Comtech EF Data DMDVR20 LBST Rev 1.1 - Manual (Page 25)

Theory of Operation DMDVR20 LBST Satellite Modem
3-4 TM136 – Rev. 1.1
Sync Data
I/O
Alarms
Form-C
Contacts
Fault
Form-C
Contacts
Open
Collector
Faults
Aux.
Interface(s)
Terrestrial
Interface
Rx DSP
Tx DSP
Digital
Baseband
Processor
Satellite
Modem
DEMOD
FPGA
MOD
FPGA
Modem
1 x 10 -7
Ref. 40
MHz Clk
LDPC
RCVR
Power
Supply
M&C
Front
Panel
Terminal
Remote
Port
10 Base-T
Ethernet
LAN Remote Serial Interfaces
100 – 240 VAC
50 – 60 Hz
-48 VDC
(Option)
IF Output
950-2050 MHz
0 to -25 dBm
Tx
RF
Equipment
Rx
RF
Equipment
IF Input
950-2150 MHz
Antenna
Figure 3-3. Satellite Modem Functional Block Diagram
3.1.1 Front Panel
The Front Panel includes a 2 x 16 backlit LCD Display, Indicator LEDs, and a Numeric Keypad
(refer to Section 4.1).
3.1.2 Baseband Processing
The Baseband Processor performs all Modulator functions required for an IBS Framing Unit, and
Reed-Solomon Codec. In addition, the Baseband Processing Section provides for transmit clock
selection and rate adaptation as well as a rate adapter and Plesiochronous/Doppler (PD) Buffer in
the receive direction. A multiplexer is also provided for the SCT Clock Source for Loop Timing
Applications. The transmit and receive paths are configured independently under processor
control.