Carrier-In-Carrier Summary; Glossary - Comtech EF Data DMD-2050E Installation And Operation Manual

DMD2050E Universal Satellite Modem

3.11.14 Carrier-in-Carrier Summary

Comtech EF Data's DoubleTalk Carrier-in-Carrier can provide significant savings in operational
expenses. The following should be considered when evaluating DoubleTalk Carrier-in-Carrier:
DoubleTalk Carrier-in-Carrier can only be used for full duplex links where the transmitting
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earth station is able to receive itself.
DoubleTalk Carrier-in-Carrier can be used in both bandwidth limited and power limited
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situations.
The maximum savings is generally achieved when the original link is symmetric in data rate.
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3.11.15 Glossary

Allocated Bandwidth
Bandwidth or Allocated Bandwidth or Occupied Bandwidth is the frequency space required by a
carrier on a transponder.
For example, a Duplex E1 (2.048 Mbps) Circuit with 8-PSK Modulation, FEC Rate 3/4 and 1.4
Spacing requires:
2.548 MHz = 2.048 / (3 * 0.75) * 1.4 * 2
For a 36 MHz transponder, 2.548 MHz corresponds to 7.078% Bandwidth Utilization.
Power Equivalent Bandwidth
Power Equivalent Bandwidth (PEB) is the transponder power used by a carrier, represented as
bandwidth equivalent.
PEB Calculation Example:
Transponder EIRP
•
Output Backoff (OBO)
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Available EIRP = 37 – 4
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Transponder Bandwidth
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Power Available / MHz
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If a carrier uses 24 dBW, its PEB
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This corresponds to 12.59% of available transponder power.
MN-DMD2050E Revision 2
= 37 dBW
= 4 dB
= 33 dBW = 10 = 1955.26 Watts
3.3
= 36 MHz
= 1955.26 / 36 = 54.424 W
= 10 / 54.424
2.4
= 4.532 MHz
Theory of Operation
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