Table of Contents
Advertisement
CDM-600L Satellite Modem
Functional Description
Following this, the data passes to the Plesiochronous/Doppler buffer, which has a
programmable size, or alternatively bypasses the buffer. From here, the receive clock and
data signals are routed to the terrestrial interface, and are passed to the externally
connected DTE equipment.
Physically the CDM-600L modem is comprised of two main card assemblies.
•
•
These functions are shown in Figure 3-1.
TX G703 T1/E1
DEFRAMER AND
INTERFACE
TX AUDIO INTERFACE
RS-422, V.35 OR
RS-232
INTERFACE
LVDS
INTERFACE
G703 T2/E2
INTERFACE
OVERHEAD
INTERFACES
RX AUDIO INTERFACE
RX G703 T1/E1
DEFRAMER AND
INTERFACE
The first of these is the baseband framer card, which includes all of the interface
circuits, the framer/de-framer, plesiochronous/Doppler buffer, Reed Solomon
outer codec, and the main microcontroller.
The second card is the modem itself, that performs all of signal processing
functions of modulation, demodulation, and Forward Error Correction.
INT CLK
DDS
MUX
TX FRAMING
(IBS, IDR, D&I
OR EDMAC)
IBS OR
EDMAC
SCRAM-
BLER
TX LINE
DECODING
MICROPROCESSOR
& PROCESSOR FPGA
RX DE-FRAMING
RX LINE
(IBS, IDR, D&I OR
ENCODING
EDMAC)
BUFFER
IBS OR EDMAC
DESCRAMBLER
INSERT
DEMUX
INS CLK
BUFFER CLK
DDS
DDS
Figure 3-1. CDM-600L Modem Block Diagram
PL/9076
AS/0424
BASEBAND
MODEM
FRAMING
CARD
CARD
SEQ
ENCODER
TX REED-
SOLOMON
WITH
SCRAMB-
LER
ENC CLK
DDS
VITERBI
& TCM
CODEC
TURBO CODEC
W/ SCRAMBLER
& DESCRAMBLER
(OPTIONAL CARD)
INS CLK
DDS
DEC-
RX REED-
ODER
SOLOMON
WITH DE-
SCRAMB-
VIT/SEQ/OM73
LER
DESCRAMBLERS
DLF/NCO
3–2
MN/CDM600L.IOM
TXFIR
VIT/SEQ/OM73
SCRAMBLERS
I & Q FILTERS
TX IF
RX IF
FIR/PD & I/Q
RECOVERY
CARRIER
DACS
SEQ
SYM & BIT
TIMING
RECOVERY
BIT/SYM
DACS
Revision 2
Advertisement
Table of Contents
