DRAKE DQT1000 Kullanım Kılavuzu - Sayfa 5

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GENERAL DESCRIPTION

The R.L. Drake model DQT1000 is a professional quality,

digital headend transcoder that receives one or two ATSC,

or ATSC compatible MPEG2, 8VSB or QAM signals from

an off air antenna or from a CATV source. It demodulates

the signals to recover the MPEG2 transport stream(s),

multiplexes the MPEG2 transport streams from DEMOD A

and either the second RF input (DEMOD B) or the ASI

input if used, and modulates the resulting combined

stream using QAM modulation followed by a built in

upconverter for output to a CATV system.

The model MQM1000 does not contain a RF demodulator

but instead accepts one or two ATSC multiprogram

transport streams via two BNC, ASI inputs. When two

streams are input, the MQM1000 then multiplexes the two

ATSC streams in the same manner as the DQT1000.

The DQT1000 and MQM1000 provide essentially the

same function as the popular DQT860 and MQM860 units.

In addition, the '861' and '1000' models provide a program

filter function (a new Select Program menu) and offer

improved upconverter specs with phase noise reduced to

a level that is compatible with QAM modes up though

1024QAM.

The '1000' models provide the same features as the '861'

models except that the upconverter has been upgraded to

allow operation up to 1000 MHz on the output side. The

new '1000' models can be used with the Drake Digital

Headend Remote Control Software, version 2.6 or later,

for remote controlling or remote monitoring of operating

parameters. This program can also be used to download

new firmware into the unit if that ever becomes desirable.

The DQT1000 and MQM1000 operate in a fixed output

clock mode and process null packets when required to

maintain the set fixed clock rate. PCR correction is

included.

DIGITAL CHANNEL PROCESSING

The single input DQT1000, available by special order, is

ideal for digital 'channel processing' applications where a

single digital video signal is received, error corrected,

clocked at a user determined fixed rate and remodulated

on the same or another RF channel. Applications include

cleaning up a low MER QAM signal received from a CATV

source or fiber link receiver, or shifting the RF frequency of

a QAM modulated signal. It may be used to convert one

off-air ATSC 8VSB signal to a QAM output with rate

adjustment. Used in the processor mode with only one

input, the DQT1000 can process ATSC, DVB, or DigiCipher

II compliant MPEG2 inputs that are either VSB or QAM

modulated. No multiplexing or altering of any MPEG

tables is performed in this mode.

ENTER

ASI A

ASI B

26.88dB

24.52dB

General Description

MQM1000 Multiplexing QAM Modulator

Used in the non multiplexing mode, the data rate of the

incoming signal can be any rate that falls within the

specification range. The output rate can be set to any fixed

output rate (equal to or faster than the input rate).

MULTIPLEXING TWO ATSC TRANSPORT STREAMS

With the second RF input/tuner/demodulator (Demod B),

the DQT1000 can accept two 19.4 Mbps ATSC signals

(either with 8VSB modulation or QAM modulation) and

multiplex the transport streams to obtain a 38.8 Mbps

256QAM output. Thus two ATSC inputs can be output on a

single 6 MHz bandwidth 256 QAM channel.

Another way of combining two ATSC 19.4 Mbps streams is

to receive the first stream using the 8VSB input (Demod A)

and input the second stream, if available in ASI format, to

the optional ASI input on The DQT1000. Again the two

combined ATSC signals will be modulated at 256QAM in a

6 MHz wide channel.

If it is desired to provide both ATSC signals from ASI

sources, the model MQM1000 can be used.

When the DQT1000 or MQM1000 multiplexes two ATSC

inputs to produce a 38.8 Mbps output, no loss of picture or

sound packets occurs. There is no added compression

of the video or audio streams. Only the necessary control

packets are rewritten to prevent duplication of MPEG2

program numbers and major and minor channel number

assignments in the tables.

PROGRAM FILTERING

A 'Select Program' function is provided to allow the

operator to select which of the MPEG programs present

on the A and B input streams are to be included in the

output multiplex.

PSIP OPTIONS

When operating in the multiplex mode, the DQT1000 or

MQM1000 can be set to process PSIP information from

both sources and rewrite tables containing combined

PSIP information, or in cases where the off-air broadcast

channels may not be transmitting some or all of the

tables, it can be set to ignore and discard the PSIP tables

completely, or it can be set to generate MGT and VCT

tables without EIT tables. Null packet processing is

applied as necessary to keep the output data rate at the

desired setting. PCR correction is performed when

necessary.

OUTPUT

The RF output is always QAM regardless of whether the

input is VSB or QAM and the built-in agile upconverter

provides 61 dBmV output.