J3 SeriesManual
7
Signalwing Corporation
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Add. : 4F, No. 41ABld, Huaide Cuigang No. 5 Industrial Park, Fuyong Street, Bao'an District, Shenzhen ,China 518103
2. Installation
2.1 Isolation
Isolation is an important concept for the repeater system, and it is one of the factors
that affect the location of the donor antenna and server antenna. In the repeater system,
the isolation must be enough, which means the donor antenna cannot be installed too
close to the repeater. But what is isolation? The isolation is the propagation loss between
the donor antenna and the service antenna which needs at least 15dB higher than the
gain value of the repeater. Non-compliance to this criterion would result in poor signal
quality or poor signal strength in the coverage area and the amplifier of the repeater may
also be damaged.
Isolation ≧Repeater Gain + 15 dB
2.1.1 Self-Oscillation Resistance
Self-oscillation is a phenomenon that would occur when the isolation for the repeater
system is not enough. In other words, insufficient isolation betweendonor and server antennas
would result in self-oscillation. Which means part of the signal that is being amplified by the
repeater radiates back towards the donor antenna and gotpicked up by the donor antenna and
went through the repeater amplification process again. Severe oscillation would result in poor
signal quality and even damage the repeater. Self-oscillation will deteriorate the signals inside
the coverage area and interfere towards the BTS.
2.1.2 The Isolation Value
The precise estimation of the isolation value can be obtained via a physical test
measurement. This test measurement is done at the actual environment where the donor
antenna and the server antenna are installed for a repeater system. The test
measurement procedures are as follows:
1. Connect the signal generator (SG) to the donor antenna and transmit a signal with a
frequency (For GSM900, uplink is 890~915MHz and downlink is 935~960MHz.
Choose frequency 920MHz to do the test. For DCS1800, uplink is 1710~1785MHz
and downlink is 1805~1880MHz. Choose frequency 1795MHz to do the test. For
WCDMA2100, system uplink is 1920~1980MHz and downlink is 2110~2170MHz.