2. Installation
2.1 Isolation
Isolation is an important concept for the repeater system, and it is one of the factors that affect the loca-
tion of the donor antenna and the location of the 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 server antenna
which needs to be at least 15dB higher than the gain value of the repeater. Non-compliance to this crite-
rion 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 between donor 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 got picked up by the donor antenna and went through the repeater amplification
process again. Severe oscillation issue would result in poor signal quality and at times it can even damage
the repeater amplifiers. 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
1 Connect the signal generator to the donor antenna and transmit a signal with a frequency. Choose
frequency 1995MHz to do the test. In simple words, choose the idle frequency of the system to do the
test) of certain power level from the signal generator.
2 Connect the spectrum analyzer to the server antenna and scan for the known frequency (The fre-
quency used by the signal generator). Mark the received power level on the spectrum analyzer.
3 Subtract the power level received at the spectrum analyzer from the output power (OP) level of the
signal generator to obtain the isolation value.
Isolation (dB) = Output Power from the signal generator – Received Power on the spectrum analyzer
Transmit a strong Output Power from the Signal generator is recommended (excess of 20dBm) for easy
recognition and detection by the spectrum analyzer.
2.2 Precautions and Preparation
1 Ensure the power applied to the repeater is within its working range. A separate circuit breaker is
recommended.
2 Ensure the donor antenna is installed at the location where signal from the donor BTS (Node B) is
good enough.
3 Ensure there’s sufficient isolation between the donor and server antenna.
4 The repeater is designed for indoor application. Ensure the location of the repeater is dry and
ventilated.
5 Ensure there are adequate resources to handle the weight of the repeater. 6. Some electronic parts
contain carcinogenic constituents, please handle the repeater with care, and discard the in a safe place
if necessary.
