This presentation provides an introduction about the functions and classification of antennas along with the radiation characteristics of a dipole antenna

1. LECTURE 1
ANTENNAS
ECE6
Parismita A Kashyap

2. HISTORY
 The first antennas were built in 1888 by German
physicist Heinrich Hertz in his pioneering experiments to
prove the existence of electromagnetic waves predicted
by the theory of James Clerk Maxwell.

3. WHAT IS AN ANTENNA

6. CONDITIONS UNDER WHICH RADIATION
OCCURS
 Radiation doesn’t occur when charges move
uniformly over a conductor.
 When electric charges oscillates over a
conductor/changes direction radiation occurs
 Time varying current and accelerating charges
causes radiation

7. BASIC STRUCTURE

10. WHERE USED

11. CLASSIFICATION OF ANTENNAS
1. Based on operating frequency:
 Very low (VLF)
 LF
 MF (e.g Monopole and loop)
 HF (e.g Dipole)
 VHF
 UHF (e.g Yagi-Uda, folded dipole, small dish, helical, slot, UWB)
 SHF (e.g optical band antennas)

12. CLASSIFICATION OF ANTENNAS
2. Based on structure:
 Wire antennas
Dipole antennas

13. CLASSIFICATION OF ANTENNAS
2. Based on structure:
 Wire antennas
Folded Dipole antenna Monopole antenna

14. CLASSIFICATION OF ANTENNAS
2. Based on structure:
 Wire antennas
Loop antennas

15. CLASSIFICATION OF ANTENNAS
2. Based on structure:
 Aperture antennas
Horn antenna
Dish antenna

16. CLASSIFICATION OF ANTENNAS
3. Based on purpose:
 Travelling wave antennas
Rhombic antennas

17. CLASSIFICATION OF ANTENNAS
3. Based on purpose:
 Travelling wave antennas
Inverted-V antennas

18. CLASSIFICATION OF ANTENNAS
3. Based on purpose:
 Broadband antennas
Helical antennas

19. CLASSIFICATION OF ANTENNAS
3. Based on purpose:
 Broadband antennas
Yagi-Uda antennas Folded dipole
antenna

20. CLASSIFICATION OF ANTENNAS

21. CLASSIFICATION OF ANTENNAS

22. ANTENNA FIELD ZONES
•The dividing line “Rule
of Thumb” is
R = 2L2/.
•The near field or
Fresnel zone is r < R
The far field or
Fraunhofer zone is
r > R

23. RADIATION MECHANISM

26. FIELDS FROM OSCILLATING DIPOLE

27. FIELDS FROM A HALF WAVE DIPOLE

28. SIMPLE DIPOLE ANTENNA

29. CURRENT DISTRIBUTION FOR Λ/2 DIPOLE

30. CURRENT DISTRIBUTION FOR DIFFERENT
LENGTHS

31. RADIATION PATTERN OF A DIPOLE ANTENNA

32. MORE

33. RADIATION PATTERN OF HALFWAVE DIPOLE

34. 2D PATTERN OF HALFWAVE DIPOLE

35. FOR DIPOLE AND MONOPOLE

36. CONTINUED….

37. FOR 1.5Λ

38. RADIATION PATTERN FOR LENGTH 1.25Λ

39. PATTERN FOR 1.25Λ

40. PATTERNS FOR DIFFERENT LENGTH