Table of Contents
Advertisement
CDM-710G High-Speed Satellite Modem
Introduction
Transmit (Tx) data is delivered to the data interface where it is converted to clock and data
signals for further processing. Depending upon the type of interface, clock and data are provided
or in other cases the clock is embedded in the data and clock recovery is performed to generate
clock and data signals.
A First-In–First-Out (FIFO) follows the terrestrial interface to facilitate delivery of the data to the
framing card. Data is passed to the Forward Error Correction (FEC) Encoder where the data is
framed and encoded in accordance with only DVB-S2 formats.
After encoding, the data is passed to the modulator where the I and Q signals are mapped to
generate the appropriate constellation (QPSK, 8PSK, 16APSK, and 32APSK) and filtered to
provide the desired spectral rolloff.
Finally, a carrier is generated by a frequency synthesizer in conjunction with the I and Q signals
to produce a frequency range, as follows:
CDM-710G (70/140 MHz)
CDM-710GL (L-Band)
An Rx carrier from the satellite is received by the demodulator and reverses the process
performed by the modulator. The demodulator has an FEC decoder that corrects errors incurred
during transmission to improve the integrity of the data delivered to the data interface. A
synthesizer in the demodulator is programmed to select the desired carrier from the transponder.
Physically, the CDM-710G is comprised of several main card assemblies:
•
The Data Interface card is a plug-in module that is readily installed or removed at the rear
of the unit.
Note: Power must be turned off to remove or install the data interfaces. Any attempt to
remove or install a data face without first turning off the power to the unit will result in
damage to the data interface.
•
The Framer Card receives signals from the data interface card and routes signals to the
FEC Encoder and Modulator. The microcontroller for the unit also resides on the Framer
Card and is the embedded controller for the entire unit. The microcontrollers handles all
of the monitor and control for unit including the front panel keypad and display, the RS-
232 and RS-485 2Wire / 4Wire remote port and the 10/100 Ethernet port. Interface with
the other the modules in the CDM-710G is provided by the framer assembly.
•
The FEC Encoder and Decoder cards are plug-in modules that reside on the Framer card.
They generate the encoded streams used by the modulator card.
•
Depending on the ordered configuration, a modulator and/or demodulator card may be
installed.
52 to 88 MHz and 104 to 176 MHz IF output signal at the
connector on the CDM-710G.
950 to 1950 MHz output signal at the Frequency connector on
the CDM-710GL.
1–4
Revision 1
MN-CDM710G
Advertisement
Table of Contents
