EC 1352-Antenna and Wave Propagation (Question bank)

UNIT I

RADIATION FIELDS OF WIRE ANTENNAS

PART – A( 2 Marks)

1. Define a Hertzian dipole?
2. Draw the radiation pattern of a horizontal dipole?
3. What do you mean by induction field and radiation field?
4. What is magnetic vector Potential?
5. Define scalar Potential?
6. What is Retarded Current?
7. Write down the expression for magnetic vector Potential using three standard current distributions?
8. Define top loading?
9. What is a capacitance hat?
10. What is quarter wave monopole?
11. Write down the expression for radiated fields of a half wave dipole antenna?
12. What is the effective aperture and directivity of a half wave dipole?
13. What is the effective aperture and directivity of a Hertzian dipole antenna?
14. Write down the expression for radiation resistance of a Hertzian dipole?
15. Define retardation time?
16. What is radiation resistance of a half wave dipole?
17. Compare electric scalar potential and magnetic vector potential?

PART – B

1. Derive the expression for the radiated field from a short dipole? (16)
2. Starting from first principles obtain the expression for the power
radiated by a half wave dipole? (16)
3. Derive the expression for power radiated and find the radiation
resistance of a half wave dipole? (16)
4. Derive the radian resistance, Directivity and effective aperture of a
half wave dipole? (10)
5. Derive the fields radiated from a quarter wave monopole antenna? (8)
6. Find the radiation resistance of elementary dipole with linear
current distribution? (8)
7. Derive the radiation resistance, Directivity and effective
aperture of a hertzian dipole? (10)


UNIT II

ANTENNA FUNDAMENTALS AND ANTENNA ARRAYS

PART – A( 2 Marks)

1. Define array factor?
2. What is the relationship between effective aperture and directivity?
3. Write the principle of pattern multiplication?
4. What is meant by broadside array and end fire array?
5. Define radiation intensity?
6. Define an isotropic antenna?
7. Define a broadside array?
8. Define radiation pattern?
9. What are the two types of radiation pattern?
10. Define Beam solid angle or beam area?
11. Define beam efficiency?
12. Define directivity?
13. Define antenna gain?
14. Define effective aperture?
15. What is collecting aperture?
16. Define HPBW?
17. Define FBR?
18. Define BWFN?
19. Write down the expressions for BWFN for both broadside and end fire array?
20. Differentiate broadside array and end fire array?
21. Write down the expressions for minor lobe maxima and minima for both broadside and end fire array?
22. Define loop antenna?
23. What is axial ratio of a helical antenna?
24. What are advantages of helical antenna?
25. What are the disadvantages of loop antenna?
26. State reciprocity principle?
27. List out the applications helical antenna?
28. Give the expressions for the field components of a helical antenna?
29. Define pitch angle? What happens when =0 and =90?
30. What are applications loop antennas?


PART – B

1. With neat sketch, explain the operation of helical antenna? (16)
2. Obtain the expression for the field and the radiation pattern
produced by a 2 element array of infinitesimal with distance of
separation /2 and currents of unequal magnitude and phase
shift 180 degree? (16)
3. Derive the expression for far field components of a small loop antenna. (16)
4. Derive the expression for electric field of a broadside array of n sources
and also find the maximum direction minimum direction and half power
point direction? (16)
5. Design a 4 element broadside array of /2 spacing between elements
the pattern is to be optimum with a side lobe level 19.1 db.
Find main lobe maximum? (16)
6. Explain pattern multiplication? (8)
7. Derive the expression for electric field of a end fire of n sources
and also find the maximum direction minimum direction and half
power point direction? (16)
8. Write short notes a radiation resistance? (8)
9. Calculate the maximum effective aperture of a /2 antenna? (8)
10. Derive the maxima directions, minima directions, and half
power point direction for an array of two point sources with equal
amplitude and opposite phase? (16)
11. Explain the various types of amplitude distributions in details? (16)


UNIT III

TRAVELING WAVE (WIDE BAND) ANTENNAS

PART – A( 2 Marks)

1. What are traveling wave antenna?
2. What is the type of radiation pattern produced when a wave travels in a wire?
3. Draw the structure of 3-elements yagi-uda antenna and give the dimensions and spacing between the elements in terms of wavelength?
4. What are the applications of log periodic antenna?
5. What are the applications of rhombic antenna?
6. What do you meant by self impedance?
7. What do you meant by mutual impedance?
8. Define traveling wave impedance?
9. What is the main advantage of traveling wave antenna?
10. What are the limitations of rhombic antenna?
11. What are the two types of rhombic antenna design?
12. Define rhombic antenna?
13. Give the expressions for design ratio, spacing factor and frequency ratio, of log periodic antenna?
14. What are the three different regions in log periodic antenna and how they are differentiated?
15. What is frequency independent antenna?
16. What is LPDA?
17. What are the applications of log periodic antenna?

