ADC Telecommunications Inc. F0684-112 Manual Do Utilizador
Connecting a Main Hub to a Base Station
6-38
InterReach Fusion Wideband Installation, Operation, and Reference Manual
CONFIDENTIAL
D-620616-0-20 Rev F
RAU inputs to the base station inputs. This SNR can not be better than the SNR of
Fusion Wideband by itself, although it can be significantly worse.
Fusion Wideband by itself, although it can be significantly worse.
A good rule of thumb is to set the uplink attenuation such that the noise level out of
Fusion Wideband is within 10 dB of the base station’s sensitivity.
Fusion Wideband is within 10 dB of the base station’s sensitivity.
6.8.2
RAU Attenuation and ALC
The RAU attenuation and ALC are set using the AdminBrowser Edit Unit Proper-
ties screen.
ties screen.
Embedded within the uplink RF front-end of each Fusion Wideband RAU band is an
ALC circuit. This ALC circuit protects the Fusion Wideband system from overload
and excessive intermodulation products due to high-powered mobiles or other signal
sources that are within the supported frequency band and are in close proximity to the
RAU.
ALC circuit. This ALC circuit protects the Fusion Wideband system from overload
and excessive intermodulation products due to high-powered mobiles or other signal
sources that are within the supported frequency band and are in close proximity to the
RAU.
Each individual Band (1or 2) of a Fusion Wideband RAU has an uplink ALC circuit
that operates as a feedback loop. A power detector measures the level of each band’s
uplink RF input and if that level exceeds –30 dBm, an RF attenuator is activated. The
level of attenuation is equal to the amount that the input exceeds –30 dBm. The fol-
lowing sequence describes the operation of the ALC circuit, as illustrated in
Figure 6-2.
that operates as a feedback loop. A power detector measures the level of each band’s
uplink RF input and if that level exceeds –30 dBm, an RF attenuator is activated. The
level of attenuation is equal to the amount that the input exceeds –30 dBm. The fol-
lowing sequence describes the operation of the ALC circuit, as illustrated in
Figure 6-2.
1.
The RF signal level into either Band of the RAU rises above the activation thresh-
old (–30 dBm), causing that ALC loop to enter into the attack phase.
old (–30 dBm), causing that ALC loop to enter into the attack phase.
2.
During the attack phase, the ALC loop increases the attenuation (0 to 30 dB) until
the detector reading is reduced to the activation threshold. The duration of this
attack phase is called the attack time.
the detector reading is reduced to the activation threshold. The duration of this
attack phase is called the attack time.
3.
After the attack time, the ALC loop enters the hold phase and maintains a fixed
attenuation so long as the high-level RF signal is present.
attenuation so long as the high-level RF signal is present.
4.
The RF signal level drops below the release threshold (–45 dBm) and the ALC
loop enters the release phase.
loop enters the release phase.
5.
During the release phase, the ALC loop holds the attenuation for a fixed period
then quickly releases the attenuation.
then quickly releases the attenuation.
An important feature of the ALC loop is that in Step 3, the attenuation is maintained
at a fixed level until the signal drops by a significant amount. This prevents the ALC
loop from tracking variations in the RF signal itself and distorting the waveform
modulation.
at a fixed level until the signal drops by a significant amount. This prevents the ALC
loop from tracking variations in the RF signal itself and distorting the waveform
modulation.