Demodulator - Comtech EF Data CDM-625 Installation And Operation Manual

CDM-625 Advanced Satellite Modem
Introduction
1.7.2

Demodulator

Data rate range, operating modes, de-scrambling, input impedance/return loss etc, as per Modulator.
Input power range,
desired carrier
Maximum Composite
Operating Level
Absolute Maximum,
No Damage
FEC
Adaptive Equalizer
Acquisition range
Acquisition time
Clock tracking range
Clocking modes
LNB 10 MHz Reference
LNB Voltage
LNB Current Alarm
VITERBI
BER performance
(met in the presence of
two adjacent carriers,
each 7 dB higher than
the desired carrier)
VITERBI and RS 220,200
or 200,180 Outer Code
BER
(with two adjacent
carriers, each 7 dB
higher than the desired
carrier)
950-1950 MHz band:
-130 + 10 log(symbol rate) to -80 + 10 log(symbol rate) dBm
50-180 MHz band:
-105 + 10 log(symbol rate) to -70 + 10 log(symbol rate) dBm
950-1950 MHz band:
102 – 10 log(symbol rate, desired carrier) dBC, +10 dBm max, with the additional requirement that
within ±10 MHz of the desired carrier, composite power is ≤ +30 dBC.
50-180 MHz band:
94 – 10 log(symbol rate, desired carrier) dBC, +10 dBm max, with the additional requirement that
within ± 10 MHz of the desired carrier, composite power is ≤ +30 dBC
+20 dBm
Viterbi: 3 bit soft decision
Trellis: Per IESS-310
Reed-Solomon(Open Network): Per IESS-308/309/310
Reed-Solomon(Closed Network): Proprietary
Turbo Product Codec: 6 bit soft decision, proprietary
LDPC: 5 bit soft decision, proprietary
5-tap design, selectable on/off
Programmable in 1kHz increments, and subject to the following:
Below 32 ksymbols/sec: ±1 to ± (Rs) kHz, where Rs = symbol rate in ksymbols/sec
Between 32 and 389 ksymbols/sec: ± 1 up to a maximum of ± 32kHz
Above 389 ksymbols/sec: ±1 to ± (0.1Rs) kHz, up to a maximum of ± 200 kHz
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 Eb/No
2 s average at 18 kbps, R1/2 QPSK, ±10 kHz, 6dB Eb/No
Note: The use of Reed-Solomon, TPC, LDPC, VersaFEC increases acquisition time, due to the
additional time taken for these decoders to declare synchronization.
± 100 ppm min
Full range of clocking options supported – see plesiochronous/Doppler buffer section
On center conductor of L-Band input connector, selectable ON/OFF. Level: -3dBm ± 3 dB.
Source: either Internal modem reference or External reference
Performance: For phase noise, refer to L-Band modulator 10 MHz. Frequency stability same as the
modulator 10 MHz reference.
On center conductor of L-Band input connector, selectable ON/OFF, 13, 18 volts per DiSEq 4.2 and
24VDC at 500 mA maximum.
Programmable MIN and MAX current alarms.
Rate 1/2 (B, Q, OQ)
Guaranteed Eb/No:
(typical value in
parentheses)
For:
-5
BER=10 5.4 dB (4.9 dB)
-6
BER=10 6.0 dB (5.5 dB)
-7
BER=10 6.7 dB (6.2 dB)
Rate 1/2 (B, Q, OQ)
Guaranteed Eb/No:
(typical value in
parentheses)
For:
-5
BER=10 4.3 dB (4.0 dB)
-6
BER=10 4.4 dB (4.1 dB)
-7
BER=10 4.5 dB (4.2 dB)
MN-0000036 (Ref MN/CDM625.IOM)
Rate 3/4 (Q, OQ)
Guaranteed Eb/No:
(typical value in
parentheses)
6.8 dB (6.3 dB)
7.4 dB (6.9 dB)
8.2 dB (7.7 dB)
Rate 3/4 (Q, OQ)
Guaranteed Eb/No:
(typical value in
parentheses)
5.6 dB (4.7 dB)
5.8 dB (4.8 dB)
6.0 dB (5.2 dB)
1–12
Revision 1
Rate 7/8 (Q, OQ)
Guaranteed Eb/No:
(typical value in
parentheses)
7.7 dB (7.2 dB)
8.4 dB (7.9 dB)
9.0 dB (8.6 dB)
Rate 7/8 (Q, OQ)
Guaranteed Eb/No:
(typical value in
parentheses)
6.5 dB (6.0 dB)
6.7 dB (6.2 dB)
6.9 dB (6.5 dB)