Demodulator - Comtech EF Data CDM-570 Installation And Operation Manual

CDM-570/570L Satellite Modem with Optional IP Module
Introduction
0.00 0.10 0.20 0.30
0
-5
Comtech EF Data
CDM-570L Transmit
-10
Power Spectral Density,
referred to symbol rate
-15
-20
-25
-30
-35
-40
-45
Spectral
-50
density,
dB
-55
1.4.2

Demodulator

Note: Data Rate Range, Operating modes, Descrambling, Input Impedance/Return Loss etc., are as
specified in Sect. 1.4.1 Modulator.
Input Power Range
FEC
Acquisition Range
Acquisition Time
Clock Tracking Range
0.40 0.50 0.60
Intelsat
IESS 308/309
limit
CDM-570 Desired Carrier: -30 to -60 dBm.
+35 dBc maximum composite, up to -5 dBm, absolute max.
CDM-570L Desired Carrier: -130 + 10 log (Symbol Rate) to -90 + 10 log (Symbol Rate).
+40 dBc maximum composite, up to –10 dBm, absolute max.
Viterbi: 3 bit soft decision
Trellis: Pragmatic TCM/8-PSK with closed network concatenated Reed-Solomon
Reed-Solomon (Closed Network): Proprietary
Turbo Product Codec: 4 bit soft decision, proprietary
±1 to ±32 kHz, programmable in 1 kHz increments, for symbol rates below 625 ksymbols/sec
±1 to ±200 kHz, 1 kHz increments, for symbol rates above 625 ksymbols/sec, CDM-570L only
Highly dependent on data rate, FEC rate, and demodulator acquisition range.
Examples: 120 ms average at 64 kbps, R1/2 QPSK, ±10 kHz acquisition sweep range, 6dB
3.5 s average at 9.6 kbps, R1/2 QPSK, ±10 kHz, 6dB Eb/No
Note: Reed-Solomon and TPC increases acquisition time, due to the additional time taken for the R-S/TPC
decoder to declare synchronization.
± 100 ppm min
0.70 0.80 0.90 1.00
CDM-570L Modulator
typically < -50 dB, and
guaranteed to be
< -45 dB at offsets
> 0.75 Rs
1–13
Revision 12
MN/CDM570L.IOM
1.10 1.20 1.30 1.40
Symbol Rate, Rs
Intelsat
IESS 308/309
limit
E /N
b 0
1.50