TANDBERG SM6630 User Manual - page 7
SM6630 and SM6635 Satellite Modulators
7
1.4.6 DVB-S2
and
PREKOR
Capability
1
Modulator models SM6630 and SM6635 are both DVB-S2 capable and incorporate
TANDBERG Television’s proprietary PREKOR Dynamic Pre-correction system.
The PREKOR system corrects non-linear magnitude and phase distortions, and
group delay distortion introduced by the uplink HPA and satellite transponder. It is
of particular benefit when using higher order modulations such as 16QAM,
16APSK or 32APSK.
1.4.7
Forward Error Correction Coding
Noise and interference can cause some bits to be received in error. Therefore,
Forward Error Correction (FEC) is used to add redundancy, i.e. extra bits, to the
transmitted signal. This allows a large number of errors at the receiver to be
corrected by the FEC decoder. The FEC coding scheme used depends on the
modulation standard selected. The DVB-S and DVB-DSNG standards employ a
concatenated coding scheme consisting of an outer Reed-Solomon (RS) code, bit
interleaving and an inner convolutional code. The DVB-S2 standard employs a
concatenated coding scheme consisting of an outer Bose-Chaudhuri-
Hocquenghem (BCH) code and an inner Low Density Parity Check (LDPC) code.
Each FEC coding scheme provides for a number of different code rates, permitting
a trade-off between bit-rate and ruggedness.
1.4.8 Modulation
Schemes
DVB-S BPSK and QPSK modulations are available as standard on each base unit
model. Additionally, DVB-DSNG 8PSK and 16QAM modulations are available with
the SM66XX/SWO/HOM option. DVB-S2 QPSK, 8PSK, 16APSK and 32APSK
modulations are available as options.
1.4.9 Symbol
Rate
Range
Each base unit model has a symbol rate range of 0.1 to 5 Msymbol/s as standard.
Extended symbol rate ranges of 0.1 to 48 Msymbol/s and 0.1 to 66 Msymbol/s are
available with the SM66XX/SWO/48MSYM and SM66XX/SWO/66MSYM options,
respectively.
1.4.10 IF
Tilt
Correction
Both base unit models incorporate a digital IF tilt corrector having a linear
amplitude versus frequency response with user-controllable slope. This facility is
intended for correcting the frequency dependent attenuation that may be
introduced by long IF output cables.
1
The appropriate software options are required to enable the DVB-S2 and PREKOR functionality.
See Table 1.2: Software Options.