Comtech EF Data SLM-5650A Installation And Operation Manual page 489

G.5 DoubleTalk Carrier-in-Carrier Specifications
Operating Mode:
Requires the two links to share a common carrier frequency (Outbound and Inbound symbol rates
do not have to be equal)
Power Spectral Density Ratio and CnC Ratio:
•
BSPK/QPSK/8-PSK/8-QAM: –7 dB to +11 dB (ratio of power spectral density, outbound
interferer to desired inbound)
•
16-QAM: –7 dB to +7 dB (ratio of power spectral density, outbound interferer to desired
inbound)
With asymmetric carriers the absolute power ratio (or CnC ratio) would be
different, depending on the ratio of the symbol rates.
For Example:
•
•
•
•
Maximum Symbol Rate Ratio:
3:1 (TX:RX or RX:TX)
Inbound/Outbound frequency uncertainty:
Within the normal acquisition range of the demod, as follows:
•
Below 64 ksymbols/sec: ±1 to ±(Rs/2) kHz, where Rs = symbol rate in ksymbols/sec
•
Between 64 and 389 ksymbols/sec: ± 1up to a maximum of ± 32kHz
•
Above 389 ksymbols/sec: ±1 to ± (0.1Rs) kHz, up to a maximum of ± 200 kHz
Delay range:
0-330 ms
Eb/No Degradation (equal Inbound/Outbound power spectral density):
BPSK = 0.3dB
8-PSK = 0.5dB
For +10 dB power spectral density ratio (outbound interferer 10 dB higher than desired inbound)
add an additional 0.3 dB
Monitor Functions:
•
Delay, in milliseconds
•
Frequency offset (between outbound interferer and desired inbound). 100 Hz resolution
•
CnC ratio, in dB (ratio of absolute power, outbound interferer to desired inbound)
CnC Monitor Accuracy:
±1.0 dB for symmetric symbol rate
Appendix H
Outbound interferer = 1 Msymbols/sec
Desired Inbound = 500 ksymbols/sec
Ratio of power spectral density = +7 dB
Absolute power ratio (CnC Ratio) = +7dB + (10 log Outbound/desired
symbol rate) = +10 dB
QPSK = 0.3dB OQPSK = 0.3dB
8-QAM = 0.4dB 16-QAM = 0.6dB
G–23
SLM-5650A Satellite Modem
Revision 10
MN-SLM-5650A