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Dual Band ICS Repeater User Manual
loss between the antennas needs to be at least 15dB above the DL gain value used by the
repeater. The R8XDLI series repeater is also known as the ICS repeater. Therefore, the Isolation
requirement is different from normal RF repeaters. For the normal RF repeaters the Isolation
value needs to be at least 15dB above the gain value. As for the R8XDLI series repeater, the
Isolation requirement is 15dB lower than the DL gain. Hence, the Isolation requirement for the
R8XDLI series is 30dB lower than ordinary Isolation requirement. Non-compliance to this
criterion can result in poor signal in the coverage area and may damage the amplifier of the
repeater.
3.2.3.1 Self-oscillation Concept
Isolation is the propagation loss value from the repeater
’s output port to its input port. For a wireless
repeater, 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 Node
B/eNode B, after amplification by the repeater 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
repeaters’ amplifiers. To prevent self-oscillation from occurring, the isolation requirement mention
previously must be met.
When self-
oscillation occurs, the alarm LED, “AGC Alarm” will be flickering. Repeater may be
damaged if it operates under self-oscillation condition.
3.2.3.2 Obtaining the Isolation Value
Isolation detection of the repeater
Isolation ≥ (DL Gain of Re 15dB) – 30dB
