Gmsk Carrier Units (Gcu); Duplexer Amplifier Multi Coupler (Duamco) - Siemens BS-240 Technical Description

Information
Base Station System
3.4
3.5
A30808-X3247-L14-2-7618

GMSK Carrier Units (GCU)

The GCU is a resembled ECU (the main sub-units are similar) which supports GMSK
modulation only, like the CU.
GCUs and CUs differ in the RF output power value for the GSM 1800 frequency band:
GCU: 53,7 W; CU: 37,1 W.
There are different variants of GCUs for the frequency bands GSM 900 and GSM 1800.
The types of GCU are the following:
•
GCUGV2 GMSK Carrier Unit for GSM 900 MHz
•
GCUDV2 GMSK Carrier Unit for GSM 1800 MHz
Duplexer Amplifier Multi Coupler (DUAMCO)
The DUAMCO consists of two identical modules. Each module contains a duplex filter,
which combines the RX and the TX path together, to be fed to a common antenna. The
DUAMCO combines 1 (see
carriers to one antenna and consists of two branches with the following elements:
•
a LNA (Low Noise Amplifier) which takes care of a low system noise figure
•
an attenuator (in case of installed TMAs, additional gains greater than the cable
losses must be adjusted by means of the attenuator)
•
a second low noise amplifier
•
a power splitter which distributes the received band to the CUs (Carrier Units)
•
a transmit path which consists of:
– an isolator which protects the PAs (Power Amplifiers) inside the CUs from each
other in order to assure the required intermodulation suppression
– a hybrid coupler which provides the reference signal for dynamic and static power
control. The corresponding not transmitted power is terminated in a load including
a heat sink (for DUAMCO 4:2 and DUAMCO 8:2)
– an ASU (Antenna Supervision Unit) which is responsible for detecting certain
reflection factors at the antenna connector. The ASU detects the VSWR failure
and generates a failure information towards the O&M (CAN bus interface). This
information is subdivided in several levels with the following characteristics:
- VSWR < 2 neither generation of warning nor of an alarm
- 2 ≤ VSWR ≤ 3 generation of warning 'Antenna not Adjusted'
- VSWR > 3 generation of VSWR alarm 'Antenna Faulty'.
and a common part consisting of:
•
a PDU (Power Distribution Unit) for two TMAs (Tower mounted Amplifier) connected
to the TMAs by means of an antenna feeder cable
•
an O&M interface which transmits error messages to the BTS core via a slow O&M
bus (CAN bus)
The DUAMCO amplifier has two different operation modes:
– the AMCO mode where no TMA is used
– in case a TMA is used the DUAMCO is configured in the MUCO mode
The PDU provides the DC power supply and the alarm supervision of the TMAs. Alarm
monitoring is done with a signalling interface between DUAMCO and TMA, modulated
onto a IF carrier at 7.86 MHz.
Fig. 4.2), up to 2 (see
Technical Description (TED:BSS)
Fig. 4.3) or up to 4 (see
BS-240/241
Fig. 4.4)
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