User's Manual

Doc. No.
Rev.
Date
1.00
2011-12-08
Damm Cellular Systems A/S, Denmark
TETRAFLEX
®
V7.5 MANUAL - TR412 Transceiver Description
TetraFlex® 7.5 Manual 4-17
The Base Station is provided with an RF Test Loop feature allowing extensive test of the
whole Base Station both locally and remotely without any additional equipment.
Each TR41x is provided with an RFTL output (BNC connector) on the front plate. The output
can be activated with either a high level output (-40dB relative to the TX output connector),
low level output (-50dBr) or turned off (<-80dBr).
The output signals are either combined in RFTL combiner modules and brought to the AI411
RFTL inputs (4- and 8-carrier versions) or brought directly to the AI411 inputs (2-carrier
versions).
In the AI411 the two inputs are combined, followed of and attenuator/jumper to compensate
for the loss of the external combiner. This setting always follows the similar settings in the
RM.
Afterwards follows a variable attenuator adjustable through the AI411 front hole marked IN.
This attenuator is used to compensate for output power selection of the TR41x.
The signal now enters a double balanced mixer, where the frequency is converted from the
TX band to the RX band. A Crystal oscillator running on the RX/TX duplex frequency offset
provides the injection signal.
The mixer is followed of a HPF and a buffer amplifier before it reaches the variable output
attenuator, accessible from the front of the AI411 through the hole marked OUT. This
attenuator is used to compensate for actual cable loss of the TEST feeder going to the TMA.
A combining circuit at the output connector allows the insertion of an external test signal from
the BNC connector on the AI411 front plate marked TEST IN.
At the output connector a DC control signal insertion circuit is provided to the TMA, together
with an over-voltage arrestor.
From the TNC output connector on the rear of the AI411 the test signal is connected
internally in the BS to the N-female TEST connector on the BS top, from where it goes to the
TMA in the top of the mast with a feeder similar to the RX feeders.
The TEST input in the TMA is also provided with an over-voltage arrestor and a DC
separation circuit.
In the TMA the test signal is divided in two, one for the A-path and one for the B-path. The
test signal is then inserted in either the forward direction of the two paths to the BS (-50dBr)
or optionally in the reverse direction against the antennas (-40dBr).
The direction is controlled of the DC signal in the TEST feeder and reverse direction can be
activated of each of the TR41x, when RX antenna return loss measurement is performed.