Doubletalk Carrier-In-Carrier Specifications - Comtech EF Data DMD-2050E Installation And Operation Manual

DMD2050E Universal Satellite Modem

3.11.13 DoubleTalk Carrier-in-Carrier Specifications

Operating Mode
Power Spectral Density Ratio and
CnC Ratio
Maximum Symbol Rate Ratio
Inbound/Outbound frequency
uncertainty
Delay range
Eb/No Degradation
(equal Inbound/Outbound power
spectral density)
Monitor Functions
MN-DMD2050E Revision 2
Requires the two links to share a common carrier frequency (Outbound and
Inbound symbol rates do not have to be equal)
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)
Note: With asymmetric carriers the absolute power ratio (or CnC ratio) would
be different, depending on the ratio of the symbol rates.
Example:
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
3:1 (TX:RX or RX:TX)
Within the normal acquisition range of the demod, as follows:
Below 32 ksymbols/sec: ±1 to ± (Rs/2) kHz, where Rs = symbol rate in
ksymbols/sec
Between 32 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
0-330 ms
BPSK = 0.3dB QPSK = 0.3dB
8-PSK = 0.5dB 8-QAM = 0.4dB 16-QAM = 0.6dB
For +10 dB power spectral density ratio (outbound interferer 10 dB higher than
desired inbound) add an additional 0.3 dB
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)
Theory of Operation
OQPSK = 0.3dB
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