ANTENNAS AND WAVE PROPAGATION Question Bank

Anna University

ANTENNAS AND WAVE PROPAGATION

QUESTION BANK


SUB. CODE/ NAME: EC 2353/ANTENNAS AND WAVE PROPAGATION BRANCH : ECE

YEAR : III

SEM : VI


UNIT I

ELECTROMAGNETIC RADIATION AND ANTENNA FUNDAMENTALS


PART- A (2 MARK)

1. Define an antenna.

2. What is meant by radiation pattern?

3. Define Radiation intensity?

4. Define Beam efficiency?

5. Define Directivity?

6. What are the different types of aperture?

7. Define different types of aperture?

8. Define Aperture efficiency?

9. What is meant by effective height?

10. What are the field zones?

11. What is meant by Polarization?

12. What is meant by front to back ratio?

13. Define antenna efficiency?

14. What is radiation resistance?

15. What is meant by antenna beam width?

16. What is meant by reciprocity Theorem?

17. What is meant by isotropic radiator?

18. Define gain.

19. Define self impedance.

20. Define mutual impedance.

PART– B (16 MARK)

1. Explain the retarded vector potential in detail. (16 M)

2. Derive an expression for the power radiated by the current element and calculate the radiation resistance. (16 M)

3. Derive an expression for the far field component of a half wave dipole of an antenna. (16M)

4. a) Derive the total power radiated by half wave dipole. (8 M)

b) Show that the radiation resistance of a half wave dipole is 80?2 (dl/?)2Ohms. (8 M)

5. Explain the reciprocity theorem in detail. (16 M)

6. Derive an expression for the electric field and magnetic field due to a current element at a distance point in free space. (16 M)

7. a) Derive an expression for the gain of half wave dipole. (8 M)

b) Explain effective aperture area with its types in detail. (8 M)

8. At what distance is the radiation component of magnetic field twice the inductance component? At what distance is it 100 times. (16 M)


UNIT II

WIRE ANTENNAS AND ANTENNA ARRAYS


PART – A (2 MARK)

21. What is meant by cross field?

22. Define axial ratio.

23. What is meant by Beam Area?

24. What is duality of antenna?

25. State Poynting theorem.

26. What is point source?

27. What is meant by array?

28. What is meant by uniform linear array?

29. What are the types of array?

30. What is Broad side array?

31. Define End fire array?

32. What is collinear array?

33. What is parasitic array?

36. Define beam width of major lobe?

37. List out the expression of beam width for broad side array and end fire array.

38. Differentiate broad side and End fire array?

39. What is the need for the Binomial array?

40. Define power pattern?

PART- B (16 MARK)

1. Write short notes on various forms of arrays

i. Broad side array ii. End fire array ii. Collinear array iv. Parasitic array(4 M each)

2. Derive the expression for the far field pattern of an array of 2 – isotropic point sources i) Equal amplitude and phase ii) Equal amplitude and opposite phase(4 M each)

iii) Unequal amplitude and any phase(8 M)

3. Explain the principle of Pattern multiplication. (16 M)

4. Explain the array of N- sources of equal amplitude and spacing- Broad side case i. Direction of pattern maxima ii. Direction of pattern minima (4 M each)

iii. Beam width of major lobe (8 M)

5. Explain the array of N- sources of equal amplitude and spacing- End fire case i) Direction of pattern maxima ii. Direction of pattern minima (4 M each)

iii. Beam width of major lobe (8 M)

6. Write short notes on. i. Binomial arrays ii. Phased arrays (8 M each)


U

NIT III

APERTURE ANTENNAS


PART – A (2 MARK)

41. What is meant by similar Point sources?

42. What is meant by identical Point sources?

43. What is the principle of the pattern multiplication?

44. What is the advantage of pattern multiplication?

45. What is tapering of arrays?

46. What is a binomial array?

47. What are the advantages of binomial array?

48. What is the difference between isotropic and non isotropic source?

49. Define Side Lobe Ratio.

50. List the arrays used for array tapering?

51. What is a Short Dipole?

52. How radiations are created from a short Dipole?

53. Why a short dipole is also called an elemental dipole?

54. What is a Infinitesimal Dipole?

55. Why a short dipole is called a oscillating dipole?

56. What do you understand by retarded current?

57. Define induction field.

58. Define Radiation field.

59. At what distance from the dipole is the induction field equal to the radiation field?

60. Define Radiation Resistance.

PART – B (16 MARK)

