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WELCOME
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Seminar On
By
Shruti Ranjan Behura
Regd. No.: 0621212042
Dept.: EnTC Engg.
Sem.: 7th
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Contents
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Introduction
Generation of plasma
Plasma antenna system
Containment of plasma
Distribution of charge
Plasma reflector
Ionization of plasma
Advantages
Disadvantages
Technology description
Applications
Conclusion
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INTRODUCTION
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An ionized gas, when sufficiently
dense, behaves as a conductor. A plasma
antenna generates localized 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.
A highly ionized plasma is essentially a
good conductor, and therefore plasma filaments
can serve as transmission line elements for
guiding waves, or antenna surfaces for
radiation.
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GENERATION OF PLASMA
A plasma can be generated from
neutral molecules (like Neon, Argon) that are
separated into negative electrons and positive
ions by an ionization process (e.g., laser heating
or spark discharge).
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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.
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PLASMA ANTENNA SYSTEM
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An antenna system and method for a plurality of plasma
antennas driven by means of an optical driver.
In one embodiment the driver comprises one or more lasers
which may be modulated by one or more electro-optical
modulators to produce a modulated laser signal.
The modulated laser signal may be supplied to the plasma
antenna by optical fibers whereby the photons from the
modulated signal impart momentum to the plasma particles.
The plasma particles, which may include unbound electrons,
oscillate in accord with the modulated laser signal to radiate
electromagnetic energy.
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CONTAINMENT OF PLASMA
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.
Compositions that may be used to
form plasma in a tube include gases
of neon, xenon, argon, krypton,
hydrogen, helium, and mercury vapor.
Plasma Loop
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CONTAINMENT CONTD….
Energizing the plasma can be
accomplished with electrodes, fiber
optics, microwave signals, lasers, RF
heating, or electromagnetic couplers.
The tube confines the gas and
prevents diffusion. The radiation
pattern is controlled by parameters
such as plasma density, tube shape,
and current distribution.
Plasma Loop
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DISTRIBUTION OF CHARGE
A conventional tube has the
disadvantage of requiring two or
more contacts (electrodes) for
applying the ionizing potential.
As an alternative, 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 a one end of the
plasma column. Charges are
displaced and restoring electric
fields are set up in response to
the applied field.
Surfatron tube
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PLASMA REFLECTOR
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.
Plasma reflector
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.
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HOW DOES IT WORK?
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.
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IONIZATION OF PLASMA
Figure “Loop antenna“ shows
two of the many designs that
incorporate closed tubes of gas
excited by voltages applied to
electrodes.
Figure “Returnable Antenna”
is reconfigurable in that one or
more plasma paths can be
excited. Different paths would
be used in different frequency
bands.
Loop antenna
Returnable Antenna
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PLASMA RADIATION
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.
System block diagram
Waveform
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ADVANTAGES
Reduced interference & ringing.
 Change shape to control plasma pattern &
bandwidth.
 Change plasma parameter.
 Good
RF coupling for electrically small
antennas
 Frequency selectivity
 Stable and repeatable
 Efficient
 Flexibility in length and direction of path
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DISADVANTAGES
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.
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TECHNOLOGY DESCRIPTION
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The company has developed theoretical models, conducted
experiments, and built prototypes of plasma antennas in the
laboratory. The company’s plasma antennas include glass
or ceramic tubes containing ionized gas.
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The antennas can be reconfigured dynamically for
frequency, direction, bandwidth, gain, and beam width. That
reconfigurability allows one antenna to do the work of
several conventional antennas.
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A reduction in the number of conventional antennas
decreases clutter and weight on a structure (a
communications tower, an aircraft, a spacecraft, a boat or
ship, etc.). Fewer antennas also will result in less
interference among antennas.
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APPLICATIONS
Defence Applications such as:
Mobile communication
Satellite communication
Radar communication
Domestic Application such as:
TV/Radio Broadcasting.
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SUMMARY
These kinds of antennas could prove
themselves a valuable asset on a battlefield,
where they could be easily kept out of sight,
reduce the number of conventional antennas
and the weight of the structure carrying such
an antenna, prevent signal jamming attempts
through rapid adjustments in the frequency,
direction, bandwidth and other parameters.
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CONCLUSION
The continuing advances in lasers, tubes, solid
state electronics, and signal processing
capabilities, have made many of the simpler
plasma concepts realizable.
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REFERENCES
J. Drummond, Plasma Physics, McGraw-Hill.
 U. Inan and A. Inan, Electromagnetic Waves,
Prentice-Hall.
 http://www.asiplasma.com
 http://wwwrsphysse.anu.edu.au/~ggb112/ind
ex.html#
 http://wwwrsphysse.anu.edu.au/~ggb112/ind
ex.html#
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THANK YOU
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