7/23/2019 XPD Aligment SoP

1/8

Aligning Dual-Polarized Antennas (XPD

adjustment)Aligning Dual-Polarized Antennas

1. Aligning Dual-Polarized Antennas

When aligning dual-polarized antennas, align the main lobes by adjusting the azimuth and elevation of

the antennas at both ends. Engineers also need to adjust the feed booms of the antennas so that cross-

polarization discrimination (XPD) meets requirements.

Prerequisites

The preceding site commissioning items have been completed at both ends of a microwave link.

The weather conditions at both ends are suitable for outdoor operations, and there is no threat of

rain, snow, fog or other unfavorable conditions that could interfere with the procedure.

Onsite conditions meet the requirements for antennas to work at their given heights, and the

commissioning personnel are trained to work at these heights.

A properly calibrated multimeter is available.

The automatic transmit power control (ATPC) function has been disabled (this function is disabled

by default).

The adaptive modulation (AM) function has been disabled (this function is disabled by default).

Tools, Equipment, and Materials

Adjustable wrench

Interphone

Hex key (delivered with antennas)

North-stabilized indicator

Telescope

Multimeter

Received signal strength indicator (RSSI) test cables (delivered with RTN 310)

Special spanner for the orthogonal mode transducer (OMT) (delivered with the OMT)

7/23/2019 XPD Aligment SoP

2/8

Context

NOTE:The following procedure assumes that the RTN 310s at both ends are installed separately from antennas.

If the RTN 310s at both ends need to be connected directly to an OMT, the OMT should be adjusted

instead of the antenna feed boom.

Procedure

1. Power off the vertically polarized RTN 310s and power on the horizontally polarized RTN 310s

at both ends of the microwave link. Ensure that the antennas at both ends are transmitting

horizontally polarized signals.

2. Adjust the azimuth angle and elevation angle of the antennas at both ends by referring to

Aligning Single-Polarized Antennas, and ensure that the main lobes of the horizontally

polarized signals are aligned.

3. Measure the received signal level (RSL) of the horizontally polarized signals, that is, P1, at the

local end.

7/23/2019 XPD Aligment SoP

3/8

a. Use a multimeter to measure the RSL at the RSSI port of the horizontally polarized RTN

310.

b. Calculate the RSL of the horizontally polarized signals, that is, P1, by referring to the

curve diagram delivered with the RTN 310.

4. Adjust the feed boom at the local end, and ensure that the RSL of the vertically polarized

signals reaches the lower threshold (P2).

a. Power on the vertically polarized RTN 310 at the local end.

7/23/2019 XPD Aligment SoP

4/8

b. Use a multimeter to measure the RSL at the RSSI port of the vertically polarized RTN

310.

c. Calculate the RSL (P2) of the vertically polarized signals by referring to the curve

diagram in the RTN 310 box.

d. Calculate the XPD1 (XPD1 = P1 - P2).

If... Then...

The calculated XPD1 is less than 24 dB Go to the next step.

The calculated XPD1 is greater than or equal to 24 dB Go to 5.

e. Release the feed boom holder slightly, and turn the feed boom slightly until the RSL

reaches the lower threshold and the calculated XPD1 is greater than or equal to 24 dB.

7/23/2019 XPD Aligment SoP

5/8

5. At both ends of the microwave link, power off the horizontally polarized RTN 310s and power

on the vertically polarized RTN 310s. Ensure that the antennas at both ends are transmitting

vertically polarized signals.

6. Measure the RSL (P3) of the vertically polarized signals at the local end by referring to 3.

7. Adjust the feed boom at the local end, and ensure that the RSL of the horizontally polarized

signals reaches the lower threshold (P4).

a. Power on the horizontally polarized RTN 310 at the local end.

7/23/2019 XPD Aligment SoP

6/8

b. Use a multimeter to measure the RSL at the RSSI port of the horizontally polarized RTN

310.

c. Calculate the RSL (P4) of the horizontally polarized signals by referring to the curve

diagram delivered with the RTN 310.

d. Calculate the XPD2 (XPD2 = P3 - P4).

If... Then...

The calculated XPD2 is less than 24 dB Go to the next step.

The calculated XPD2 is greater than or equal to 24 dB Go to 8.

7/23/2019 XPD Aligment SoP

7/8

e. Release the feed boom holder slightly, and turn the feed boom slightly until the RSL

reaches the lower threshold and the calculated XPD2 is greater than or equal to 24 dB.

7/23/2019 XPD Aligment SoP

8/8

8. Tighten all the screws on the antennas.

NOTE:

Use the multimeter to measure the RSL at the RSSI port again to ensure that no movement

occurred during the screw tightening process.

Related Information

In practice, you can align vertically polarized antennas first. If XPD can meet requirements after the

vertically polarized antennas are aligned, you do not need to align horizontally polarized antennas.

Otherwise, you need to go on to align the horizontally polarized antennas.

Table to be filled in after completing the XPD alignment:

.