Azimuth pattern design to reduce interference in overlapping sectors using combined tilt

Recently the number of applications requiring high throughput in 3G mobile communication networks has increased. As a result, the amount of traffic especially in urban areas has increased, requiring a high system capacity. To secure the system capacity, a sector cell configuration is generally applied. However, since the azimuth beam patterns of conventional base station antennas have moderate curve characteristics, overlapping the areas between adjacent sectors causes degradation in the system capacity due to inter-cell interference. This interference can be decreased by shaping the beam in the azimuth plane. To achieve such shaped beam antennas, additional exciting or parasitic elements, or both are required, resulting in large and complex antennas. This paper investigates a simple method to shape the beam of the base station antennas in the azimuth plane. Shaped beams are achieved by combining mechanical up-tilt and electrical down-tilt. The 3-dimensional radiation property of the antenna is utilized to shape the beam to cover the service area. The advantage of this method is that the conventional base station antenna configuration can be used as the antenna. However, there are some limitations when applying this to a practical scenario. We especially focus on the antenna gain toward the service area and clarify the design criteria of the array antenna. We also show the effectiveness under these conditions. This paper is organized as follows. First, the fundamental characteristics are described when employing the combination tilt. Then, the design criteria are derived for the base station array antenna in order to maintain the antenna gain toward the service area. Finally, the effectiveness of the antenna design is described.