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Airbridge cBTS3612 CDMA Base Station
Core
Lead in
DB25
Sheath
PGND
Figure 2-32 Principle of E1 lightning protection units
2.7.4 Lightning Protection for Antenna & Feeder Port
I. Lightning protection for RF antenna & feeder port
Antenna & feeder lightning protection is to protect against secondary lightning attack,
i.e. inductive lightning. Inductive lightning means that the feeder receives inductive
current at the moment of lightning attack, which may cause damage to the
equipment.
Inductive lightning can be prevented effectively in three ways:
The feeder is grounded at three points.
l
Antenna DC is grounded. The inductive current on the conductor of the feeder
l
can be discharged through the antenna.
CDU/DFU's DC is grounded. The inductive current on the conductor of the
l
feeder can be discharged through CDU/DFU.
When DDU is configured, lightning arrester should be used between the feeder
l
and indoor jumper.
With the above measures taken, up to 8kA lightning current can be endured.
II. Lighting protection for dual-satellite synchronization antenna & feeder
GPS/GLONASS antenna & feeder is protected with an additional lightning arrester
to prevent the damage caused by the lightning current induced on the core of the
antenna & feeder.
Lightning protection can be active or passive:
Passive lightning protection: The low frequency lightning current is grounded
l
based on microwave principle to provide protection.
2-62
System Description
2 Hardware Architecture
Lead out
DB37
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