Comtech EF Data CDM-500 - Manual (Page 63)

Spec Summary CDM-500 Closed Network Satellite Modem
A–2 Rev. 1.3
Output
impedance 50 and 75 ohms, front panel selectable
17 dB minimum return loss
Output
connector BNC female
Clocking options Internal, ±1ppm
External, locking over a ±100 ppm range
Loop timing (Rx satellite clock)
External TX
Carrier Off By TTL 'low' signal or external contact closure
hardware function automatically over-rides processor
A.2 Demodulator
(Data rate range, operating modes, de-scrambling, input impedance/return loss etc, as per Modulator specs)
Input power
range -30 to -60 dBm (desired carrier)
-8 dBm max composite
FEC Viterbi, 3 bit soft decision
Acquisition
range ±1 to ±32 kHz, programmable in 1kHz increments
Acquisition
time Highly dependent on data rate, FEC rate, and demodulator
acquisition range. Examples:
250 milliseconds average at 512 kbps, R1/2 QPSK, ±30kHz
acquisition sweep range, 6dB Eb/No
5 seconds average at 16 kbps, R1/2 QPSK, ±5kHz acquisition
range, 6dB Eb/No
21 seconds average at 8.2 kbps, R7/8 QPSK, ±2kHz acquisition
sweep range, 6dB Eb/No
Note that Rate 3/4 and Rate 7/8 FEC rates slow acquisition time
considerably, due to the additional time taken for the Viterbi
decoder to declare synchronization.
Clock tracking
range ± 100 ppm min
BER
Performance
(met in the
presence of
two adjacent
carriers, each
7 dB higher
than the
desired carrier) For:
BER=10
-5
BER=10
-6
BER=10
-7
Rate 1/2
Guaranteed
Eb/No:
(typical value
in parentheses)
5.4dB (4.9 dB)
6.0dB (5.5 dB)
6.7dB (6.2 dB)
Rate 3/4
Guaranteed
Eb/No:
(typical value
in parentheses)
6.8dB (6.3 dB)
7.4dB (6.9 dB)
8.2dB (7.7 dB)
Rate 7/8
Guaranteed
Eb/No:
(typical value
in parentheses)
7.7dB (7.2 dB)
8.4dB (7.9 dB)
9.0dB (8.6 dB)
Buffer Plesiochronous/Doppler buffer with selectable size of
512, 1024, 2048, 4096 or 8192 bits
Monitor
Functions Eb/No estimate
Corrected Bit Error Rate
Frequency offset
Buffer fill state