Beamwidth

Beamwidth is the angular separation between the points in the main lobe that are down from the maximum gain by 3 dB. The angle is called the lobe angle. An antenna has horizontal beamwidth and vertical beamwidth, forming a horizontal lobe angle and a vertical lobe angle, respectively. Beamwidth is a key counter for directional antennas.

Figure 2-3 shows the radiation pattern of a directional antenna. The signal strength gradually increases from the blue area to the red area. Figure 2-4 shows the horizontal and vertical patterns, and beamwidth.

Figure 2-3 Antenna radiation pattern

Figure 2-4 Beamwidth

When the beamwidth is narrow, the radiation distance is long and the anti-interference capability is strong.

• When deploying antennas, note that side lobes interfere with peripheral residential areas. In most cases, main lobe radiation needs to be enhanced, and side lobe radiation needs to be suppressed. However, in the areas near the antennas, side lobes are needed to enlarge the coverage distance.
• H-plane half-power beamwidth determines the beamwidth of an antenna in the horizontal plane. When beamwidth is wide, good signal coverage is available at the sector boundary. However, when the downtilt angle becomes larger, beam distortion is more likely to occur, leading to overshoot coverage. On the contrary, when beamwidth is narrow, signal coverage is poor at the sector boundary. Increasing the downtilt angle can resolve this issue to a certain degree, which can prevent overshoot coverage. Base stations in the downtown are deployed at short intervals and have antennas with large downtilt angles installed. In this case, antennas with small H-plane half-power beamwidth are recommended. In the suburbs, antennas with large H-plane half-power beamwidth are recommended.
• V-plane half-power beamwidth determines the beamwidth of an antenna in the vertical plane. When beamwidth is narrow, signals that deviate from the main beam attenuate fast. In this case, it is easier to control the coverage by adjusting the downtilt angle, therefore improving coverage quality for cells.