Functional Description - Promax MO-160 Manual De Usuario

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High MER.
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Filter out up to 16 PID's.
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SPI,ASI or DVB-S IF input.
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Functional description

The MO-16X is a general purpose DVB-T modulator contained in a 19" 1U
chassis. The unit has three selectable MPEG-2 TS inputs (two serial ASI inputs and
one parallel SPI input or a demodulated DVB-S FI
used to modulate the COFDM signal in both non-hierarchical (one TS input) and
hierarchical (two TS inputs) modes. An additional test TS can be generated internally
in the modulator. This allows to generate compliant DVB-T signals even in the absence
of a valid TS input.
In slave mode, the useful bit rate at the TS input to the COFDM modulator has to
be the one defined in ETSI EN 300 744 for each choice of DVB-T transmission
parameters. The modulator automatically synchronises its internal clock to the incoming
TS packet rate. The slave mode allows to use one TS input with constant bit rate in
non-hierarchical modes. When using hierarchy, the user has to choose which TS (HP or
LP) the selected TS input is mapped to. This is the stream the modulator actually
synchronises to. The other hierarchical TS is generated internally as a PRBS test
sequence.
The input bit rate in slave mode should be within 0.1l of the values specified in
the DVB-T standard (See section "4.14 DVB-T useful bit rates") and approximately
constant. This operating mode is useful when re-modulating an off-air DVB-T signal
with the same parameters without the need to demultiplex and re-multiplex the transport
stream (as it would be the case in master mode).
The lock-in range of the MO-16X with respect to the TS rate is typically greater
than that of a COFDM demodulator. It's thus possible that the modulator is perfectly
synchronised in slave mode and, however, a DVB-T receiver is unable to acquire sync.
In master mode, the MO-16X is able to work with any incoming bit rate as long as
this is strictly lower than the value given in the DVB-T specification for the modulation
parameters in use (See section '4.14 DVB-T useful code rates'). The input TS bit rate is
adapted (bit rate adaptation) to the useful bit rate required by the DVB-T signal by
stuffing the TS with NULL packets (packet stuffing). This stuffing process alters the
sequence of PCR values embedded in the TS. These values have to be re-stamped for
the resultant PCR jitter to remain within the limits specified by the DVB. In hierarchical
modes, operating the MO-16X as master has the added advantage over the slave mode
of being able to use any of the three TS inputs as the HP input, LP input or both.
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Depending on the acquired model, it has a SPI or DVB-S IF, see the Table 1.
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USER'S MANUAL. MO-16X
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input). Either of these inputs can be
04/2008