These Slides are useful to know about an Omni-directional antenna.......

1. OMNI-DIRECTIONAL
ANTENNA
By,
PRAVEEN M K
I M.TECH(DCN)
9913107002
1/25/2014
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2. WHY…….????

Directionality:
◦ Omni (360º coverage) directional
◦ Directional (limited range of coverage)
Compatibility
Should not require any alignment during the
fixation.
Light weight
Easy implementation
Low power consumption
Low cost
Easily replaceable

Gain:
Gain should be more.
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3. ODA:

An Omni-Directional Antenna(ODA) is an
antenna which radiates radio wave power
uniformly in all directions in one plane, with
the radiated power decreasing with
elevation angle above or below the plane,
dropping to zero on the antenna's axis.
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4. ANTENNA
CHARACTERISTICS:
(i)Radiation Pattern:
 The radiation pattern is often
described as "doughnut shaped".
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5. Contd….,
In this case, along the z-axis, which would correspond to
the radiation directly overhead the antenna, there is very
little power transmitted. In the x-y plane (perpendicular to
the z-axis), the radiation is maximum.
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6. (ii)Gain:
Antenna gain is a measure for antennas efficiency.
 Gain is the ratio of the maximum radiation in a
given direction to that of a reference antenna for
equal input power.
 Generally the reference antenna is an isotropic
antenna.
 Gain is measured generally in “decibels above
isotropic (dBi)” or “decibels above a dipole (dBd).
dBi = dBd + 2.15

**(Gain is mainly depends on the mechanical size
of an antenna)**
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7. Types of ODA:
Whip antenna
 Rubber duck antenna
 Ground plane antenna
 Discone antenna etc…..,

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8. How it looks like…???
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9. Used in,
Mobile phones
 Wi-fi modem’s
 Walkie-Takie’s
 Cars-(FM antenna)
 Wireless Microphones(Mike) etc…,

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10. Limitations:

Although their gain should be very high, due
to some external factors i.e..,(interference,
fading etc..,) their gain should get decreased.
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