Vislink Strata RX, Technical Reference Manual

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Theory of Operation 9-13
Strata RX
Technical Reference Manual
9.6 Demodulation and Decoding
The Strata RX can provide either analog demodulation, using the
FM Receiver, or digital demodulation and decoding, using the
COFDM Demodulator and MPEG Decoder.
9.6.1 COFDM Demodulator
This module contains the Coded Orthogonal Frequency Division
Multiplexing (COFDM) demodulation circuitry.
The COFDM Demodulator automatically detects the key
modulation parameters of the incoming signal and configures
itself accordingly. These parameters include modulation type,
FEC, GI, Chroma, and Spectral Inversion. Only the COFDM
bandwidth (6, 7 or 8 MHz) and the receive channel/frequency
need to be specified by the operator.
In addition to demodulating the received COFDM (IF) signal, the
COFDM Demodulator microprocessor automatically locks to the
received digital signal and provides important signal
performance measurements such as
• RCL (Received Carrier Level)
• LQ (Link Quality)
• BER (Bit Error Ratio)
• SNR (Signal-to-Noise Ratio).
The signal performance measurements are made available to
the user on a real-time basis, either via the RCU and/or RXU
front panel displays, or by connecting a PC to the Strata RX RS-
232 serial port and running the Strata RX Configurator utility.
In addition, LQ and RCL are available through the Strata RX
Remote Control.
9.6.2 MPEG Decoder Circuit
The Strata RX MPEG decoder circuit accepts a digital ASI signal
from the COFDM demodulator and recovers the compressed
video (NTSC or PAL) and/or audio signals. Both analog and
digital (AES-EBU) audio signals are available at the RCU or RXU
Audio Output connector.
In addition, MPEG Decoder allows use of an external
synchronization signal (Gen Lock). The Gen Lock signal, at a
nominal 400 millivolts peak-to-peak, is connected to the MPEG
decoder via a rear panel BNC jack.
Additional features provided by the MPEG Decoder include a 9.6
kb/sec serial data wayside data channel and optional BISS
decryption capabilities.
9.7 Distribution, Command and
Control
The Distribution, Command and Control circuits are responsible
for external and internal communications as well as for
distributing the required DC supply voltages.
The RCU and RXU power supplies accept a wide range of DC
input voltages (+10.5 to +36 volts). The supplies convert the
input to the DC voltages required by the rest of the RX hardware.
The converted DC is controlled and distributed by the Control
and Distribution circuit.
The Command and Control circuits handle communications
between the RXU and RCU, and between the RX and external
control equipment such as a PC.
On-board microprocessors manage the overall system
configuration and operation of all modules to which they are
connected, i.e., MPEG/COFDM, FMR, RF/IF, etc.