User's Manual

FIPLEX • Electromagnetic Devices for Radiocommunication Systems
FIPLEX BIDIRECTIONAL AMPLIFIER - USER MANUAL
Automatic Gain Control (AGC)
Automatic Gain Control circuitry is intended to keep repeater’s output power at a
fixed level when input signals exceed maximum values, avoiding quality signal degradation
by intermodulation generation.
Signals received from mobiles have a different nature that the ones received from
donor site or BTS, so it is rare that “AGC ON Uplink” led keeps on, if this occur, repeater
gain should be decreased. Is a good practice to set identical gain values in both (uplink
and downlink) paths to keep a good link budget balance, so is very recommended to take
downlink manual gain value as a reference for the uplink path. This balanced operation
mode prevents BTS desensitation or saturation from uplink signals amplified by the
repeater.
Overload Protection
When the automatic gain control circuit reaches its limit (20 dB), the power
amplifier stage is shut down to prevent harmful distortion and potential damage to the
repeater. After approximately ten seconds the system checks if overload condition is still
present, if this happens amplifiers will remain off. This cyclic check will continue until
condition that makes AGC circuitry reach its limit desapears.
Conditions that can cause AGC to reach its limit include the presence of one or
more very strong channels, a strong in-band noise source, or amplifier oscillation due to
poor antenna isolation.
When overload protection is active led labeled “OVERLOAD UPNLINK” is on.
15 Document FIP-BDAM-07-EN