this described types of antenna

2. 3.1 Introduction of Monopole and Dipole
(wire antenna)
The dipole and the monopole are arguably the two
most widely used antennas across the UHF, VHF
and lower-microwave bands. Arrays of dipoles are
commonly used as base-station antennas in land-
mobile systems. The monopole and its variations
are common in portable equipment, such as
cellular telephones, cordless telephones,
automobiles, trains, etc. It has attractive features
such as simple construction, sufficiently
broadband characteristics for voice
communication, small dimensions at high
frequencies.

3. 3.2 . Infinitesimal Dipole
 Length l << l
• Used to represent capacitor-plate (top-hat loaded)
antennas
• Capacitive loading to maintain the uniform
current

4. 3.2 . Infinitesimal Dipole

5. 3.2 . Infinitesimal Dipole

6. 3.2 . Infinitesimal Dipole

7. 3.2 . Infinitesimal Dipole(Power Density and Radiation
Resistance)

8. 3.2 . Infinitesimal Dipole(Power Density and Radiation
Resistance)

9. 3.2 . Infinitesimal Dipole (Far Field (kr >> 1)

10. 3.2 . Infinitesimal Dipole (Directivity)

11. 11
Example 1
Suppose a Hertzian dipole antenna is 1 cm long
and is excited by a 10 mA amplitude current
source at 100 MHz. What is the maximum power
density radiated by this antenna at a 1 km
distance? What is the antenna’s radiation
resistance?

12. Solution to Example 1
8
6
3 10
, 3 .
100 10 1
c x m s
c f m
f x s
 
   
     
2 2 2
2 2 2
max 2 2 2 2 2 2
2 0.010 0.010
120
0.052
32 32 3 1000
o o
I pW
P
r m

  
 
  
l
2 2
2 2 0.01
80 80 8.8
3
rad
R m
 

   
   
   
   
l
We should calculate the wavelength,
The max. power radiated is:
The antenna radiation resistance :

13. 3.3 Small Dipole

14. 3.3 Small Dipole (radiated field)

15. 3.3 Small Dipole (radiated field)

16. 3.5 half wave Dipole

17. 3.5 half wave Dipole

18. Dipole Antennas (Cont’d..)

19. 3D and 2D amplitude patterns for a thin dipole of l=1.25λ
Dipole Antennas (Cont’d..)

20. Summary of Key Antenna Parameters