Comtech EF Data CDD-880, Installation And Operation Manual

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CDD-880 Multi Receiver Router MN-CDD880
Appendix G Revision 2
G–5
G.2.2.2.1 Power Reference
Reference Calibration uses the listed operational essentials to take a unique approach in
determining a power reference. This approach allows setting the reference at any point during
dSCPC operation. However, to avoid the risk of improper entrance link balance, the operator
MUST calibrate at the time of antenna commissioning.
The DPC Power Scale ( Figure G-1 ) represents the different calibration levels and limits
depending on link-budgeted power parameters. When using the DPC Reference Calibration, the
requirements that follow must be taken into consideration to determine link quality and the
achievable maximum power.
G.2.2.2.2 Reference Calibration
Per Figure G-1: Line 1 (the green line) represents the calibration point which you may call any
time during dSCPC operation. Reference calibration uses current symbol rate and MODCOD to
target error-free link quality. Reference recalibration, during normal operation, forces re-
evaluation, which could represent a different point on the scale, but not modifying maximum
power set points.
G.2.2.2.3 Rated Maximum Power
Per Figure G-1: Line 2 (the blue line) indicates the breakpoint of rated maximum power given by
the link budget parameters of maximum data rate, MODCOD, and margin. This is the power
adjustment between clear-sky and fade conditions and how much additional power is applied
without exceeding assigned terminal PEB.
This assumes hub downlink fade or backoff condition
is not set/unknown.
G.2.2.2.4 Terminal Maximum Power
Per Figure G-1: Line 3 (the red line) shows terminal maximum power if the hub downlink fade
condition is given and the remote’s BUC gain compression point is known.
Without these two variables, the terminal is not allowed to increase power beyond the rated
maximum; with these two pieces of information, the hub backoff control allows the power to
adjust greater than budgeted margin.
G.2.2.2.5 Target Power
The target power for DPC is based on MODCOD switch-points ( Figure G-2 ), which correspond to
SNR requirement for BER = 5 x 10
-8
.
The calculated target power for a given E
S
/N
0
is increased by one switch-point in this table; this
is done to prevent unnecessary ACM switching if the terminal power is marginal, and also to
give full range for set MODCOD. This targeted power increase is independent of ACM operation.