Comtech EF Data SDM-300L3 - Manual (Page 319)

SDM-300L3 Satellite Modem Revision 0
Specifications MN/SDM300L3.IOM
14–13
14.5.24 L-Band ODU Supply Voltage
Standard configuration is without a power supply for the external ODU or outdoor unit.
Two power options are available:
• 24V at 100W
• 48V at 150W
During power up of the modem, the ODU supply voltage initially powers up in the OFF
condition. During modem initialization, the ODU supply voltage is turned ON in a manner
that safely limits the current going to the ODU. The modem is protected for all short, open
and loaded conditions. The modem is programmable to turn the ODU supply voltage ON /
OFF.
14.5.25 ODU DC Current Sense
The indoor unit shall sense the magnitude of DC current delivered to the ODU and
provide programmable minimum and maximum current thresholds. An alarm is produced
when the sensed current to the ODU either falls below the minimum programmed
threshold or exceeds the maximum-programmed threshold. The value shall be for each
threshold is 0 to 4000 mA.
14.6 Encoding
14.6.1 BPSK Encoding
The modulator converts transmitted baseband data into a modulated BPSK carrier. Using
vector analysis of the constellation pattern, BPSK represents one symbol with the carrier
phase either at 0
° or 180 ° . The encoding characteristics for BPSK are provided in the
following table.
Code Rate Symbols/Bit Bps/Hz
1/1 1 2
1/2 2 0.5
5/16 3.2 0.3125
21/44 2.1 0.477
15.6.1 QPSK Encoding
The modulator converts transmitted baseband data into a modulated QPSK carrier at the
following parameters:
4.8 kbps to 2.5 Mbps (1/2 rate)
7.2 kbps to 3.75 Mbps (3/4 rate)
8.4 kbps to 4.375 Mbps (7/8 rate)