Presentation2

A SEMINAR PRESENTATION ON PLASMA ANTENNA

Presented by Hari Om Shanker Mishra M.Tech (ECE) Enrollment No.-12302255

Outline of the presentation

1- Introduction2- What is Plasma 3- Plasma antenna 4- Advantages of plasma antenna5- Disadvantages of plasma antenna6- Plasma antenna theory7- Working principle of plasma antenna 8- Application9- Recent development 10- Conclusion11- References

Introduction What is plasma ?

1- Plasma is the fourth state of matter ,the other three are solid, liquid, and gas.

2- A plasma is an ionized gas.

3- A gas becomes a plasma, when the addition of heat or other energy causes a significant number of atoms to release some or all of their electrons.

4- The detached negative electrons are free to move.

5- The atoms are left with positive charge.

6- The electrically charged gas are said to be “ionized”.

7- When enough atoms are ionized to significantly affect the electrical properties of the gas, “it is a plasma.”

8- In short we can say that plasma is made of free electron and positively charged ions.

9- The degree of ionization in plasma –“The rate of ionized particles against the total present particles”.

10- It depends mainly on temperature. And it is calculated by -

KT

uCT

n

n i

n

i exp2

32

Where C=2.4x1021/m3 , ni is the ion concentration - which have lost one electron, nn is the neutral particles concentration, ui is the ionization potential, T is the plasma temperature.

Plasma antenna

1- Plasma antenna employs ionized gas enclosed in a tube (or other enclosure) as the conducting element of an antenna.

2- Plasma, or ionized volume, simply replaces a solid conductors.

3- A highly ionized plasma is a good conductors, therefore plasma Filament can serve as transmission line elements for guiding waves.

4- A ionized volume can take a variety of forms. It can be established in air at atmospheric pressure by using Lasers, high power microwave beams or ultraviolet rays.

5- A plasma might also be generated from a gas filled tube containing a noble gas like Neon or Argon.

6- Using of tube require less energy to excite and maintain the plasma state, because the gas is pure and the pressure of the tube prevents dissipation.

7- The use of a tube required that it must be protected from the environment, which increase the antenna weight and volume, and make the antenna less durables.

8-The following figure shows the some basic structure of plasma antenna…

IONIZED GAS PLASMA ANTENNA PLASMA TUBE ANTENNA

Figure of Ionized gas and Tube Plasma Antenna

Advantages of plasma antenna

1- The length of an ionized filament can be changed rapidly, thereby “retuning” the antenna to a new frequency.

2- The antenna can be “turned off” to make it electrically invisible.

This reduce scattering and eliminating coupling ,interference with other nearby antenna.

3- High gain.

4- Wide bandwidth.

5- Compact and light weight.

6- Maintence free.

7- The design allows for extremely short pulse, important to many forms of digital communication and radar.

8-When a plasma element is not energized it is difficult to detect by radar. Even when it is energized, it is transparent to the transmissions above the plasma frequency.

9- It can operate up to 90 GHz.

Disadvantage of plasma antenna

1-The ionizer increases power consumption. More energy is required to ionize the gases or to make the silicon chips release electrons. Therefore, plasma antennas actually use more power than normal antennas.

2- Plasma volumes must be stable and repeatable. When a gas is ionized, not all 100% of the gas will ionize to become plasma.

With silicon chips, it is reasonable to say that the amount of electrons released by the silicon when heated or charged will vary from time to time.

Thus it is imperative that the volume of plasma generated each time should be the same.

The amount of plasma existing during a transmission or reception should also be the stable and not fluctuate. Only then will the electromagnetic waves transmitted be stable.

Plasma antenna theory

1- Let center-fed dipole plasma antenna with triangular current.2- let plasma dipole antenna oriented along the z-axis. 3- The dielectric constant for the plasma is definedas-

where

j

p

2

1

m

nep

0

2

p is the plasma frequency, and m is the mass of the electron, is the electron velocity ,e is the charge on electron , is the applied frequency in radian per second.

