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DTV Exciter with integrated 8-VSB
Modulator |
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Itelco
proudly present its DTV Exciter for high quality,
error free digital signal broadcasting fully
compliant with the ATSC (Advanced Television
Standards Commettee) 8-VSB (Vestigial Sideband)
DTV specifications (Document A/53).
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The exciter converts the
19.39Mbps serial data bit stream, carrying
video, audio, and data information, into a 1Watt
rms 8-VSB RF signal in either VHF or UHF.
Itelco� s know-how in RF systems and expertise
in digital signal processing ensure the optimal
integration of digital and analog
technologies. |
The exciter input is a 19.39Mbps
serial data stream (transport layer) which is
comprised of 188-byte MPEG-2 data packets. The
data packets are composed of one sync byte and
187bytes of data that provide a 19.39Mbps data
rate payload. The integrated modulator provides
frame synchronization, randomization of the input
data, forward error correction processing by means
of Reed-Solomon coding, Interleaving, Trellis
Coding which formats the data packets into data
frames for transmission, binary data segments sync
and data field sync insertion, modulation of a
single carrier with VSB shaping and Baseband to IF
conversion. The modulator output 8-VSB signal is
then upconverted to the VHF or UHF channel
frequency and amplified to the final RF
power.
VSB
Channel Occupancy |
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DTV EXCITER BLOCK DIAGRAM
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The
exciter has been designed with extensive use of
re-programmable devices making the equipment easy
to reconfigure. Adjustments due to modifications
of standard specifications or specific customer
requirements can be accomplished without replacing
any part. No custom parts are used but only
off-the-shelf components from leading companies in
the market. The Itelco ultra-reliable design
integrates advanced monitoring facilities
protecting the entire exciter against overloads
and failures. Due to the effective self diagnostic
capability each card is able to indicate its own
fault status. This results in great ease of
troubleshooting and minimizes the requirement for
the training of personnel, thus reducing repair
costs.The Itelco DTV Exciter is easy to operate.
LEDs on the front panel of the plug-in cards
provide an instant readout of the operating
status, e.g. fault conditions and corrections
bypass modes. The need for routine adjustments and
alignments is eliminated due to the digital
processing scheme. The exciter incorporates an
internal microprocessor-based control unit which
allows commands, configuration settings and major
parameter monitoring. |
VSB Data frame
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Settings are stored in a non-volatile
memory. The conveniently located remote control
interface provides both relay contact and a RS232
serial interface. The exciter features compact
dimensions. All plug-in cards, including the 8-VSB
modulator, are housed in a 19 inch 4HE chassis.
This chassis occupies the same rack space as a
traditional analog exciter, allowing easy upgrade
from NTSC or PAL to DTV service.ISO9001
certification assures the quality of Itelco
transmitters in every step from design to
production and customer
support. |
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TECHNICAL
CHARACTERISTICS |
Modulation |
8-level Vestigial Sideband Modulation
(8-VSB) |
Digital Mixing |
Digital I/Q modulation (preventing
phase and amplitude
unbalance) |
Modulator Input
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Parallel LVDS input and Asynchronous
serial Interface (ASI) (Optional). (both
conforming to DVB Doc.
A010) |
Input Data Rate |
19.39 Mbps |
Peak/Ave (99.9%) |
6.3 dB |
Channel Bandwidth |
6.0 MHz |
Excess Bandwidth |
11.5% |
Symbol Rate |
10.762
Msymbol/Sec. |
Bandwidth Efficiency |
11.5% |
Frequency Reference |
Interface for internal and external
GPS receiver (optional) |
Digital/Analog
Converter |
14-bit |
Modulator Output |
50 W
SMA, analog IF 43.8 MHz reserved spectrum
signal |
Inner Code Rates |
1/2; 2/3, 3/4, 5/6, 7/8 Punctured
convolutional |
IFFT Mode |
2k, 8k |
Guard Intervals |
1/4, 1/8, 1/16, 1/32 of symbol
duration |
Frequency Stability |
with GPS receiver: 5x10 E-11 / long
term; without GPS receiver: 1.5x10
E-7/year |
Frequency Step |
25 Hz |
Test Signals
(Facilities) |
Internal PRBS generator, ramp,
packetized ramp |
Monitoring Outputs |
Local Oscillator, IF output, RF
output |
Exciter Output |
50 W
N, 1 W(rms), on channel band III or bands
IV-V | | | |
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