User's Manual

PN 8100-40 Help Hot Line (U.S. only): 1-800-530-9960 7-45
620004-0 Rev. B
Connecting a Main Hub to a Base Station
7.5.1 Attenuation
Figure 7-3 shows a typical setup wherein a duplex base station is connected to an
LGCell. For a simplex base station, eliminate the circulator and connect the simplex
ports of the base station to the simplex ports of the Main Hub. Add attenuators to reg-
ulate the power appropriately.
Figure 7-3 LGCell to Duplex Base Station or Repeater Connections
Duplex
Base Station
LGCell
Main Hub
Forward
Reverse
A3
A1
A2
• A typical circulator has an IP3 of +70dBm. If you drive the circulator too hard it will produce
intermods that are bigger than the intermods produced by the LGCell. Depending on the
LGCell model, the IP3 at the Forward port input of the LGCell can be as high as +30 dBm.
The IP3 of the circulator at that same point (i.e., following attenuator A1) is +70dBm – A1.
Thus, to keep the system IP3 from being adversely affected by the circulator, attenuator A1
should be no more than 35 dB.
• A filter diplexer can be used in place of the circulator. The IP3 of the diplexer can be
assumed to be greater than +100 dBm. If a diplexer is used, A3 can be omitted.
• A1+A3 should be chosen so that the output power per carrier at the RAU’s output is correct
for the number of carriers being transmitted. Suppose the base station transmits 36 dBm
per carrier and it is desired that the RAU output be 6 dBm per carrier and the forward port
gain is 0 dB. Then A1+A3=30 dB.
• A2+A3 should, ideally, be at least 10 dB less than the noise figure plus the gain of the
LGCell. For example, if the reverse port has a 0 dB gain (it does for all current LGCell mod-
els) and if there are eight RAUs, the noise figure (depending on the LGCell model) is
approximately 25 dB. So A2+A3 should be about 10 to 15 dB. If A2+A3 is too large, the
uplink coverage distance can be severely reduced.
• Given these three equations:
A1 ≤ 35 dB
A1+A3 = 30 dB (in this example)
A2+A3 = 10 dB (in this example)
we could choose A2=20 dB, A2=0 dB, A3=10 dB for this example.
or
Repeater