PART – B

1. Explain the radiation from a travelling wave on a wire? (8)
2. What is Yagi-uda Antenna ?Explain the construction and operation of
Yagi-uda Antenna .Also explain its general characteristics? (16)
3. Explain the construction, operation and design for a rhombic antenna? (16)
4. Explain the geometry of a log periodic antenna? Give the design equations and uses of log periodic antenna? (16)
5. Discuss in details about (a) Self impedance (b) Mutual impedance? (8)


UNIT IV

APERTURE AND LENS ANTENNAS

PART – A( 2 Marks)

1. State Huygens Principle?
2. What is Slot Antenna?
3. Which antenna is complementary to the slot dipole?
4. How will you find the directivity of a large rectangular broadside array?
5. What is the relationship between the terminal impedance of slot and dipole antenna?
6. What is the difference between slot antenna and its complementary dipole antenna?
7. Define lens antenna?
8. What are the different types of lens antenna?
9. What is a dielectric lens antenna?
10. What are the drawbacks of lens antenna?
11. What are the field components that are radiated from open end of a coaxial line?
12. What are the advantages of stepped dielectric lens antenna?
13. What is biconical antenna?
14. What is Lunenburg lens?
15. What are the advantages of lens antenna?
16. Mention the uses of lens antenna?
17. How spherical waves are generated?
18. Define the characteristic impedance of biconical antenna?
19. Bring out the expressions for voltage across the feed points of the biconical antenna and current flowing through the surface of the cone?
20. What do you meant by sect oral horn?
21. What do you meant by pyramidal horn?
22. What is back lobe radiation?
23. What are the various feeds used in reflectors?
24. What are the different types of horn antennas?
25. Define refractive index of lens antenna?
26. What are secondary antennas? Give examples?


PART – B

1. Explain the different types of lens antenna? (10)
2. Explain the radiation from a rectangular aperture? (16)
3. Explain the radiation from an elemental area of a plane wave
(or) explain the radiation from a Huygen’s source ? (16)
4. Describe the parabolic reflector used at micro frequencies? (16)
5. Write short notes on luneberg lens? (16)
6. Discuss about spherical waves and biconical antenna? (16)
7. Derive the various field components radiated from circular aperture
and also find beamwidth and effective area ? (12)
8. Derive the field components radiated from a thin slot antenna in
an infinite cyclinder ? (10)
9. Show the relationship between dipole and slot impedances? (8)
10. Explain the radiation from the open end of a coaxial cable? (8)


UNIT V

WAVE PROPAGATION

PART – A ( 2 Marks)

1. Define Gyro frequency?
2. What is multihop Propagation?
3. How spherical waves are generated?
4. What are the effects of earth curvature on tropospheric propagation ?
5. Define critical frequency of an ionized layer of ionosphere?
6. What are the factors that affect the propagation of radio waves?
7. Define ground wave?
8. What are the components present in space wave?
9. Define Fading?
10. Define ionosphere?
11. Define Troposphere?
12. How can minimize Fading?
13. What are the various types diversity reception?
14. Define critical frequency?
15. What is virtual height?
16. Define MUF?
17. State secant law?
18. Define space wave?
19. What are height ranges of different regions in the ionosphere?
20. Write down the expression for the refractive index?
21. What is OWF or OTF?
22. Define duct Propagation?
23. What is skip distance?
24. How will you find the range of space wave propagation or line of sight distances?
25. What is sporadic E layer in ionosphere?


PART – B

1. Explain in details about ionosphere? (8)
2. Explain space wave propagation and sky wave propagation? (16)
3. Explain the ground wave propagation? (8)
4. Discuss the effects of earth’s magnetic field on ionosphere radio wave
propagation? (10)
5. Describe the troposphere and explain how ducts can be used for microwave propagation? (8)
6. Explain in details, the diversity reception methods? (8)
7. Explain the advantages of tropospheric wave propagation and sky wave
propagation? (8)
8. Deduce an expression for the critical frequency of an ionized region in terms of its maximum ionization density? (10)
9. Derive an expression for the refractive index of the ionosphere in terms of
the electron number density and frequency ? (10)