User’s manual for Remote Unit MOR801B Power
M0070A0A.doc
Id.-No 151155
Page 15
18-June-99
2.1 General
The Repeater consists of two amplifier chains. The signals to and from the mobiles are
combined to an antenna by a frequency separation unit, denominated in the following as
Duplexer. The optical signals to and from the Master Unit are converted by the Optical
Transceiver.
In the Downlink direction the optical signals from the Master Unit are converted into RF-
signals by the Transceiver (see chapter 2.7). They pass the 4-way-Splitter (see chapter2.9),
which provides the RF-signal for the RF modules. After the RF module (see chapter 2.2) they
are combined by the Active Combiner (see chapter 2.6) and afterwards amplified by the Feed
Forward Amplifier (see chapter 2.12), which provides the required output power. Finally the
signals are fed to the antenna by the Duplexer (see chapter 2.5).
In the Uplink direction the signals from the mobiles are seperated by the Duplexer, get to a
Pre-Amplifier and afterwards to an RF module. The signals are combined by the Active
Combiner then, get converted into optical signals by the Transceiver (see chapter 2.7) and are
finally transmitted to the Master Unit.
In the final amplifier of the Downlink a power detection measures the output power and
controls the gain. In the Uplink the gain is controlled by the Active Combiner to protect the
Optical Transceiver. This power detection is called Automatic Level Control (ALC) (see
chapter 3.3).
2.2 RF modules
The task of the RF modules is to amplify the receive signals and to convert them into an
intermediate frequency. The signals, then, proceed a filter stage comprising of highly selective
filters, and run through a digital controllable attenuator. The attenuation can be set in steps of
2 dB, locally or remotely. By using the same synthesizer frequency, that was used to convert
the signals down to intermediate frequency, the intermediate frequency is mixed up to the
original frequency.
The synthesizer is controlled via an I²C-Bus. In case of a breakdown in mains, gain and
frequency data are non-volatile stored in an EEPROM on board.
See figure 2-2 Top view of an RF module for an exemplary channel or band module.