Comtech EF Data CDM-625A - Manual (Page 60)

CDM-625A Advanced Satellite Modem MN-CDM625A
Introduction Revision 3
1–16
1.4.2 Demodulator
Note: Data rate range, operating modes, descrambling, input impedance/return loss etc, as per Sect. 1.4.1 Modulator.
Input power range, desired
carrier
950-2250 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
Maximum Composite Operating
Level
950-2250 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
Absolute Maximum, No Damage +20 dBm
FEC
Viterbi: 3 bit soft decision
Sequential: 2 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
VersaFEC: 6 bit soft decision, proprietary
VersaFEC-2: 8 bit soft decision, proprietary
Adaptive Equalizer 5-tap design, selectable on/off
Acquisition range Programmable in 1kHz increments, and subject to the following:
Below 64 ksymbols/sec: ±1 to ±(Rs/2) kHz, where Rs = symbol rate in ksymbols/sec
Between 64 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 ±300 kHz
Acquisition time 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.
Clock tracking range ±100 ppm min
Clocking modes Full range of clocking options supported – see plesiochronous/Doppler buffer section