2-6
Overview
Generating the RF Output
The RF modulator receives the OOB data transport multiplex created by the packet multiplexer
and performs the following functions to convert it for RF transmission:
Forward error correction
(FEC) encoding
An FEC encoder performs Reed/Solomon encoding, data interleaving, and data
randomization to reduce transmission errors.
QPSK modulation
A QPSK modulator converts the digital information in the OOB transport
multiplex into a synthesized analog waveform. The waveform is a 1.5 MHz-wide
signal with a carrier frequency centered at 44 MHz (IF).
Frequency upconversion
A frequency-agile converter processes the QPSK-modulated 44 MHz IF signal
to an RF output frequency configurable from 71 through 129 MHz.
Figure 2-4 shows a block diagram of the RF modulator:
Figure 2-4
RF modulator block diagram
From packet
multiplexer
RF
71-129 MHz
IF
44 MHz
To RF
distribution
system
To RF
converter
Frequency
converter
QPSK
modulator
FEC
encoder
Generating Serial Data Outputs
Depending on the routing, multiplexing, and PID re-assignment definitions contained in the
PID maps, the packet multiplexer directs input packets to serial data port destination queues
and multiplexes them into output datastreams in the same way it routes and multiplexes data
for the RF modulator.
Serial data ports must be configured as output ports to be valid output destinations.
OM 1000 Installation and Operation Manual
