What are Sector Antennas?

Antennas

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Editorial Team - everything RF

Jul 26, 2017

A sector antenna or "sector panel" is a is a directional outdoor antenna designed to radiate RF energy over a defined horizontal sector. They are most often used by cellular base stations and wireless access sites, easily recognizable as the long, narrow panels mounted on communication towers. Their geometry and internal design allow them to deliver high gain within a controlled azimuth range, allowing long-range and high-capacity coverage.

Sector antennas consist of an array of dipoles placed in front of a shaped reflector. The dipoles generate the RF energy while the reflector controls and narrows the beam into a specified azimuth width. The shape, size, and edge features of the reflector determine the antenna’s gain, sidelobe levels, and beam stability across the operating band. Because the aperture is vertically long and horizontally narrow, the antenna produces a strong, focused radiation pattern in the horizontal plane while maintaining a more controlled vertical pattern.

The size and shape of the reflector determines the performance of these antennas. The reflector is usually flat with some ridges or other features along the edges. A sector antenna is almost always categorized by its azimuth plane 3-dB beam width. They are commonly available with 60 degree, 90 degree, and 120-degree directionality. Smaller beamwidths generally offer higher gain and longer reach, whereas wider beams cover more area with reduced gain. Installation height also plays a significant role: antennas mounted higher above ground can serve larger zones but must be carefully downtilted to ensure that the main beam intersects the intended coverage area instead of overshooting it.

The main reflecting screen of the sector antenna consists of Aluminum and the antenna has a radome which is usually developed from a fiberglass material, this keeps the components inside the antenna safe and allows the antenna to withstand harsh weather conditions. Sector antennas are used extensively for cellular communication. The largest use of these antennas is for cell phone base-station sites.

The coverage area of sector antennas is determined by the projection of the radiation pattern on the ground, which can be adjusted by changing the down-tilt angle of the antenna. In some models this is done mechanically by manually adjusting the tilt of the antenna with an adjustable mounting bracket. In more recent sector antennas the pattern can be electronically tilted, by adjustable phase shifters in the feed of the individual dipole elements of the antenna. These are adjusted by a remote control circuit from the ground, eliminating the need for a technician to climb the antenna tower.

In cellular networks and point-to-multipoint systems, multiple sector antennas are mounted around the tower to create full 360° coverage. A three-sector configuration using 120° antennas is common in traditional networks, while deployments requiring higher capacity may use four 90° or even six 60° sectors. The number of sectors is chosen based on traffic demand, interference planning, and site layout.

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