Analysis of a GSM base station antenna near conductive object: far field pattern distortion

In the real life, antenna is not placed in the free space. It is backed by a pole, wall or other structure, and often surrounded by other conductive objects in the immediate vicinity. Modern GSM base stations even employ configurations of multiple antennas per sector, where two antennas are placed so close that they can scatter each other´s radiation. This work shows how conductive objects in the close proximity of the antenna can significantly distort the radiation pattern of the antenna. GSM operators should take this effect into account, since antenna gain can vary a few dB in the boresight direction, and even more in the other directions of the main lobe. The manufacturer-provided radiation pattern for antenna in free space should then be considered with added uncertainty. Results suggest that pattern distortion effect could be employed deliberately if needed, adding a simple rod or reflector in the vicinity of the antenna, to add a few dB in wanted direction.