Purpose: This is a simple document to help on the antennas alignment with XPIC XPD, here is the steps for a simple and quick way, as well alerting for the most common problem.
Alignement 1. Mechanical optimization 1. Make sure the function Automatic Transmitter Power Control (ATPC) is turned off during alignment. 2. Adjust the antenna for maximum alignment value. 3. Tighten the locking screw when maximum value is achieved. 4. Repeat steps 2 to 3 until the maximum alignment value is achieved. 5. Measure the alignment level and record the value. 6. Verify if the RX level is according to the Call Off.
Make sure all screws are tightened when the alignment procedure is finished.
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2. Cross Polarization Discrimination Optimization (XPD) Minimum XPD within the 1 dB co-polarized contour: * 06 – 13 GHz 30 dB * 15 – 38 GHz 27 dB 1. Turn on the transmitter on near & far end, using vertical polarization. 2. Turn off the transmitter on near end, horizontal polarization. 3. Measure with a voltmeter at near end on the RAU with horizontal polarization. 4. Align the antenna until the worst voltage value found. The rotation is performed to minimize the leakage between the two polarizations, that is, to maximize the cross polarization discrimination. 5. Verify the RX Level at near end in horizontal polarization and record the measured value. 6. Verify the RX level at near end in vertical polarization and record the value. 7. 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. 8. There should be a difference of 27 dB b/w H and V rx level (ex: V pol rx level: 30dB; H pol rx level: -57dB, with V Tx pol ON and H pol Tx OFF). 9. If the reached value is less than 27 dB, perform step 2 to 5 again. 10. Tighten the feeder screws when maximum discrimination is found.
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Polarization adjustment 1. Slightly loosen 2pcs of polarization screws. 2. Adjust polarization by turning radio interface (OMT) ±5°. 3. Tighten 2pcs of polarization screws with 24Nm ± 5% (17Nm if A2-70). Polarization screws, 2pcs Polarization -5° Polarization +5°
Polarization screws, 2pcs
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Integrated Installation 2+0 XPIC
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Polarization -5°
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Polarization +5°
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2.1 Antenna before XPD Alignment. 2.1.1 Antenna with maximum value according to the RSL in call off.
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2.1.2 Vertical & Horizontal TX ON Link Aligned with RxL as per Call Off. Polarization: Vertical
Polarization: Horizontal
2.1.3 Vertical TX ON & Horizontal OFF Polarization: Vertical On
Polarization: Horizontal Off
With 33.0dB different between Horizontal and Vertical.
2.1.4 Vertical TX OFF & Horizontal ON Polarization: Vertical Off
Polarization: Horizontal On
With 33.9dB different between Vertical and Horizontal.
Nominal point between Horizontal and Vertical is 33.0 / 33.9dB before XPD Alignment.
2.2 Antenna after XPD Alignment. 2.2.1 Antenna with maximum value according to the XPD RSL.
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2.2.2 Vertical TX ON & Horizontal OFF Polarization: Vertical On
Polarization: Horizontal Off
With 27.0dB different between Horizontal and Vertical.
2.2.3 Vertical TX OFF & Horizontal ON Polarization: Vertical Off
Polarization: Horizontal On
With 27.9dB different between Vertical and Horizontal.
New nominal point between Horizontal and Vertical is 27.0 / 27.9dB after XPD Alignment. ~ END MOP ~
