Beam tilt
Encyclopedia
Beam tilt is used in radio
to aim the main lobe
of the vertical plane
radiation pattern
of an antenna below (or above) the horizontal plane
.
The simplest way is mechanical beam tilt, where the antenna is physically mounted in such a manner as to lower the angle of the signal on one side. However, this also raises it on the other side, making it useful in only very limited situations.
More common is electrical beam tilt, where the phasing between antenna elements is tweaked to make the signal go down (usually) in all directions. This is extremely useful when the antenna is at a very high point, and the edge of the signal is likely to miss the target (broadcast audience, cellphone users, etc.) entirely.
With electrical tilting, front and back lobes tilt in same direction : for example, an electrical downtilt will make both front lobe and back lobe tilt down. This is the property used in the above example where the signal is pointed down in all directions. On the contrary, mechanical downtilting will make the front lobe tilt down and the back lobe tilt up. In almost all practical cases, antennas are only tilted down - though tilting up is technically possible.
A vertical antenna being less visible than a mechanically tilted one, the use of purely electrical tilt with no mechanical tilt is an attractive choice for aesthetic reasons which are very important for operators seeking acceptance of integrated antennas in visible locations.
In GSM and UMTS cellular networks, mechanical tilt is almost always fixed whereas electrical tilt can be controlled using remote actuators and position sensors, thus reducing operating expenses. Remote electrical tilt is abbreviated as RET and it is part of the Antenna Interface Standards Group's open specification for the control interface of antenna devices.
Occasionally, the mechanical and electrical tilt will be used together for odd situations, in order to create greater beam tilt in one direction than the other, mainly to accommodate unusual terrain
. Along with null fill
, beam tilt is the essential parameter controlling the focus of radio
communication
s, and together they can create almost infinite combinations of 3-D radiation pattern
s for any situation.
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
to aim the main lobe
Side lobe
In antenna engineering, side lobes or sidelobes are the lobes of the far field radiation pattern that are not the main lobe....
of the vertical plane
Vertical plane
Vertical plane is used in radio to plot an antenna's relative field strength perpendicular to the ground on a polar graph....
radiation pattern
Radiation pattern
In the field of antenna design the term radiation pattern most commonly refers to the directional dependence of the strength of the radio waves from the antenna or other source ....
of an antenna below (or above) the horizontal plane
Horizontal plane
In geometry, physics, astronomy, geography, and related sciences, a plane is said to be horizontal at a given point if it is perpendicular to the gradient of the gravity field at that point— in other words, if apparent gravity makes a plumb bob hang perpendicular to the plane at that point.In...
.
The simplest way is mechanical beam tilt, where the antenna is physically mounted in such a manner as to lower the angle of the signal on one side. However, this also raises it on the other side, making it useful in only very limited situations.
More common is electrical beam tilt, where the phasing between antenna elements is tweaked to make the signal go down (usually) in all directions. This is extremely useful when the antenna is at a very high point, and the edge of the signal is likely to miss the target (broadcast audience, cellphone users, etc.) entirely.
With electrical tilting, front and back lobes tilt in same direction : for example, an electrical downtilt will make both front lobe and back lobe tilt down. This is the property used in the above example where the signal is pointed down in all directions. On the contrary, mechanical downtilting will make the front lobe tilt down and the back lobe tilt up. In almost all practical cases, antennas are only tilted down - though tilting up is technically possible.
A vertical antenna being less visible than a mechanically tilted one, the use of purely electrical tilt with no mechanical tilt is an attractive choice for aesthetic reasons which are very important for operators seeking acceptance of integrated antennas in visible locations.
In GSM and UMTS cellular networks, mechanical tilt is almost always fixed whereas electrical tilt can be controlled using remote actuators and position sensors, thus reducing operating expenses. Remote electrical tilt is abbreviated as RET and it is part of the Antenna Interface Standards Group's open specification for the control interface of antenna devices.
Occasionally, the mechanical and electrical tilt will be used together for odd situations, in order to create greater beam tilt in one direction than the other, mainly to accommodate unusual terrain
Terrain
Terrain, or land relief, is the vertical and horizontal dimension of land surface. When relief is described underwater, the term bathymetry is used...
. Along with null fill
Null fill
Null fill is used in radio antenna systems which are located on mountains or tall towers, to prevent too much of the signal from overshooting the nearest part of intended coverage area. Phasing is used between antenna elements to take power away from the main lobe and electrically direct more of...
, beam tilt is the essential parameter controlling the focus of radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
communication
Communication
Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...
s, and together they can create almost infinite combinations of 3-D radiation pattern
Radiation pattern
In the field of antenna design the term radiation pattern most commonly refers to the directional dependence of the strength of the radio waves from the antenna or other source ....
s for any situation.