plasma.aman.pdf

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International Journal of Engineering Trends and Technology (IJETT) Volume 15 Number 6 Sep 2014

ISSN: 2231-5381 http://www.ijettjournal.org Page 275

Plasma Antenna

Chintan Patel11

, Nadeem Masani12

, Tushar Parekh13

1Undergraduate Student, Electronics And Telecommunications Engineering Department,

Dwarkadas J. Sanghvi College Of Engineering, Mumbai, India.

Abstract- Radio antennas currently in implementation use

metallic conductor as guiding medium for electromagneticradiations. Plasma antennas uses ionized medium. In this paperwe have discussed the basic theory, operation of the plasmaantenna. We have also given the features, advantages andapplications for the same.

Keywords-Plasma, antenna, ionized gas.

I. Introduction

Plasma antenna is not a new concept, its patent dates back to

1919 which was awarded to J. Hettinger. Plasma antenna

uses ionized gas for guiding electromagnetic waves. Itreplaces a solid conductor which is widely used in the current

radio antennas. Highly ionized plasma is a good conductor

and thus it is used as transmission line for guiding waves.

Neutral molecules can be separated into positive ions and

negative ions using ionization process which helps in

generation of plasma. Electrons are much lighter than

positive ions and neutral ions. Thus electrons are consideredto be moving through stationary fluid of ions and neutrals

with some friction. The propagation characteristics of

electromagnetic (EM) waves in a uniform ionized medium

can be inferred from the equation of motion of a single

typical electron. Such a medium is called cold plasma.[1]

The positive and negative charges in neutral plasma are

uniformly distributed. Hence they appear electrically neutralat a macroscopic scale. Disturbance causes displacement of

charges which gives rise to plasma oscillations. The

displacement of charges sets up an electric field that restores

them to the equilibrium position. Opposite electric field issetup when inertia carries the charges back to their neutral

positions. Unless cold plasma has drift velocity or is finite

and has normal modes that arise from boundary conditions,

in this plasma oscillations dont generally propagate.

In warm plasma the electron thermal velocity cannot be

ignored, but non-relativistic mechanics still apply. The spatialvariations in temperature and density over a wavelength drive

the particle currents, along with the electric field of the EM

wave passing through. Generally, for antenna applications,

cold plasma can be assumed[1].

Fig 1: Plasma antenna.

II. Working

In plasma antenna, ionized gas is being enclosed in the tube

and the gas acts as the conducting material of the antenna.

When this gas is ionized to a plasma state it becomes

conductive replacing the metals which were used in

traditional antenna. The plasma antenna generates localizedconcentrations of plasma to form a plasma mirror whichdeflects a Radio Frequency (RF) beam. The plasma can befreely moved to the desired geometry of the reflector by

plasma diode which enables the beam to be steered quickly

without the need for mechanical motion. [2]When the gas is

not ionized, it allows other antennas to transmit and receive

without any interference which is a very useful feature.

III.

Plasma Reflectors

Plasma behaves as a reflector if the frequency is lower than

the plasma frequency. The reflection occurs at a criticalsurface inside of the plasma. The interesting of this is the

rapid inertia-less two dimensional scanning, frequency

selectivity and potential wideband frequency performance. [3]

Plasma reflectors can be created using laser and optics usinga sequence of line discharges forming a sheet of plasma.


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Fig 2: Plasma reflector using Laser.

Fig 3: Plasma Antenna.

IV.

Features

Ringing effect which was a problem associated with a regular

antenna is due to the traditional metal elements which

reduces its capabilities in high frequency short pulse

transmission. But in plasma antenna the antenna gets

deionized by sending a pulse and thus the problem of ringingeffect is overcome. Another feature of plasma antenna is that

it can easily communicate signals in very short pulses and

also it has the ability to focus a single beam. This feature is

useful in areas of digital communication and radar.

