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IN-FIELD TEST OF MACROCELL ANTENNS FOR TILT AND PARTIAL RADIATION PATTERN

IP.com Disclosure Number: IPCOM000007724D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-17
Document File: 3 page(s) / 184K

Publishing Venue

Motorola

Related People

B. Mohebbi: AUTHOR

Abstract

The measurement technique described here would dramatically simplify the task of establishing a macrocell antenna tilt and partially identify the antenna radiation characteristics in azimuth and ele- vation. Often the antennas installed in macrocell sites are too large to be tested individually in a suit- able environment such as anechoic chambers. The few antennas that are tested for radiation character- istics, usually have the test in a calibrated field where there are no objects in the vicinity of the antenna effecting the radiation characteristics, Therefore the antenna radiation characteristics on a practical mast, often in the vicinity of many other antennas and obstacles, would be different from that supplied by the manufactures. There is also the added problem of faulty antennas, tolerances and variations due to the manufacturing process which may alter the antenna behaviour from the specified one. Part of the cell planning is cell site antenna tilt. This tilt determines the coverage area of the cell and is one of the parameters in cell design. Although there are electrical, electromechanical and mechanical tilting mechanisms in operation now, on occasions it is desirable to establish the antenna tilt of a suspect sector which may be interfering with cochannel cells, or not covering the cell area according to plan. The aim of this technique is to establish the tilt and radi- ation pattern of a macrocell antenna, installed and operational at the cell site, as easily as possible.

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Technical Developments

IN-FIELD TEST OF MACROCELL ANTENN& FOR TILT AND PARTIAL RADIATION PATTERN

by B. Mohebbi

  The measurement technique described here would dramatically simplify the task of establishing a macrocell antenna tilt and partially identify the antenna radiation characteristics in azimuth and ele- vation. Often the antennas installed in macrocell sites are too large to be tested individually in a suit- able environment such as anechoic chambers. The few antennas that are tested for radiation character- istics, usually have the test in a calibrated field where there are no objects in the vicinity of the antenna effecting the radiation characteristics, Therefore the antenna radiation characteristics on a practical mast, often in the vicinity of many other antennas and obstacles, would be different from that supplied by the manufactures. There is also the added problem of faulty antennas, tolerances and variations due to the manufacturing process which may alter the antenna behaviour from the specified one. Part of the cell planning is cell site antenna tilt. This tilt determines the coverage area of the cell and is one of the parameters in cell design. Although there are electrical, electromechanical and mechanical tilting mechanisms in operation now, on occasions it is desirable to establish the antenna tilt of a suspect sector which may be interfering with cochannel cells, or not covering the cell area according to plan. The aim of this technique is to establish the tilt and radi- ation pattern of a macrocell antenna, installed and operational at the cell site, as easily as possible.

  The existing technique of obtaining the radia- tion characteristics oflarge aperture antennae, such as those used in macrocells, is to place the antenna in a calibrated field, where the path loss from the antenna to the receiver is previously established. This field has to be isolated so the antenna pattern is not affected by other obstacles. In any event, the ground reflection has to be taken into account and compen- sated for. In order to find the radiation pattern in both azimuth and zenith angles, the antenna under test is then rotated in every possible angle (0,~)

recording the receive power at the receiver site. This technique is useful for obtaining the radiation pat- tern in isolation. However its short coming is that it does not provide any indication of how the antenna pattern is modified in the field, at different cell sites. As the antenna behaviour is highly dependent on the ground and its surroundings, it is not possible to test the antenna for every possible operation sce- nario. The in-field measurements of macrocell anten- nas radiation pattern is limited and difficult. It usu- ally is limited to one plane, azimuth, with the elevation pattern totally ignored. Inability to meas- ure the elevation pattern effectively means that the antenna tilt has to be established by the inspection of antenna bracket and mounting. While th...