Antenna Separation/Isolation; Figure 4-3 Rf Repeater Oscillation - ADRF SDRX-43-BTF User Manual

4.3

Antenna Separation/Isolation

Separation between the antennas is necessary to prevent oscillation. Oscillation occurs when the signal
entering the system continually reenters, due to the lack of separation between the donor and server
antennas. In other words, the signal is being fed back into the system. This creates a constant amplification of
the same signal. As a result, the noise level rises above the signal level.
To prevent feedback, the donor and server antennas must be separated by an appropriate distance to
provide sufficient isolation. Isolation is attained by separating antennas a sufficient distance so that the output
of one antenna does not reach the input of the other. This distance is dependent on the gain of the repeater.
The recommended isolation value is 20dB greater than the maximum gain of the repeater. For example, if
the gain of the repeater is 50 dB, then an isolation of 70dB or greater is required. In the same manner, because
the SDRX-43-BTF has a maximum gain of 95dB in case of SDRX-43-BTF, it requires isolation of at least 115dB.
Advanced RF Technologies, Inc.
SDRX-43-BTF
CPL(-40dB)
AC IN
SERVER
BATTERY
SERVICE
HOST
LAN0
REMOTE
LAN1
DONOR
CPL(-20dB)
Figure 4-3 RF Repeater Oscillation
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