1. Explain the different types of lens antenna? (16 M)

2. Explain the radiation from a rectangular aperture? (16 M)

3. Explain the radiation from an elemental area of a plane wave

(or) explain the radiation from a Huygen’s source ? (16 M)

4. Describe the parabolic reflector used at micro frequencies? (16 M)

5. Write short notes on luneberg lens? (16 M)

6. Discuss about spherical waves and biconical antenna? (16 M)

7. Derive the various field components radiated from circular aperture and also find

beamwidth and effective area? (12 M)

8. Derive the field components radiated from a thin slot antenna in an infinite cylinder? (8)


UNIT IV

SPECIAL ANTENNAS AND ANTENNA MEASUREMENTS


PART- A (2 MARK)

61. What is a dipole antenna?

62. What is a half wave dipole?

63. What is the radiation resistance of a half wave dipole?

64. What is a loop antenna?

65. Give an expression of radiation resistance of a small loop

66. How to increase the radiation resistance of a loop antenna?

67. What are Electrically Small loop antennas?

68. What are electrically large loop antennas?

69. List out the uses of loop antenna?

70. What are the parameters to be considered for the design of a helical antenna?

71. What are the types of radiation modes of operation for an helical antenna?

72. Which antenna will produce circularly polarized waves?

75. List the applications of helical antenna?

PART – B (16 MARK)

1. Explain the principle of traveling wave radiator. (16 M)

2. Derive an expression for the radiated field due to a TWA. (16 M)

3. Obtain the expression for the field produced by TWA and compare its radiation with resonant antenna. (16 M)

4. Obtain the expression for the emf due to loop antenna and explain its use as a Direction finder. (16 M)

5. Explain the special features of various types of Horn antennas and frequency independent antennas. (16 M)

6. With a suitable diagram, discuss the construction and operation of a Yagi antenna. (16 )

7. Write detailed notes on (a) Parabolic reflectors (b) Log Periodic antennas (8 M each)

8. (a) Explain the principle of operation and applications of folded dipoles.

(b) With a suitable diagram explain the construction and principle of operation of a log –

periodic antenna. (8 M each)

9. Write short notes on (a) Slot radiators (b) Loop antennas (8 M each)

10. How does a log periodic antenna provide a large bandwidth of operation? (16 M)

11. Explain the principle of operation and applications of loop antenna. (16 M)

12. Write detailed notes on (a) Horn antennas (b) Frequency independent antennas. (8)

13. Explain the principle of operation and applications of loop antenna. (16 M)

14. Explain in detail the working principle of Helical antenna in

(a) Normal mode (b) Axial mode (8 M each)

76. Define Sky wave.


U

NIT V

RADIO WAVE PROPAGATION


PART – A (2 MARK)

77. Define Troposphere wave.

78. Define Ground wave.

79. What are the types of Ground waves?

81. What is meant by Space Wave?

82. What is meant by Surface Wave?

83. What is meant by fading?

84. What are the types of fading?

85. What are inverse and multi path fading?

86. What is meant by diversity reception?

87. Define Space diversity Reception.

88. Define frequency diversity Reception.

89. Define polarization diversity reception.

90. What is meant by Faraday’s rotation?

91. What are the factors that affect the propagation of radio waves?

92. Define gyro frequency.

93. Define critical frequency.

94. Define Magneto-Ions Splitting.

95. Define LUHF.

96. Define Refractive index.

97. Define maximum Usable Frequency.

98. Define skip distance.

99. Define Optimum frequency?

100. Define wave velocity and Group velocity?

PART – B (16 MARK)

1. Explain briefly the various modes of Propagation (16 M)

2. Explain Ground Wave Propagation in detail (16 M)

3. Explain the Structure of Atmosphere (16 M)

4. Explain the various layers of Ionosphere (16 M)

5. Explain the effect of Earth’s Magnetic Field on Radio wave Propagation (16 M)

6. Explain Virtual Height and derive its Expression (16 M)

7. Explain Maximum Usable Frequency and show how to Calculate MUF (16 M)

8. Explain (a) Skip Distance (b) Optimum Working Frequency (8 M each)

9. Explain briefly about Ionospheric abnormalities (16 M)

10. Determine the Effective Earth’s Radius in Space Wave Propagation (16 M)

11. Explain Super Refraction. (16 M)