User's Manual Part 2

Bay Level Offset Calibration

DRAFT

SCt4812T CDMA BTS Optimization/ATP

Mar 2001

3-64

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 (BBX

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 BBX.

For starter frames, each receive path starts at a BTS RX antenna port and

terminates at a backplane BBX slot. Each transmit path starts at a BBX

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 BBX slot of the expansion frame.

The transmit path starts at a BBX 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 (BBX

slot) at the BTS site and stores that value in a BLO database. Each

transmit path starts at a C–CCP shelf backplane BBX 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, BBX slots 1 and 13 (redundant) are tested. At sector sites,

BBX slots 1 through 12, and 13 (redundant) are tested. Only those slots

(sectors) actually equipped in the current CDF are tested, regardless of

physical BBX 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:

– BBX board

– C–CCP shelf

– CIO card

– CIO to LPA backplane RF cable

– LPA backplane

– LPA

. . . continued on next page