Comtech EF Data CDM-550T, Руководство пользователя

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Summary Of Specifications CDM-550T Satellite Modem
14–2 Rev. 1.3
FEC
None : Uncoded BPSK/QPSK/OQPSK
Viterbi: k=7, per IESS 308/309
BPSK: Rate 1/2
QPSK/OQPSK: Rate 1/2, Rate 3/4 and Rate 7/8
Sequential:
k=36 (Rate 1/2) per IESS 309
k= 63 (Rate 3/4) per IESS 309
k= 87 (Rate 7/8)
Reed-Solomon (Optional plug-in card):
220,200 outer code (transparent modes)
200,180 outer code (EDMAC modes)
Interleaver depth = 4 (Viterbi)
Interleaver depth = 8 (Sequential)
Turbo Product Codec (Optional plug-in card):
Rate 3/4 QPSK/OQPSK - 2 dimensional
Rate 21/44 BPSK - 3 dimensional
Rate 5/16 BPSK - 3 dimensional
Output frequency 52 - 88 MHz, 100 Hz resolution
(140 MHz band optional, 104 - 176 MHz)
Stability ±1.5 ppm, 0 to 50
o
C
Harmonics and
spurious Better than -55 dBC/4 kHz (typically <-60 dBC/4kHz)
Transmit on/off
ratio
55 dB minimum
Output phase noise < 0.24
0
rms double sided, 100 Hz to 1MHz
(minimum of 22 dB better overall than the INTELSAT
IESS 308/309 requirement)
Output power 0 to -20 dBm, 0.1 dB steps - manual mode. See Automatic Uplink Power Control section also.
Accuracy ±0.5 dB over frequency and temperature
Output impedance
50 and 75 ohms, front panel selectable
17 dB minimum return loss
O/P connector BNC female
Clocking options Internal, ±1ppm
External, locking over a ±100 ppm range
Loop timing (Rx satellite clock) - supports asymmetric operation - Rx and Tx data rates do not need to be
identical
External TX
Carrier Off
By TTL 'low' signal or external contact closure - hardware function automatically over-rides processor
14.2 Demodulator
Data rate range, operating modes, de-scrambling, input impedance/return loss etc, as per Modulator
Input power range
-30 to -60 dBm (desired carrier)
+35 dBC maximum composite, up to -5 dBm
FEC Viterbi: 3 bit soft decision
Sequential: 2 bit soft decision
Turbo Product Codec: 6 bit soft decision
Acquisition range ±1 to ±30 kHz, programmable in 1kHz increments
Acquisition time Highly dependent on data rate, FEC rate, and demodulator acquisition range. Examples: 250 ms average
at 512 kbps, R1/2 QPSK, ±30kHz acquisition sweep range, 6dB Eb/No
5 s average at 16 kbps, R1/2 QPSK, ±5kHz, 6dB Eb/No
21 s average at 8.2 kbps, R7/8 QPSK, ±2kHz, 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 FEC decoder to declare synchronization.