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User Manual
Airbridge cBTS3612 CDMA Base Station
Normally Bi-polarization directional antenna is used in directional cell. Comparing
with the uni-polarization directional antenna, the bi-polarization directional antenna
is cost-effective, space saving and easy to install. However, uni-polarization omni
antenna is still adopted in omni cell.
4) Diversity technology
Electrical wave propagation in urban area has the following features:
Field intensity value changes slowly with places and times. It changes in the
l
rule of logarithmic normal distribution, which is called slow attenuation.
Field intensity transient value attenuates selectively since it is multi-path
l
transmission. The attenuation rules falls in Rayleigh distribution, which is called
fast attenuation.
Either fast attenuation or slow attenuation impairs the quality of communication or
even interrupts the conversation. Diversity technology is one of the most effective
technologies to tackle the attenuation problem. Diversity receiving and combining
technology can be used to minimize the attenuation when there is little correlation
between the two attenuated signals. There are polarized diversity and space
diversity. In the present mobile communication system, horizontal space diversity
and polarized diversity are both supported. Theoretical conclusion shows that space
diversity is effective when the distance between two antennae is over 10
wavelengths. Polarized diversity facilitates antenna installation and saves space,
therefore it is used more and more extensively.
5) Antenna isolation
The receiving/transmitting antenna must be installed with sufficient isolation to
minimize the effect on the receiver. The isolation space is subject to the out-band
noise of the transmitter and the sensitivity of the receiver. Please refer to cBTS3612
Installation Manual for details.
II. Feeder
Normally, the standard 7/8 inch or 5/4 inch feeders are used to connect the outdoor
antenna and indoor cabinet. In the site installation, 7/16 DIN connectors are needed
based on the actual length of feeders. Three grounding cable clips for lightning
protection should be applied at the tower top (or building roof), feeder middle, and
the wall hole where feeder enter indoors. If the feeder is excessively long, additional
cable clips are needed.
Since 7/8 inch feeder should not be bent, the tower top (or building roof) antenna
and the feeder, indoor cabinet and the feeder should be connected via jumpers. The
specifications of Huawei standard jumpers are 1/2 inch, 3.5m long, with 7/16DIN
connectors.
2-45
System Description
2 Hardware Architecture
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