Plasma antenna
Encyclopedia
A plasma antenna is a type of radio antenna
currently in development in which plasma
is used instead of the metal elements of a traditional antenna. A plasma antenna can be used for both transmission
and reception
. Although plasma antennas have only become practical in recent years, the idea is not new; a patent for an antenna using the concept was granted to J Hettinger in 1919.
Early practical examples of the technology used discharge tubes
to contain the plasma and are referred to as ionized gas plasma antennas. Ionized gas plasma antennas can be turned on and off and are good for stealth and resistance to electronic warfare and cyber attacks. The higher frequency ionized gas plasma antennas can transmit and receive through lower frequency ionized gas plasma antennas. Ionized gas plasma antennas can be nested such that the higher frequency plasma antennas are placed inside lower frequency plasma antennas. Higher frequency ionized gas plasma antenna arrays can transmit and receive through lower frequency ionized gas plasma antenna arrays. This means that the ionized gas plasma antennas can be co-located and ionized gas plasma antenna arrays can be stacked. Ionized gas plasma antennas can eliminate or reduce co-site interference. Smart ionized gas plasma antennas use plasma physics to shape and steer the antenna beams without the need of phased arrays. Satellite signals can be steered and/or focused in the reflective or refractive modes using banks of plasma tubes making unique ionized gas satellite plasma antennas. The thermal noise of ionized gas plasma antennas is less than in the corresponding metal antennas at the higher frequencies. Solid state
plasma antennas (also known as plasma silicon antennas) with steerable directional
functionality that can be manufactured using standard silicon chip fabrication techniques are now also in development. Plasma silicon antennas are candidates for use in WiGig
(the planned enhancement to Wi-Fi
), and have other potential applications, for example in reducing the cost of vehicle-mounted radar
collision avoidance systems.
to create a plasma. Unlike gasses, plasmas have very high electrical conductivity so it is possible for radio frequency
signals to travel through them so that they act as a driven element
(such as a dipole antenna
) to radiate radio waves, or to receive them. Alternatively the plasma can be used as a reflector
or a lens
to guide and focus radio waves from another source.
Solid-state antennas differ in that the plasma is created from electron
s generated by activating thousands of diode
s on a silicon chip.
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...
currently in development in which plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
is used instead of the metal elements of a traditional antenna. A plasma antenna can be used for both transmission
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
and reception
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
. Although plasma antennas have only become practical in recent years, the idea is not new; a patent for an antenna using the concept was granted to J Hettinger in 1919.
Early practical examples of the technology used discharge tubes
Gas-filled tube
A gas-filled tube, also known as a discharge tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Although the envelope is typically glass, power tubes often use ceramics, and military tubes often use glass-lined metal...
to contain the plasma and are referred to as ionized gas plasma antennas. Ionized gas plasma antennas can be turned on and off and are good for stealth and resistance to electronic warfare and cyber attacks. The higher frequency ionized gas plasma antennas can transmit and receive through lower frequency ionized gas plasma antennas. Ionized gas plasma antennas can be nested such that the higher frequency plasma antennas are placed inside lower frequency plasma antennas. Higher frequency ionized gas plasma antenna arrays can transmit and receive through lower frequency ionized gas plasma antenna arrays. This means that the ionized gas plasma antennas can be co-located and ionized gas plasma antenna arrays can be stacked. Ionized gas plasma antennas can eliminate or reduce co-site interference. Smart ionized gas plasma antennas use plasma physics to shape and steer the antenna beams without the need of phased arrays. Satellite signals can be steered and/or focused in the reflective or refractive modes using banks of plasma tubes making unique ionized gas satellite plasma antennas. The thermal noise of ionized gas plasma antennas is less than in the corresponding metal antennas at the higher frequencies. Solid state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...
plasma antennas (also known as plasma silicon antennas) with steerable directional
Directional antenna
A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....
functionality that can be manufactured using standard silicon chip fabrication techniques are now also in development. Plasma silicon antennas are candidates for use in WiGig
Wireless Gigabit Alliance
The Wireless Gigabit Alliance is an organization promoting the adoption of multi-gigabit speed wireless communications technology operating over the unlicensed 60 GHz frequency band....
(the planned enhancement to Wi-Fi
Wi-Fi
Wi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
), and have other potential applications, for example in reducing the cost of vehicle-mounted 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...
collision avoidance systems.
Operation
In an ionized gas plasma antenna, a gas is ionizedIonization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
to create a plasma. Unlike gasses, plasmas have very high electrical conductivity so it is possible for radio frequency
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
signals to travel through them so that they act as a driven element
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...
(such as 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...
) to radiate radio waves, or to receive them. Alternatively the plasma can be used as a reflector
Reflector (antenna)
An antenna reflector is a device that reflects electromagnetic waves.It is often a part of an antenna assembly.The most common reflector types are...
or a lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
to guide and focus radio waves from another source.
Solid-state antennas differ in that the plasma is created from electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s generated by activating thousands of diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
s on a silicon chip.
Advantages
Plasma antennas possess a number of advantages over metal antennas, including:- As soon as the plasma generator is switched off, the plasma returns to a non conductive gasGasGas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
and therefore becomes effectively invisible to radarRadarRadar 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...
. - They can be dynamically tuned and reconfigured for frequencyFrequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, direction, bandwidth, gainGainIn electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...
and beamwidthBeamwidthIn telecommunication, the term beamwidth has the following meanings:1. In the radio regime, of an antenna pattern, the angle between the half-power points of the main lobe, when referenced to the peak effective radiated power of the main lobe....
, so replacing the need for multiple antennas. - They are resistant to electronic warfareElectronic warfareElectronic warfare refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum, attack an enemy, or impede enemy assaults via the spectrum. The purpose of electronic warfare is to deny the opponent the advantage of, and ensure friendly...
. - At satellite frequencies, they exhibit much less thermal noiseJohnson–Nyquist noiseJohnson–Nyquist noise is the electronic noise generated by the thermal agitation of the charge carriers inside an electrical conductor at equilibrium, which happens regardless of any applied voltage...
and are capable of faster data rates.