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To implement a 4+0 XPIC, you will need as mentioned above one
Cross Polar antenna (dual polarized).
In each polar, you will connect a power splitter with two radios which
will give you 4radios in one antenna.
in the indoor part you will put your MMU3A as follows: the CH1 (first
frequency) will be used let us say in position 1 and 3 and will be
connected via XPIC cable(configured as 1+0 with XPIC and you have
to define the companion MMU position while configuring the MMU in
POS1 the companion MMU will be 3) and the Second frequency CH2
will be used in position 2 and 4 (interleaved positions) and as above
they will be interconnected by the XPIC cable and will be configured
as in the case of POS1 and 3.The IF cables coming from the radios
of the Vertical power splitter will be connected in POS 1 and2 and the
radios of the horizontal power splitter will be connected in POS 3 and
4 or vice versa.
9.1.3
Aligning Integrated Dual Polarized Antennas
This instruction is valid for integrated dual polarized antennas, 0.3 m (1 ft) and 0.6 m (2 ft).
The polarization alignment of integrated dual polarized antennas is performed in two steps:
Mechanical optimization: A primary, rough alignment performed at the far end antenna.
Cross Polarization Discrimination Optimization: A fine-tuning performed at the near end antenna to assure the best possible communication.
These two steps are described below.
Mechanical Optimization
Figure 220 Mechanical Adjustment
1. Loosen the two horizontal screws G on the polarization adjuster.
2. Use a spirit level and turn the nuts H on the link screw until the antenna is levelled.
3. Tighten the screws and the nuts.
4. Turn on the transmitter at far end, using vertical polarization.
Cross Polarization Discrimination Optimization
Figure 221 Rotational Alignment of the Antenna
1. Loosen the two horizontal screws G on the polarization adjuster. 2. Measure at near end on the RAU with horizontal polarization.
3. Use the alignment nuts H to rotate the antenna in the polarizational plane. The rotation is performed to minimize the leakage between the two
polarizations, that is, to maximize the cross polarization discrimination. 4. Record the measured value.
5. Measure at near end on the RAU with vertical polarization and record the value.
A cross polarization discrimination of at least 27 dB (AGC 0.675 V) must be reached. The value is the difference between the signals measured on the two radios.
If the reached value is less than 27 dB, perform step 2–5 again.
Note:
The maximum discrimination is reached within a narrow band, see Figure 222.
Figure 222 Polarization Discrimination
6. Tighten the alignment nuts when maximum discrimination is found.
9.1.4
Aligning Separately Installed Dual Polarized Antennas
This instruction is valid for separately installed dual polarized antennas, 0.3 m (1 ft) and 0.6 m (2 ft). For larger antennas, refer to the enclosed separate instructions. For 0.3 – 0.6 m antennas, an alignment according to Section 9.1.2 must first be performed.
The polarization alignment of separately installed dual polarized antennas is performed in two steps:
Mechanical optimization: A primary, rough alignment performed at the far end antenna.
Cross Polarization Discrimination Optimization: A fine-tuning performed at the near end antenna to assure the best possible communication.
These two steps are described below.
Mechanical Optimization
This procedure is only performed at the far end antenna.
Figure 223 Loosening the Feeder
1. Remove the screw in the non-slotted hole. The screw is not used when aligning separately installed dual polarized antennas.
Figure 224 Levelling the Feeder
3. Use a spirit level and turn the feeder until it is levelled.
Figure 225 Tightening the Feeder Screws
4. When the feeder is in level, tighten the screws to lock it in position. 5. Turn on the transmitter at far end, using vertical polarization.
Cross Polarization Discrimination Optimization
This procedure is only performed at the near end antenna.
Figure 226 Loosening the Feeder Screws
1. Remove the screw in the non-slotted hole.
Figure 227 Rotating the Feeder
3. Measure at near end on the RAU with horizontal polarization.
4. Rotate the feeder to minimize the leakage between the two polarizations, that is, to maximize the cross polarization discrimination.
5. Record the measured value.
6. Measure at near end on the RAU with vertical polarization and record the value.
A cross polarization discrimination of at least 27 dB (AGC 0.675 V) must be reached. The value is the difference between the signals measured on the two radios.
If the reached value is less than 27 dB, perform step 3–6 again.
Note:
The maximum discrimination is reached within a narrow band, see Figure 228.
Figure 228 Polarization Discrimination
Figure 229 Tightening the Feeder Screws
9.2
Transforming the Alignment Value
The figure below shows an alignment curve that transforms the alignment level in volts into RF input level in dBm.
Figure 230 RF Input Level as a Function of the Alignment Level Table 9 Accuracy with Voltmeter
-25 dBm to -30 dBm (1) ±0.075 V / ±3 dB
-30 dBm to -60 dBm ±0.065 V / ±2.5 dB
-60 dBm to -80 dBm ±0.075 V / ±3 dB
(1) Only MINI-LINK HC
Table 10 Accuracy with LCT, MSM or Displayed on the MMU
-25 dBm to -30 dBm (1) ±3 dB
-30 dBm to -60 dBm ±2 dB
-60 dBm to -80 dBm ±3 dB
(1) Only MINI-LINK HC
2. Compare the RF input level with the one specified in the installation data form (calculated for the system during path calculation) and check that the desired level is obtained.
