Null fill in
radio engineering is used in
radio
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
antenna systems which are located on
mountain
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...
s or tall
tower
A tower is a tall Nonbuilding structure, structure, taller than it is wide, often by a significant factor. Towers are distinguished from guyed mast, masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting ...
s, to prevent too much of the
signal
A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology.
In ...
from overshooting the nearest part of intended coverage area.
Phasing is used between antenna elements to take
power away from the
main lobe
In a antenna (electronics), radio antennas, the main lobe or main beam is the region of the radiation pattern containing the highest Power (physics), power or exhibiting the greatest field strength.
The radiation pattern of most antennas shows ...
and electrically direct more of it at a more downward angle in the
vertical plane
In astronomy, geography, and related sciences and contexts, a '' direction'' or '' plane'' passing by a given point is said to be vertical if it contains the local gravity direction at that point.
Conversely, a direction, plane, or surface is ...
. This requires a
phased array
In antenna (radio), antenna theory, a phased array usually means an electronically scanned array, a computer-controlled Antenna array, array of antennas which creates a radio beam, beam of radio waves that can be electronically steered to point ...
. Changing the relative power supplied to each element also changes the
radiation pattern
In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: " ...
in this manner, and often both methods are used in combination.
See also
*
Null (radio)
In radio electronics, a null is a direction in an antenna's radiation pattern where the antenna radiates almost no radio waves, so the far field signal strength is a local minimum. Nulls occur because different parts of an antenna radiate radio ...
*
Beam tilt
References
* "Analysis of Antenna Null-fill and Broadcast Coverage." Myron D. Fanton. ''ERI Technical Series'', vol. 6, April 200
* "The Tide is Turning." Charles Rhodes
* "A Study on Null-Fill Array Antenna for Service Coverage Expansion in PCS Band" Youngseok Ko
Antennas (radio)
Broadcast engineering
{{broadcast-stub