Comtech EF Data SLM-7650 Installation And Operation Manual page 7

SLM-7650 Satellite Modem
Preface
CHAPTER 4. THEORY OF OPERATION ................................................................ 4-1
4.1 Overview......................................................................................................................................................4-1
4.2 Built in Test.................................................................................................................................................4-1
4.3 Definitions ...................................................................................................................................................4-3
4.3.1 Differential Encoding/Decoding ..............................................................................................................4-3
4.3.2 Scrambler/Descrambler............................................................................................................................4-3
4.3.2.1 Self-Synchronizing Scrambler/Descrambler...................................................................................... 4-3
4.3.2.2 Synchronous Scrambler/Descrambler ................................................................................................ 4-4
4.3.3 Encoding/Decoding..................................................................................................................................4-4
4.3.3.1 Convolutional/Viterbi (CEVD).......................................................................................................... 4-4
4.3.3.2 Reed-Solomon.................................................................................................................................... 4-5
4.3.3.3 Trellis Coding .................................................................................................................................... 4-6
4.3.3.4 Turbo Products Codec (Hardware Option) ........................................................................................ 4-7
4.3.3.5 Uncoded Operation (No FEC) ........................................................................................................... 4-9
4.3.4 Modulation Types ..................................................................................................................................4-10
4.3.4.1 BPSK ............................................................................................................................................... 4-10
4.3.4.2 QPSK ............................................................................................................................................... 4-10
4.3.4.3 Offset QPSK .................................................................................................................................... 4-10
4.3.4.4 8-PSK............................................................................................................................................... 4-10
4.3.4.5 16-QAM........................................................................................................................................... 4-11
4.3.5 Bit Error Rate .........................................................................................................................................4-11
4.3.6 Symbol Rate...........................................................................................................................................4-11
4.3.7 Symbol Rate Calculations ......................................................................................................................4-12
4.4 Theory of Operation.................................................................................................................................4-13
4.4.1 Modulator...............................................................................................................................................4-13
4.4.2 Demodulator...........................................................................................................................................4-14
4.4.3 Baseband Interface .................................................................................................................................4-17
4.4.3.1 Monitor and Control ........................................................................................................................ 4-17
4.4.3.2 Transmit and Receive Baseband ...................................................................................................... 4-17
4.4.3.3 Reference and Clock Distribution.................................................................................................... 4-24
CHAPTER 5. MAINTENANCE ................................................................................. 5-1
5.1 Modem Firmware Upgrade .......................................................................................................................5-1
5.2 Fault Isolation .............................................................................................................................................5-4
5.2.1 Fan............................................................................................................................................................5-4
5.2.2 M & C Battery..........................................................................................................................................5-4
5.2.3 Faults/Alarms ...........................................................................................................................................5-4
5.2.4 Fault/Alarm Display and Description.......................................................................................................5-8
5.2.5 Fault/Alarm Analysis ...............................................................................................................................5-9
5.2.5.1 Modulator Faults................................................................................................................................ 5-9
5.2.5.2 Demodulator Faults.......................................................................................................................... 5-10
5.2.5.3 Transmit Interface Faults ................................................................................................................. 5-10
5.2.5.4 Receive Interface Faults................................................................................................................... 5-12
5.2.5.5 Common Equipment Faults ............................................................................................................. 5-13
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MN/SLM7650.IOM