Comtech EF Data SDM-300A - Manual (Page 29)

SDM-300A Satellite Modem Revision 6
Introduction MN/SDM300A.IOM
1–3
1.1 Overview
The SDM-300A Satellite Modem is a high performance, full-duplex, digital-vector,
modulator/demodulator that meets the open network requirements of the INTELSAT Earth
Station Standards (IESS) -308, -309, and -310 emulation specifications for the following:
• Intermediate Data Rate (IDR)
• INTELSAT Business Services (IBS)
• Satellite Multiservice System (SMS)
Additionally, the modem is used for many closed network satellite communication systems.
1.1.1 Modem Functions
Modulator Demodulator
Performs filtered BPSK, QPSK, Offset QPSK, and 8-PSK
modulation onto a variable frequency/amplitude carrier. Performs filtered BPSK, QPSK, Offset QPSK, and 8-PSK
demodulation from carriers of variable frequencies/amplitudes.
Encodes the data for the appropriate decoder. Decodes the data.
Scrambles the data. Descrambles the data.
Monitors and displays the modulator status without
interrupting service. Monitors and displays the demodulator status without interrupting
service
Performs self-test. Performs self-test.
Provide send clock timing.
1.1.2 Standard Features
• Differential encoder/decoder
• Built-in scramblers/descramblers
• TX and RX frequency synthesizers
• Multi-rate FEC convolutional Viterbi and Sequential Decoder
• Fully Accessible System Topology (FAST)
• Built-in self test
• Asymmetrical loop timing
• IDR Engineering Service Circuit (ESC) channel option of 64k data or two audio
channels
• Space Link Remote Control (SLRC)
• Selectable near or far end, baseband or interface loopback with any overhead option
enabled