User's Manual

User Handbook L-RU Revision C
CONFIDENTIAL
PROPRIETARY
Reg. No.: User Handbook 1100182-C.DOC Page 15 of 29
The ALC compensates for different uplink input levels per carrier providing optimised UL
performance with regard to spurious free dynamic range.
3.2.2 Downlink
The downlink path includes a five-stage amplifier with balanced power amplifier, filters and
an ALC, which automatically operates the RU according to ETSI requirements. The
downlink path is equipped with a monitoring to control the RF-amplifiers. Each amplifier
stage can generate an alarm by controlling the DC-current.
3.2.3 Monitoring
All amplifier stages in downlink and uplink as well as the optical transceiver are monitored.
Failures are logically combined to a resulting summary alarm that results in a switch-off of
the pilot tone.
The alarm matrix of the RU is shown in Table 1 below.
Alarm LED OK Failure
Power supply Main Power green Off
Summary alarm (RF am-
plifiers, optical modules)
Monitoring green red
Table 1 – Alarm matrix of the RU
3.2.4 Function of ALC
The main part of this ALC system is a detector circuitry. It converts an RF signal to an
equivalent DC voltage at its output. The detected voltage is compared with a reference
value adjusting an electrical controlled attenuator. Thus, the RF power level at the antenna
port is kept constant to maximum and no manual leveling is required.
3.2.5 Duplexer
The duplexer at the antenna port is a high performance ceramic duplexer separating uplink
and downlink RF-bands.