V. Applications

Plasma antennas find its applications in variety of fields due

its unique properties, characteristics and advantages over

traditional metallic antennas.

i) Military applications: Invisibility to radar means that

signals sent by plasma antennas are very difficult to be

detected by any outsider and as military needs to send and

receive top secret information without any outside

interception plasma antennas have qualities and potential that

can be used to develop and produce equipments in militaryapplications within foreseeable future

ii) Faster internet: Plasma antennas can provide a faster rate

of data transmission and hence can be used to provide high

speed internet like Wi-Gig (Wireless Gigabit Alliance) whichis faster than Wi-Fi.

iii) Public safety networks: Public safety networks like

CCTVs are used to prevent crimes, track down criminals and

also may be accepted as video evidence in court. If these

devices are tampered or damaged by criminals then it is

possible to for a handler from safety department to diverge or

reroute the traffic using plasma antennas.

iv) Radio and television broadcasting: Signal strength of

signals emitted by plasma antennas is relatively stronger than

traditionally used normal metal antennas hence it lasts longer

without damping and being extinguished hence broadcastingcompanies may require less relay stations and repeaters to

relay signals to further areas and hence it may bring down

cost of the broadcasting system for service provider

companies.

v) Space communications: Plasma antennas are relatively

lighter than normal antennas and hence can used as

communication devices in spacecrafts like jet planes,commercial planes, even in space shuttles and also in

unmanned air vehicle sensor antennas.

Plasma antennas can also be used in various other

applications like on ships and submarines for stealth to

complete the mission of its crew and also for fishing ships tolocate position of fish in deep sea, detection and tracking of

ballistic missiles, vehicle collision avoidance system etc.

Plasma antennas may well be the future of high-frequency,high-speed wireless communications and the good news is

that plasma antennas will be on-the-shelf maybe within next

couple of years.

VI.

Advantages

The plasma antenna has many advantages over current

conventional antennas which make them suitable for military

and commercial use.

i) Invisible to Radar: Plasma antennas are invisible to

antennas. When the plasma antennas are inactive the radarswill find it difficult to find the antennas. Also when the

antennas are active the radars will have to look for antennasin the plasma frequency, they will be invisible to signals


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above plasma frequency. Hence these signals will be

invisible to detectors other than the intended receivers. This

advantage of plasma antennas make them suitable for

military use.

ii) No Ringing Effect: There is no ringing effect in plasma

antenna as it allows extremely short pulses, which a metal

conductor doesnt allow. When there is sudden change in

input a burst of electricity flow through the metal conductor

for a short time, this is ringing effect. This wastes energyand produces unwanted electromagnetic waves.

iii) More efficient: Plasma antennas can be designed smaller,

lighter and more efficient than the traditional antennas.

Plasma antennas are made more portable by replacing metalconductors with semi-conductor chips or gases.

iv) Dynamically reconfigurable: The gain, frequency,

polarization, power, etc. of the plasma antenna can be

changed by the handler of the antenna. A single plasma

antenna can do work of multiple normal antennas thus

reducing the space and cost required for operation.

v) Fast Transmission: By using plasma semiconductor

antenna the electromagnetic waves produced can be focused

to form a beam which travels faster than wave when certaindiodes are activated

.

VII.Disadvantages:

Use of plasma makes the design of antenna complex. It has

other disadvantages too.

i)

Cannot Penetrate Walls: The semi-conductor plasma

antenna developed by the inventors was limited to highfrequency hence their use also gets limited. Also the signal

from these antennas couldnt penetrate the walls. This can

resolved by using reflectors to make waves reach thedestination.

ii) More Power: More power is used to ionize the gas,

hence ionizer increases power consumption of the antenna.

iii) Stable and repeatable plasma volumes: Not all of the

gas is ionized to become plasma, some parts remainunionized. Thus the volume of the plasma formed during

each time should be same to generate stable electromagnetic

waves. This can be achieved by keeping the current flowing

through it constant, which will excite the same amount ofparticles.

VIII. Conclusion

The principle behind the working of the plasma antenna is

same as the normal conventional antennas. Only the solidmetal conductor is replaced with the plasma. This plasma

gives it many advantages over the current antennas. It is more

efficient, fast and also can be manufactured cheaply. There

might be some disadvantages associated with plasma

antennas but those can be overcome. It will take some timefor plasma antennas to be commercially available, but it will

change the landscape of antennas when it is available for use.

Reference[1]. D.C. Jenn, Plasma Antennas: Survey of Techniques and the

Current State of the Art, September 29, 2003

[2]. http://www.authorstream.com/Presentation/mohantysubhrajit-1541722-plasma-antenna/

[3].

https://www.kth.se/polopoly_fs/1.254028!/Menu/general/column-

content/attachment/report06.pdf

[4].Ritika Nahar, Shaifali Tiwari, Garima Tiwari, Plasma Antenna

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