Sector Antennas
What are sector antennas?
A sector antenna is a directional microwave antenna with a sector radiation pattern. Typical designs are 60°, 90°, and 120°, often with a few extra degrees. The greatest use for these antennas is as antennas for cellular base station sites. They are also used for other types of mobile communications, for example in WiFi networks. They are used for limited distances of about 4 to 5 kilometers.
Sector antenna structure
At the bottom of the sector antenna, there are RF connectors for the coaxial cable (feedline) and an adjustment mechanism. For its outdoor arrangement, the main reflector screen is made of aluminum and all internal components are housed in a fiberglass radome shell to keep it operationally stable regardless of weather conditions.
Sector antenna grounding
Grounding is very important for outdoor antennas, so all metal parts are DC grounded.
Sector antenna shape
The long narrow shape of the antenna causes it to form a fan-shaped radiation pattern, wide in the horizontal direction and relatively narrow in the vertical direction. Based on the radiation pattern depicted, a typical antenna used in a three-sector base station has a horizontal beamwidth of 66°. This means that the signal strength in the ±33° direction is halved from its peak at the center (3 dB down). In the ±60° direction, which is suggested to be the boundary of a sector, the antenna gain is negligible there.
Sector antenna vertical beamwidth
The vertical beamwidth is no greater than 15°, 7.5° in each direction. In contrast to antennas used for commercial broadcasting (e.g., AM, FM, and TV), which must achieve a certain distance at which they can be listened to, a downward beam tilt, or downward inclination, is usually present, allowing the base station to cover its immediate area more efficiently, without causing RF interference to distant areas.
Sector antenna downtilt
The coverage area determined by the projection of the radiation pattern onto the ground can be adjusted by changing the downward tilt of the pattern. In some models, this is done mechanically by manually adjusting the tilt of the antenna with an adjustable mounting bracket. In closer sector antennas, the pattern can be electronically tilted using adjustable phase shifters in the feeds to the individual dipole elements. These are adjusted from the ground by remote control circuits, eliminating the need for the technician to climb the antenna tower.
Sector antenna classification
There are two forms of sector antennas, metal plate type and metal wire type. This type of antenna widens the antenna band because it increases the antenna section area. Wire-type sector antennas can use three, four, or five metal wires.
Who manufactures sector antennas?
C&T RF Antennas Inc. manufactures many styles of sector antennas for your choice. Contact us for off-the-shelf outdoor sector antennas or design customizations.
