User's Manual

Doc. No.
Rev.
Date
1.00
2011-12-08
Damm Cellular Systems A/S, Denmark
TETRAFLEX
®
V7.5 MANUAL - RX Multi coupler for BS41x
TetraFlex® 7.5 Manual 4-16
obtained before reaching the first amplifier. The filter also ensures good rejection of signals
from other transmitters in the same mast.
The filter is followed of an LNA with a GaAs PHEMT transistor with simultaneous very low
noise figure and high IM intercept point.
The amplifier output goes to the N-female output connector, where the DC-feed from the BS
to supply the amplifier is extracted. An over-voltage arrestor is provided on the connector to
protect the amplifier during lightning.
The RX signal is then going from the TMA to the RX input connector on top of the BS through
the RX feeder, and further internally in the BS to the RM input of rear side of the AI411
Antenna Interface Unit.
The AI411 input is also provided with an over-voltage arrestor. After passing the DC insertion
circuit, the RX signal passes a directional coupler, which can be used to provide a test input
signal through the TNC connector on the AI411 front plate.
Afterwards follows the attenuator used to balance the RX feeder loss, adjustable through the
hole in the front plate marked “Gain”.
The signal is amplified in a low-noise high dynamic range transistor to compensate for the
following splitters. The AI411 is provided with two outputs coming from a 2-way Wilkinson
splitter.
The two outputs can either feed up to eight TR41x through external splitters with 13dB
insertion loss (used in 4- and 8-carrier BS versions) or feed two TR41x directly (used in the 2-
carrier BS version).
A jumper internally in the AI411 changes the output level with 13 dB to compensate for the
splitter. The actual setting of this jumper is marked outside the AI411 besides the type plate.
4.3.3 Supply and alarm circuits
Each RX path is provided with independent voltage regulators to feed the TMA and RM
amplifiers.
The TMA DC feed is provided with circuitry to detect low-current alarm (no TMA connection)
and low-voltage (TMA connection short-circuit).
Similarly the RM amplifier is provided with circuitry to detect low-current and high-current
alarms.
The alarms are connected to the BSC and send to the TR41x’s assigned to the particular
Radio Cell. If faults exist in one leg only, a warning alarm is generated. If alarms exist in both
legs, a blocking alarm is generated.
4.3.4 RF Test Loop path description