User's Manual

Navini Networks, Inc. Ripwave Base Station I&C Guide
112
There are upper and lower limits to the TX Power and RX Sensitivity to which a BTS can be set.
One of the two conditions that determine the Maximum amount of power that can be delivered at
the antenna elements (Max TX Power
1
) is how much power can be output by the each one of the
PAs. The losses in the RF paths are: (1) the BTS Loss introduced by the Standard Filter, if used,
or by the Bypass Cable, if no filter is used; (2) The loss on the RF Cable (Main + Higher and
Lower Jumper cables + 6 terminators and lightening arrestors, estimated as 0.6 dB); and (3) the
loss at the base of the RFS, between the N-type connectors where the RF & Cal cables are
connected and the SMA connectors at the bottom of the Cal Board.
Max Tx Power
1
= Max PA Output
– BTS Loss [Formula 1]
– RF Cable Loss
– RFS Loss
The other condition is related to the Calibration process. During the calibration of the TX paths
(one at a time), a fraction of the power delivered by the a PA to the corresponding antenna
element is derived through the Cal Board to the common CAL cable and through the BTS back
plane until it arrives at the SYN card. The Calibration process requires that the Input Power
received by the SYN card be in a certain range. Lets find a formula for the Max TX Power
2
(power at the antenna elements) that would allow the system to be calibrated. Above this level
the input power received by the SYN card would be over the maximum allowed.
Therefore,
Max SYN Card Input = Max Tx Power
2
– Min Cal Board Loss
– CAL Cable Loss
– Back Plane Loss
or
Max Tx Power
2
= Max SYN Card Input
+ Min Cal Board Loss [Formula 2]
+ CAL Cable Loss
+ Back Plane Loss
As both conditions must be satisfied, we take the most restrictive one, that is, the one that
produces the lower value:
Max Tx Power = Min { Max Tx Power
1
, Max Tx Power
2
} [Formula 3]
Substituting the Min SYN Card Input for the Max SYN Card Input and the Min Cal Board Loss
for the Max Cal Board Loss in Formula 4 we get the formula for the Min TX Power (at the
antenna elements) that allows the system to be calibrated. Below this level the input power
received by the SYN card would be less than the minimum required.