Slot antenna
Encyclopedia
A slot antenna consists of a metal
surface, usually a flat plate, with a hole or slot cut out. When the plate is driven
as an antenna
by a driving frequency, the slot radiates electromagnetic waves in similar way to a dipole antenna
. The shape and size of the slot, as well as the driving frequency, determine the radiation distribution pattern
. Often the radio waves are provided by a waveguide
, and the antenna consists of slots in the waveguide. Slot antennas are often used at UHF and microwave
frequencies instead of line antennas when greater control of the radiation pattern
is required. Slot antennas are widely used in radar
antennas, for the sector antenna
s used for cell phone base stations
, and are often found in standard desktop microwave
sources used for research purposes.
A slot antenna's main advantages are its size, design simplicity, robustness, and convenient adaptation to mass production using PC board technology.
The slot antenna was invented in 1938 by Alan Blumlein
, while working for EMI
. He invented it in order to produce a practical type of antenna for VHF television broadcasting that would have horizontal polarization, an omni-directional horizontal radiation pattern and a narrow vertical radiation pattern.
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
surface, usually a flat plate, with a hole or slot cut out. When the plate is driven
Driven element
In a multielement antenna array , the driven element or active element is the element in the antenna which is electrically connected to the receiver or transmitter. In a transmitting antenna it is driven or excited by the RF current from the transmitter, and is the source of the radio waves...
as an antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
by a driving frequency, the slot radiates electromagnetic waves in similar way to a dipole antenna
Dipole antenna
A dipole antenna is a radio antenna that can be made of a simple wire, with a center-fed driven element. It consists of two metal conductors of rod or wire, oriented parallel and collinear with each other , with a small space between them. The radio frequency voltage is applied to the antenna at...
. The shape and size of the slot, as well as the driving frequency, determine the radiation distribution 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 ....
. Often the radio waves are provided by a waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
, and the antenna consists of slots in the waveguide. Slot antennas are often used at UHF and microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
frequencies instead of line antennas when greater control of the 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 ....
is required. Slot antennas are widely used in radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
antennas, for the sector antenna
Sector antenna
A sector antenna is a type of directional microwave antenna with a sector-shaped radiation pattern. The word "sector" is used in the geometric sense; some portion of the circumference of a circle measured in degrees of arc...
s used for cell phone base stations
Cell site
A cell site is a term used to describe a site where antennas and electronic communications equipment are placed, usually on a radio mast, tower or other high place, to create a cell in a cellular network...
, and are often found in standard desktop microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
sources used for research purposes.
A slot antenna's main advantages are its size, design simplicity, robustness, and convenient adaptation to mass production using PC board technology.
The slot antenna was invented in 1938 by Alan Blumlein
Alan Blumlein
Alan Dower Blumlein was a British electronics engineer, notable for his many inventions in telecommunications, sound recording, stereo, television and radar...
, while working for EMI
EMI
The EMI Group, also known as EMI Music or simply EMI, is a multinational music company headquartered in London, United Kingdom. It is the fourth-largest business group and family of record labels in the recording industry and one of the "big four" record companies. EMI Group also has a major...
. He invented it in order to produce a practical type of antenna for VHF television broadcasting that would have horizontal polarization, an omni-directional horizontal radiation pattern and a narrow vertical radiation pattern.
External links
- Slot Antennas www.antenna-theory.com