Comtech EF Data CDM-570 - Manual (Page 47)

CDM-570/570L Satellite Modem with Optional IP Module Revision 12
Introduction MN/CDM570L.IOM
1–7
1.3.6 Hardware Options
There are three hardware options available: Reed-Solomon Codec, Turbo Product Codec, and the
IP Module Ethernet Interface. All three cards fit into expansion slots on the main circuit board.
1.3.7 Data Interfaces
The CDM-570/570L includes, as standard, a universal data interface that eliminates the need to
exchange interface cards for different applications. The interfaces offered include:
• EIA-422 (EIA530) DCE (at rates up to 9.98 Mbps)
• X.21 DTE and DCE (at rates up to 9.98 Mbps)
• V.35 DCE (at rates up to 9.98 Mbps)
• Synchronous EIA-232 DCE (at rates up to 300 kbps)
• G.703 E1 (2048 kbps), balanced and unbalanced (optional for units after 10/2009)
• G.703 T1 (1544 kbps), balanced
• Optional – integrated 10/100 BaseT Ethernet Interface.
1.3.8 Verification
The CDM-570/570L includes many test modes and loopbacks for rapid verification of the correct
function of the unit. The IF loopback, in particular, permits execution of a quick diagnostic test
without disturbing external cabling. During the loopback, all the receive configuration parameters
are temporarily changed to match the transmit side, and an internal RF switch connects the
modulator output to the demodulator input. When normal operation is again selected, all of the
previous values are restored.
1.3.9 AUPC
See Chapter 7. Automatic Uplink Power Control (AUPC) for detailed information
about this feature.
Automatic Uplink Power Control (AUPC) is an important feature that enables the
CDM-570/570L to automatically adjust its output power to maintain the E
b
/N
0
of the remote end
of the satellite link as constant. This provides protection against rain fading, a particularly severe
problem with Ku-band links.
To accomplish AUPC, the framed EDMAC mode of operation must be used. The distant end
modem constantly sends back information about the demodulator E
b
/N
0
using reserved bytes in
the overhead structure. The local modem uses the E
b
/N
0
to adjust its output power and create a
closed-loop feedback system over the satellite link.
A benefit of AUPC is that, whenever EDMAC/AUPC operation is selected, the remote
demodulator’s E
b
/N
0
can be viewed from the front panel display of the local modem. Note that
both EDMAC and AUPC can be used simultaneously.