3. When installing the service antenna in a relatively high location, lightning
arrestors are necessary. Grounding of arrestor and antenna is essential.
4.
Waterproofing of service antenna’s connector with sealant is highly
recommended.
3.2.3 Isolation
Isolation is an important concept when it comes to the implementation of a
booster system, especially for the outdoor project. There must be sufficient
isolation within the booster system, which means there must be enough distance
and obstacles between the donor and the service antennas, and their directions
are recommended to be in opposite directions. The propagation loss between
the antennas needs to be at least 15dB above the gain value used by the
booster. Non-compliance to this criterion can result in poor signal to the
coverage area and may damage the PA of the booster.
3.2.3.1 Self-oscillation Concept
Isolation is the propagation loss value from the booster
’s output port to its input port.
For a wireless booster, insufficient isolation between donor and service antennas
will result in self-oscillation.
Figure 6
As shown in the above diagram, the donor antenna receives a RF signal
f1
from the
Donor BTS, after amplification by the booster with a gain G, the signal radiates out
via the service antenna. Part of
f1 (f1’)
radiates back towards the donor antenna
(due to side lobe characteristics of antennas) and is picked up by the donor antenna
again and goes through the amplification process again. Severe self-oscillation
issue result in poor signal quality and at times it can damage the booster
s’ amplifiers.
To prevent self-oscillation from occurring, the isolation value must be at least 15dB