User Manual

Verizon Wireless MPE25K RF Repeater
User Manual V0.3
Advanced RF Technologies, Inc. Proprietary Document 19/59
2.3.4 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.
A sufficient isolation value is 13 ~ 15 dB greater than the maximum gain of the
repeater. For example, if the gain of the repeater is 50 dB, then an isolation of
63 ~ 65 dB or greater is required. In the same manner, because the ADRF-25K
has a maximum gain of 80 dB, it requires an isolation of at least 93 ~ 95 dB.
Figure 9 - RF Repeater Oscillation