User's Manual

SER

S MANUAL FOR BAND SELECTIVE REPEATERS

03P

User'sManual.doc Id.-No.:154999 Page 30 22-Jan-01

5.1.3. Antenna Isolation

Before setting the parameters of the repeater, ensure that the antenna isolation is

measured and optimized. The Safety-Gain-Margin (SGM) between the antenna

isolation and the maximum gain of the repeater is specified to +15 dB for all RF-

repeaters, i.e. the gain has to be -15 dB less than the isolation value of the antennas.

For better antenna isolation, ICE (Interference Cancellation Equipment) has been

developed for channel selective repeaters in the GSM900/1800 networks as well as

for PCS1900. ICE is specified for a SGM of –5 dB. Following example will show the

significant difference of a repeater with ICE-option compared to a repeater without

ICE-option.

Assumed case of a poor antenna isolation:

• Repeater without ICE

Antenna isolation: 80 dB

SGM: - 15 dB

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Allowed max. gain: 65 dB

In this case, the antenna isolation should be improved. The operator has to enlarge

the distance between both antennas or has to shield each antenna from the other.

Sometimes, it is difficult to enlarge the distance or to shield the antenna to reach the

necessary value.

The next example clarifies how to solve the antenna isolation problem with an ICE-

repeater. The SGM between the antenna isolation and the maximum gain is specified

to -5 dB, i.e. the gain can be +5 dB more than the isolation value of the antennas.

Assumed case of the same poor antenna isolation as in the previous example:

• Repeater with ICE-option

Antenna isolation: 80 dB

SGM with ICE-option: +5 dB higher

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Allowed max. gain: 85 dB

For further details to ICE or antenna isolation, please refer to MIKOM “Application

Note for Antenna Isolation” or “ICE Datasheet”.