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Demodulator Application Notes
01-0870-401B 01/03 83
Information Rates
The minimum and maximum information rates are provided in the following
table.
Output Spectrum Width
To prevent intersymbol interference, the outgoing symbols are filtered by a
DVB-compliant transmit filter. The filter type is a square-root raised cosine filter
with roll-off factor alpha = 0.35. The result is that the output spectrum has a width
of (1.35 * Symbol Rate).
The following table provides examples of information bit rates versus transponder
bandwidth at each code rate.
Estimating E
b
/N
0
The TRD6 provides an estimate of the E
b
/N
0
. To access this estimate:
■ Using the front panel, select Details>Input>Status>E
b
/N
0
■ Using a remote unit, issue the command DMD.x EBNO
E
b
/N
0
Definition
The E
b
/N
0
expression is defined as follows:
■ E
b
= Energy per information bit.
■ N
0
= Noise energy per Hz.
The formula for E
b
/N
0
, in dB is:
E
b
/N
0
= C(dBm) - N
0
(dBm/Hz) - 10log(IR)
where:
■ C = Carrier Power
■ IR = Information Rate
Minimum and Maximum Information Rates
Code Rate 1/2 2/3 3/4 5/6 7/8
Minimum Information Rate
(Mbps)
0.92 1.23 1.38 1.54 1.61
Maximum Information Rate
(Mbps)
27.6 36.8 41.5 46.1 48.4
Transponder
BW (MHz)
QPSK
1/2 Mbps
QPSK
2/3 Mbps
QPSK
3/4 Mbps
QPSK
5/6 Mbps
QPSK
7/8 Mbps
54 36.8627 49.1503 55.2941 61.4379 64.5098
46 31.4016 41.8668 47.1024 52.3360 54.9528
41 27.9884 37.3178 41.9826 46.6473 48.9797
36 24.5752 32.7669 36.8627 40.9586 43.0065
33 22.5272 30.0363 33.7908 37.5454 39.4227
30 20.4793 27.3057 30.7190 34.1322 35.8388
27 18.4314 24.5752 27.6471 30.7190 32.2549
18 12.2876 16.3834 18.4314 20.4793 21.5033