format to QAM. For example, if your signal is 16 DVB QAM, select 16-QAM to see the effects of I/Q origin offset removal on your signal.

The Error Vector Magnitude (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.) for DVB QAM will be higher than QAM because DVB QAM includes IQ origin offset in the measurement.

Reliable Carrier Lock

This table shows the minimum result length and frequency offset values for reliable carrier lock for DVB QAM signals:

Digital Modulation Format

Minimum Result Length (0 Hz frequency offset)

Maximum frequency offset (Result Length = 1000 symbols)

DVB 16-QAM

50 symbols

4.65% symbol rate

DVB 32-QAM

75 symbols

2.85% symbol rate

DVB 64-QAM

150 symbols

4.65% symbol rate

DVB 128-QAM

250 symbols

0.45% symbol rate

DVB 256-QAM

400 symbols

0.15% symbol rate

See Also

Available Digital Demodulation Formats (Digital Demod)