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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
Maximum Composite
Operating Level
Absolute Maximum, No
Damage
FEC
Acquisition range
Acquisition time
Clock tracking range
Clocking modes
LNB 10 MHz Reference
LNB Voltage
Introduction
950-2250 MHz band:
-130 + 10
(symbol rate) to -80 + 10
log
50-180 MHz band:
-105 + 10
(symbol rate) to -70 + 10
log
950-2250 MHz band:
102 – 10
(symbol rate, desired carrier) dBC, +10 dBm max, with the additional requirement that
log
within ±10 MHz of the desired carrier, composite power is ≤ +30 dBC.
50-180 MHz band:
94 – 10
(symbol rate, desired carrier) dBC, +10 dBm max, with the additional requirement that
log
within ±10 MHz of the desired carrier, composite power is ≤ +30 dBc
+20 dBm
VersaFEC: 6 bit soft decision, proprietary
VersaFEC-2: 8 bit soft decision, proprietary
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
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
±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, 18VDC at 500 mA
maximum.
CDM-425 Advanced Satellite Modem
(symbol rate) dBm
log
(symbol rate) dBm
log
1–19
Revision 0
MN-CDM-425
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