A type of aerial, widely used with television and VHF radio receivers, consisting of two parallel dipoles connected together at their outer ends and fed at the center of one of them. The length is usually half the operating wavelength.

1. FOLDED
DIPOLE
ANTENNA
PRESENTED BY:
NAVIN MANDAL
(700415)
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2. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
CONTENT
 Introduction
 Folded Dipole Basis
 Types Of Folded Dipole
 Design
 Properties
 Radiation Pattern
 Polar Diagram
 Advantage
 Application
 Reference
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3. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
INTRODUCTION
 dipole antenna, with the ends
folded back, and connected to
each other
 width ‘d’ of the folded dipole is
much smaller than the length ‘L’
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0003
Fig. Folded Dipole

4. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
FOLDED DIPOLE ANTENNA BASIC
 Basic Format is
shown in fig
 consists of a basic
dipole with an added
conductor
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03004
Fig. Folded Dipole Antenna Basis

5. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
TYPES OF FOLDED DIPOLE:
1. Unequal conductor
folded dipoles
2. Multi-conductor
folded dipoles
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Fig. Folded Dipole

6. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
1.Unequal Conductor Folded
Dipoles
 varying the effective
diameter of the two
conductors:
top and bottom,
different ratios can be
obtained.
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Fig. Unequal Conductor
Folded Dipole

7. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
The impedance step up ratio provided
by the folded dipole is:
Where,
 d1 = conductor diameter for
the feed arm of the dipole.
 d2 = conductor diameter for
the non-feed arm of the dipole
 s =distance between the
conductors
 r is the step up ratio
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Impedance
𝑟 = 1 +
𝑙𝑜𝑔
2𝑆
𝑑1
𝑙𝑜𝑔
2𝑆
𝑑2
2

8. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
2.Multi-conductor folded
dipoles
 folded dipole antenna often
implies the use of one
extra conductor
 concept can be extended
further by adding
additional 'folds' or
conductors
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Fig. Multi-Conductor Folded
Dipole

9. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
Impedance of Multi-conductor
folded dipoles
 special case where all the conductors have
the same diameter
then the impedance is increased by a
factor of three squared, i.e. 9.
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10. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
DESIGN
 The Length of folded
dipole
* La = 145 / freq (
MHz )
 Length of coil
* for 75 ohm cable : Lb
= La x 0.8
* for 50 ohm cable: Lb =
La x 0.66
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Fig. Folded Dipole Design

11. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
PROPERTIES OF FOLDED
DIPOLE
Impedance properties
Ease of construction
Structural rigidity
Wider bandwidth than λ/2 dipole
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12. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
Radiation Pattern
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Fig. Radiation Pattern

13. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
Radiation Pattern
 reflects the 'sensitivity' of the antenna in
different directions
 knowledge of this allows the antenna to be
orientated in the optimum direction to ensure
the required performance
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14. Fig: Antenna polar
diagram concept
Polar Diagram
Plot that indicates the
magnitude of the
response in any direction
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15. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
ADVANTAGES:
 Increase in impedance:
 Wide bandwidth:
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16. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
APPLICATION
folded dipoles find more uses
when a dipole is incorporated
domestic television
 VHF FM broadcast antennas
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17. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
Reference
 John D Kraus, Ronald J Marhrfka & Ahmed S
Khan Ch.6-24
 Martin E. Meserve - K7MEM - Folded Dipole
Design.html
 Dipole Radiation Patterns _ Antenna Polar
Diagram _ Tutorial.html
 Dipole antenna/Folded Dipole Antenna _ Folded
Dipole Aerial _ Tutorial.html
visited on: August 2,2016
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18. PRESENTATION ON:
FOLDED DIPOLE ANTENNA
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