The dipole moment of the plasma antenna is given by-

where a is the cross- section area of the plasma

antenna and d is the length of the plasma antenna.

The total radiated power is-

where is the

wave number. Thus the radiated power depends on the plasma frequency and collision rate.

200

2

2 pj

dEneaP

2

0

22

12p

c

kP rad

2

k

22222

2042

20

48

pprad

Ekd

c

aP

GENERATION OF ELECTRIC AND MAGNETIC FIELD

1- When voltage applied to an antenna, electric field produced.

2- Causes current to flow in antenna.

3- Due to current flow, magnetic field produced.

4- These two fields are emitted from an antenna and propagate through space over very long distances.

How does plasma antenna work ?

1- When supply is given to the tube, the gas inside it gets ionized to plasma.

2- When plasma is highly energized, it behaves as a conductor.

3- Antenna generates a localized concentration of plasma to form a plasma mirror that deflects RF beam launched from a central feed located at focus of mirror.

WORKING PRINICIPLE FIGURE

Reflectors

If the frequency is lower than the plasma frequency ,the

Plasma behaves as reflector and EM wave are attenuated.

Comparison of radiation pattern from plasma (blue) and metal (red).

comparison of radiation patterns from plasma and metal antennas. The plasma antenna shows lower side lobes, especially at wide angles, due to its higher surface resistivity compared to a solid conductor .

Plasma pattern has a better directivity, and the side lobe level is also better in the plasma pattern.

Application

MILLITARY APPLICATIONS-

1-Shipboard/submarine antenna replacements.

2-Unmanned air vehicle sensor antennas.

3- land-based vehicle antennas.

4-Stealth aircraft antenna replacements.

COMMERCIAL APPLICATIONS-

1- Telemetry & broad-band

communications.

2- Ground penetrating radar.

3- Navigation.

4- Weather radar and wind

shear detection.

5- Collision avoidance .

6- High-speed data

communication.

Recent development

The future of high-frequency, high-speed wireless communications could very well be plasma antennas capable of transmitting focused radio waves that would quickly dissipate using conventional antennas.

Thus, plasma antennas might be able to revolutionize not just high-speed wireless communications .

Higher frequencies mean shorter wavelengths and hence smaller antennas. The antenna actually becomes cheaper with the smaller size .

Plasma antenna to be used for next generation Wi-Gig (its version 1.0 was announced in December 2009) that can reach up to 7Gbps bandwidth over frequencies up to 60 GHz. 

Conclusion

 The plasma antenna works according to the same principles and physics laws as the normal antenna, with plasma replacing the metal conductors of the normal antenna.

But because the conducting material used is plasma, it affords some advantages over a normal antenna.

The most notable advantage of the plasma antenna is the fact that it is practically invisible to radar and can release short pulses of signals.

Therefore, the military of US is currently racing to implement the plasma antenna into their existing systems.

References

[1] Kumar V., Mishra M., and Joshi N.K., “study of fluorescent tube as plasma antenna”, Progress In Electromagnetic Research Letters, Vol. 24, 17{26, 2011}

[2] Li Wei, Qiu Jinghui and Suo Ying, “analysis and design of plasma monopole antenna” International Conference on Antenna Theory and Techniques, 6-9 October, 2009, Lviv, Ukraine pp. 200-202.

[3] Gusein-Zade N. G., Minaev I. M., Rukhadze A. A., and Rukhadze K. Z., “Physical Principles of Plasma Antenna Operation” Journal of Communications Technology and Electronics, 2011, Vol. 56, No. 10, pp. 1207–1211.

[4] Kraus J.D., “Antennas for all applications”, second edition, “Tata McGraw-Hill 1988”.

[5] Balanis C.A. “Antenna theory analysis and design” second edition, “John Wiley &sons, Inc 1997”.

Thank you