Comtech EF Data SDM-309B - Manual (Page 11)

Table of Contents SDM-309B Satellite Modem
viii Rev. 0
CHAPTER 5. THEORY OF OPERATION ...................................................................5–1
5.1 Modulator ......................................................................................................................................................... 5–1
5.1.1 General description..................................................................................................................................... 5–1
5.1.2 Specifications.............................................................................................................................................. 5–1
5.1.3 Theory of Operation ................................................................................................................................... 5–6
5.2 Viterbi Decoder / Demodulator Processor ..................................................................................................... 5–7
5.2.1 General Description .................................................................................................................................... 5–7
5.2.2 Viterbi Decoder/Demod Processor Specification ....................................................................................... 5–7
5.2.2.1 Demod Processor Specification........................................................................................................... 5–7
5.2.2.2 Viterbi Decoder Specifications............................................................................................................ 5–8
5.2.3 Theory Of Operation................................................................................................................................. 5–14
5.2.3.1 Demod Processor............................................................................................................................... 5–14
5.2.3.2 Viterbi Decoder ................................................................................................................................. 5–14
5.3 Demodulator ................................................................................................................................................... 5–15
5.3.1 General Description .................................................................................................................................. 5–15
5.3.2 Specifications............................................................................................................................................ 5–16
5.3.3 Theory of Operation ................................................................................................................................. 5–19
5.4 Reacquisition, Fast Acquisition And Directed Sweep ................................................................................. 5–19
5.4.1 General ..................................................................................................................................................... 5–19
5.4.2 Reacquisition ............................................................................................................................................ 5–20
5.4.3 Fast Acquisition ........................................................................................................................................ 5–21
5.4.4 Directed Sweep......................................................................................................................................... 5–21
CHAPTER 6. MAINTENANCE....................................................................................6–1
6.1 System Checkout .............................................................................................................................................. 6–1
6.1.1 General ....................................................................................................................................................... 6–1
6.1.2 Modulator Checkout ................................................................................................................................... 6–1
6.1.3 Demodulator Checkout ............................................................................................................................... 6–1
6.1.4 Test Points .................................................................................................................................................. 6–8
6.1.4.1 Modulator (Figure 6-5)........................................................................................................................ 6–8
6.1.4.2 Demodulator (Figure 6-6).................................................................................................................... 6–9
6.1.4.3 Viterbi Decoder/demod Card AS/0701 (Figure 6-7) ......................................................................... 6–10
6.1.4.4 Viterbi Decoder/Demod Card AS/0949 (Figure 6-8) ....................................................................... 6–11
6.1.4.5 Viterbi Decoder/Demod Card AS/2133 (Figure 6-9) ....................................................................... 6–12
6.2 Fault Isolation................................................................................................................................................. 6–13
6.2.1 Modulator Faults....................................................................................................................................... 6–13
6.2.2 Demodulator Faults .................................................................................................................................. 6–14
6.2.3 Common Equipment Faults ...................................................................................................................... 6–15
6.3 Interface Fault Isolation ................................................................................................................................ 6–15
6.3.1 Transmit Overhead Framing Unit Faults .................................................................................................. 6–16
6.3.2 Receive Overhead Framing Unit Faults.................................................................................................... 6–16
6.4 Module Replacement ..................................................................................................................................... 6–22
6.5 Module Identification .................................................................................................................................... 6–22