1. ADVANCED COMPUTER NETWORKS
ANTENNA’S
Presented By
SANKEPALLY VIDYA SAGAR
SAI NAVEEN SESHAM
SHASHIKANT LAKUMA
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2. OVERVIEW INTRODUCTION TYPES PARAMETERS MODELS CONCLUSION
QUESTIONS AND ANSWERS
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3. INTRODUCTION
The origin of the word antenna relative to wireless apparatus is attributed to Guglielmo Marconi. Marconi's use of the word antenna (Italian for pole) would become a popular term for what today is uniformly known as the antenna .
Antenna’s play a primary role in wireless network.
An antenna is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves.
Antennas convert radio frequency electrical currents into electromagnetic waves and vice versa.
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4. PHYSICAL DESIGN
Physically, an antenna is an arrangement of conductors that generate a radiating electromagnetic field in response to an applied alternating voltage and the associated alternating electric current, or can be placed in an electromagnetic field so that the field will induce an alternating current in the antenna and a voltage between its terminals.
Antennas usually work in air or outer space, it can also be operated under water or even through soil and rock at certain frequencies for short distances
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5. A building rooftop supporting numerous dish and sectored mobile telecommunications antennas
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6. TYPES OF ANTENNAS There are two fundamental types of antennas :
Omni-directional and Directional.
A omni-directional antenna (such as a vertical rod) is an antenna system which radiates power uniformly in one plane with a directive pattern shape in a perpendicular plane.
A directional 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.
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7. Yagi-Uda Antenna
By adding additional conducting rods or coils (called elements) and varying their length, spacing, and orientation ,an antenna with these specific desired properties can be created, such as a Yagi-Uda Antenna
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8. CUTAIN ANTENNA
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9. ANTENNA’S
Rooftop television Antenna.
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10. ANTENNA PARAMETERS Gain. Radiation Pattern. Efficiency. Bandwidth.
Resonant Frequency.
Gain.
Radiation Pattern.
Efficiency.
Bandwidth.
Polarization.
Impedance.
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11. TRANSMISSION AND RECEPTION
Antennas used for transmission have a maximum power rating, beyond which heating, arcing or sparking may occur in the components, which may cause them to be damaged or destroyed.
Antennas designed specifically for reception might be optimized for noise rejection capabilities.
All of the antenna parameters are expressed in terms of a transmission antenna, but are identically applicable to a receiving antenna .
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12. ANTENNA MODELS Isotropic radiator. Dipole antenna.
Random wire antenna.
Horn antenna.
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13. ANTENNA MODELS
The isotropic radiator is a purely theoretical antenna that radiates equally in all directions.
The dipole antenna is simply two wires pointed in opposite directions arranged either horizontally or vertically, with one end of each wire connected to the radio and the other end hanging free in space.
The random wire antenna is simply a very long wire with one end connected to the radio and the other in free space, arranged in any way most convenient for the space available.
The Horn is used where high gain is needed, the wavelength is short and space is not an issue.
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14. AFFECT ON GROUND
At frequencies used in antennas, the ground behaves mainly as a dielectric.
The conductivity of ground at these frequencies is negligible.
When an electromagnetic wave arrives at the surface of an object, two waves are created: one enters the dielectric and the other is reflected.
If the object is a conductor, the transmitted wave is negligible and the reflected wave has almost the same amplitude as the incident one.
Most of the electromagnetic waves emitted by an antenna to the ground below the antenna at moderate (say < 60°) angles of incidence enter the earth and are absorbed .
When the angle of incidence is near 90° (grazing incidence) almost all the wave is reflected.
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15. Antenna’s Behavior On Ground
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16. The vertical component of the current reflects without changing sign
The vertical component of the current reflects without changing sign. The horizontal component reverses sign at reflection
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17. CONCLUSION ANY MOBLIE NETWORK CANT BE IMAGINED WITHOUT ANTENNA.
Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless LAN, radar, and space exploration .
ANY MOBLIE NETWORK CANT BE IMAGINED WITHOUT ANTENNA.
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18. QUESTIONS
Q1. Why did you choose titans mysterious radio wave for explaining the concept of antennas?
Q2. The formula mentioned in the conclusion. What significance it has and why/where it is used?
Q3. How do antennas radiate. Could you explain in detail?
Q4.What is the size of antenna and does size of the antenna has effects on other factors?
Q5.How antenna’s parameters influence the design of antennas?
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19. QUESTION 1
Q1. The formula mentioned in the conclusion. What significance it has and why/where it is used?
The simple formula, 〈Pr〉=(E0^2 /η)(λ^2/8π), for the received power of an antenna with a matched load in an over-moded cavity actually holds for an antenna of any shape and size.
Where ,η =The radiation efficiency,
E0=is the electrical field radiated by the antenna
λ=Wave Length.
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20. QUESTIONS 2 Q2. How do antennas radiate. Could you explain in detail?
Ans. The radiation of an antenna describes the relative strength of the radiated field in various directions from the antenna, at a fixed or constant distance. The radiation pattern is a "reception pattern" as well, since it also describes the receiving properties of the antenna. The radiation pattern is three-dimensional . In order to know how an antenna radiates, let us first consider how radiation occurs.
A conducting wire radiates mainly because of time-varying current or an acceleration (ordeceleration) of charge. If there is no motion of charges in a wire, no radiation takes place, since no flow of current occurs.
Radiation will not occur even if charges are moving with uniform velocity along a straight wire. However, charges moving with uniform velocity along a curved or bent wire will produce radiation.
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21. QUESTION 3
Q3.What is the size of antenna and does size of the antenna has effects on other factors?
Unfortunately, there is an inverserelationship between antenna gain and antenna beamwidth. Additionally, there is a proportional relationship between antenna gain and the antenna size.
Antenna Size = Gain ^2 / 4.
The conclusion, therefore, would be that if we increase the antenna size by a factor of two in one plane, we would decrease the beamwidth in that plane by a factor of two and increase the antenna gain by 3 dB.
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22. QUESTION 4
Q4.How antenna’s parameters influence the design of antennas?
Ans.YES
An antenna with a low gain emits radiation in all directions equally, whereas a high-gain antenna will preferentially radiate in particular directions.
For the ideal isotropic antenna, it would be a sphere. For a typical dipole, this would be a toroid
Radiation in an antenna is caused by radiation resistance which can only be measured as part of total resistance including loss resistance. Loss resistance usually results in heat generation rather than radiation, and reduces efficiency.
The bandwidth of an antenna may be increased by several techniques, including using thicker wires, replacing wires with cages to simulate a thicker wire, tapering antenna components (like in a feed horn), and combining multiple antennas into a single assembly .
Polarization:It has nothing in common with antenna directionality terms: "horizontal", "vertical" and "circular". Thus, a simple straight wire antenna will have one polarization when mounted vertically, and a different polarization when mounted horizontally.
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23. ANY QUESTIONS
???
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24. THANK YOU
Have a gr8 day
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