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# Omni directional antenna

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### Omni directional antenna

1. 1. OMNI-DIRECTIONAL ANTENNA By, PRAVEEN M K I M.TECH(DCN) 9913107002 1/25/2014 1
2. 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. 1/25/2014 2
3. 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. 1/25/2014 3
4. 4. ANTENNA CHARACTERISTICS: (i)Radiation Pattern:  The radiation pattern is often described as "doughnut shaped". 1/25/2014 4
5. 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. 1/25/2014 5
6. 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)** 1/25/2014 6
7. 7. Types of ODA: Whip antenna  Rubber duck antenna  Ground plane antenna  Discone antenna etc…..,  1/25/2014 7
8. 8. How it looks like…??? 1/25/2014 8
9. 9. Used in, Mobile phones  Wi-fi modem’s  Walkie-Takie’s  Cars-(FM antenna)  Wireless Microphones(Mike) etc…,  1/25/2014 9
10. 10. Limitations:  Although their gain should be very high, due to some external factors i.e..,(interference, fading etc..,) their gain should get decreased. 1/25/2014 10
11. 11. 1/25/2014 11