plasma antenna
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Plasma Antenna-Fadadu Jaydip(08BEC024)
-Gor Kuldip (08BEC030)
Plasma Antenna
Plasma Antenna
An ordinary matter found by Sir William Crookes
a fourth state of matter, now known as plasma.
Plasmas are conductive assemblies of charged and neutral particles.
Plasmas carry electrical currents and generate magnetic fields.
Types of Plasma are:- Warm Plasma Cold Plasma Cold Plasma is used for antenna applications
Plasma Overview
A plasma can be generated from neutral molecules that are separated into negative electrons and positive ions by an ionization process (e.g., laser heating or spark discharge).
Compositions that may be used to form plasma in a tube include gases of neon, xenon, argon, krypton, hydrogen, helium, and mercury vapor.
The positive ions and neutral particles are much heavier than the electrons, and therefore the electrons can be considered as moving through a continuous stationary fluid of ions.
Generation of Plasma
It employs ionized gas enclosed in a tube as the conducting element of an antenna. . This is a fundamental change from traditional antenna design that generally employs solid metal wires as the conducting element.
The gas is ionized only for the time of transmission or reception.
Plasma Antenna Technology
Plasma antenna - conducting element - ionized gas enclosed in a tube as a of an antenna.
When the Gas is ionized to a plasma state -then it becomes conductive, allowing radio frequency (RF) signals to be transmitted or received
In order for plasma to have significant effect on an electromagnetic wave, the electronic density must be increased by several orders of magnitude.
When the gas is not ionized or a plasma antenna is turned off - it is transparent and allowing other adjacent antennas to transmit or receive without interference.
How Does Plasma Antenna Work?
For antenna applications the plasma must be maintained in precise spatial distributions, such as filaments, columns, or sheets.
The plasma volume can be contained in an enclosure (tube) or suspended in free space.
The tube confines the gas and prevents diffusion.
Generation of Plasma For Antenna
Energizing the plasma can be accomplished with electrodes, fiber optics, microwave signals, lasers, RF heating, or electromagnetic couplers.
The radiation pattern is controlled by parameters such as plasma density, tube shape, and current distribution.
Contd.
A conventional tube-requiring two or more contacts (electrodes) for applying the ionizing potential.
A surface wave can be used to excite the plasma from a single end.
The surface space-charge wave is electro-mechanical in nature.
A time-harmonic axial electric field is applied from one end of the plasma column.
Charges are displaced and restoring electric fields are set up in response to the applied field.
Charge Distribution
Charge Distribution
Plasma As A Reflactor
The reflections actually occur within the plasma, not at an abrupt interface as they do for a metal reflector.
In one approach, a laser beam and optics generate a reflecting surface by using a sequence of line discharges that diffuse together to form a sheet of plasma.
A high quality plasma reflector must have a critical surface that can be consistently reproduced and is stable over the transmission times of interest.
When the plasma is turned off, its decay time will limit how fast the reflecting surface can be moved.
Plasma As A Reflactor
A plasma is an ionised gas which, when sufficiently dense, behaves as a conductor. A plasma antenna generates localised concentrations of plasma to form a plasma mirror which deflects an RF beam launched from a central feed located at the focus of the mirror.
An ionised region, or solid state plasma, that are positioned between closely spaced metalized surfaces which constrain the beam. Then the beam is deflected by the desired geometry of the reflector.
Explanation
Contd.
Figure “Loop antenna“ shows one of the many designs that incorporate closed tubes of gas excited by voltages applied to electrodes.
Ionization of Plasma
Loop antenna
Figure “Returnable Antenna”is reconfigurable in that one or more plasma paths can be excited. Different paths would be used in different frequency bands.
Ionization of Plasma
Figure represent oppositely directed lasers that are fired alternately.
Each time the laser is fired, a pulse train is transmitted. The resonant frequency of the plasma in the tube is the transmit frequency.
Plasma Radiation
Plasma Radiation
Does not interact with RF radiation.
Deionizing the gas antenna will not backscatter radar waves (providing stealth).
Reduces computer signal processing requirements.
Unique Characteristics of Plasma Antenna
Reduced radar cross section provides stealth due to the non-metallic elements.
Changes in the ion density can result in instantaneous changes in bandwidth over wide dynamic ranges.
After the gas is ionized, the plasma antenna has virtually no noise floor.
Unique Characteristics of Plasma Antenna
A single dynamic antenna structure can use time multiplexing so that many RF subsystems can share one antenna resource.
Our plasma antenna can transmit and receive from the same aperture provided the frequencies are widely separated.
Unique Characteristics of Plasma Antenna
Applications Of Plasma Antenna
Microwave CommunicationPlasma Antenna Provide:- -Ease for realignment of long range directional antennas. -Low Cost for the network owner. Directional antennas have been the mainstay of microwave
communications. Fixed directional antennas require manual alignment on installation and realignment in the case drift or relocation of either end of the link. Expensive site visits by service personnel drive up costs for the network owner. Mechanically steered antennas are too costly for most fixed applications. In nomadic scenarios, mechanical steering is deployed to ease realignment of large, long range directional antennas.
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Plasma Antennas Provides:- -Selectable multi-beam -Directional beamforming at another frequency -Powerful dual-band combination provides an efficient and
compact ‘single-antenna’ solution for local WiFi Plasma Antennas’ SelectaBeam SC-750 Series of selectable
multi-beam antennas combine an optional omnidirectional mode operating at one frequency band, with directional beamforming at another frequency. This powerful dual-band combination provides an efficient and compact ‘single-antenna’ solution for local WiFi hot-spots within metropolitan or rural area WiMAX network.
WiFi-WiMAX Local Access Point
Shipboard/submarine antenna replacements.
Unmanned air vehicle sensor antennas.
IFF land-based vehicle antennas.
Stealth aircraft antenna replacements.
Military Applications
Telemetry & broad-band communications.
Ground penetrating radar.
Navigation. High-speed data
communication.
COMMERCIAL APPLICATIONS
Plasma Antennas leads the world in developing low cost plas76 antennas across the band 1 GHz to 300 GHz.
A circular scan can be performed electronically with no moving parts at a higher speed than traditional mechanical antenna structures.
Why Should We Use Plasma Antenna???
Good RF coupling for electrically small antennas
Frequency selectivity Stable and repeatable Efficient Flexibility in length and direction of path High gain Low interference Wide bandwidth Maintenance free Perfect Reflector
Why Should We Use Plasma Antenna???
As soon as the plasma generator is switched off, the plasma returns to a non conductive gas and therefore becomes effectively invisible to radar.
They can be dynamically tuned and reconfigured for frequency, direction, bandwidth, gain and beamwidth, so replacing the need for multiple antennas.
They are resistant to electronic warfare. At satellite frequencies, they exhibit much
less thermal noise and are capable of faster data rates.
Why Should We Use Plasma Antenna???
Ionization and decay times limit scanning.
Plasma volumes must be stable and repeatable.
Ionizer adds weight and volume. Ionizer increases power
consumption. Not durable or flexible.
Disadvantages
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