User's Manual
Bay Level Offset Calibration
May 2000
3-59
SC 4812T CDMA BTS Optimization/ATP
Introduction to Bay Level
Offset Calibration
Calibration compensates for normal equipment variations within the
BTS and assures maximum measurement accuracy.
RF Path Bay Level Offset
Calibration
Calibration identifies the accumulated gain in every transmit path
(BBX2 slot) at the BTS site and stores that value in a BLO database
calibration table in the LMF. The BLOs are subsequently downloaded to
each BBX2.
For starter frames, each receive path starts at a BTS RX antenna port and
terminates at a backplane BBX2 slot. Each transmit path starts at a
BBX2 backplane slot, travels through the LPA, and terminates at a BTS
TX antenna port.
For expansion frames each receive path starts at the BTS RX port of the
cell site starter frame, travels through the frame-to-frame expansion
cable, and terminates at a backplane BBX2 slot of the expansion frame.
The transmit path starts at a BBX2 backplane slot of the expansion
frame, travels though the LPA, and terminates at a BTS TX antenna port
of the same expansion frame.
Calibration identifies the accumulated gain in every transmit path
(BBX2 slot) at the BTS site and stores that value in a BLO database.
Each transmit path starts at a C–CCP shelf backplane BBX2 slot, travels
through the LPA, and ends at a BTS TX antenna port. When the TX path
calibration is performed, the RX path BLO is automatically set to the
default value.
At omni sites, BBX2 slots 1 and 13 (redundant) are tested. At sector
sites, BBX2 slots 1 through 12, and 13 (redundant) are tested. Only
those slots (sectors) actually equipped in the current CDF are tested,
regardless of physical BBX2 board installation in the slot.
When to Calibrate BLOs
Calibration of BLOs is required:
After initial BTS installation
Once each year
After replacing any of the following components or associated
interconnecting RF cabling:
– BBX2 board
– C–CCP shelf
– CIO card
– CIO to LPA backplane RF cable
– LPA backplane
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