Wegener UNITY4000, Instruction Manual

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2-1 UTY4000-003
SECTION 2
SYSTEM CONFIGURATION
2.1 UNIT OVERVIEW
The UNITY 4000 IRD features several separate hardware components: The DC switching
power supply, the main motherboard, an L-band DVB receiver, front-panel keypad controller
card, a front-panel LCD assembly, and the L-band RF switch. The DC switching power supply
provides all internal regulated DC power. The L-band RF switch is installed in the Module 2
expansion slot, and provides network or (if allowed by the network) local user selection of up to
four separate RF feeds. The selected RF feed output is connected to the DVB-compliant L-band
receiver card. This card tunes and demodulates the input QPSK carrier, and then applies two
layers of error correction decoding. Its output is the original (possibly encrypted) multiplex
MPEG transport stream which was input to the uplink IF modulator. This stream then feeds the
main motherboard, which decrypts (if necessary) the stream and then demultiplexes out the
selected video and audio elemental streams. These are, in turn, de-compressed and converted
back to the original analog source material for output. Meanwhile, the user may query the IRD
using the front-panel keypad for input and the LCD to read the returned status information.
2.2 BLOCK DIAGRAM DISCUSSION
Refer to Figure 2-1 (page 2-2) for the following discussion.
The DVB-compliant receiver card demodulates the incoming QPSK carrier. It implements both
FEC decoding and de-interleaving per the DVB standard. The decoded byte stream is output to
the main board.
The input to the main board is the multiplexed MPEG2 transport stream. If encryption is active,
then the decryption function is executed. The resulting “clear” transport stream is then made
available for output on the TRANSPORT OUT connector at the rear of the unit. In parallel, that
stream is fed to the transport demultiplexor, this device selects the component elemental stream
for selected video and audio programs, as well as the network control data streams. The selected
video data is passed to an MPEG video decoder which converts the signal to linear digital video.
This is then converted to analog NTSC in a final encoder for output. Meanwhile, the selected
MPEG compressed audio stream is also routed to a combined decompression and digital-to-
analog converter IC. The output is one stereo pair of audio signals (L and R) on Channel 1 at the
back panel. In addition to the first stereo pair, a digital signal processor monitors and
demultiplexes out another selected digital audio stream, which is also decoded and output as the
stereo pair on Channel 2 at the back panel.