# 300+ TOP ANTENNA and WAVE PROPAGATION Objective Questions

## ANTENNA and WAVE PROPAGATION Objective Questions and Answers :-

1. What is the wavelength of Super high frequency (SHF) especially used in Radar & satellite communication?

A. 1 m – 10 m
B. 1 cm – 10 cm
C. 10 cm – 1 m
D. 0.1 cm – 1 cm

Ans: 1 cm – 10 cm

2. Which among the following is an application of high frequency?

A. SONAR
B. Subsurface communication
D. Facsimile

Ans: Facsimile

3. Wavefront is basically a locus of points acquiring similar _______

A. Phase
B. Frequency
C. Amplitude
D. Wave equation

Ans: Phase

4. In which kind of waveform is the phase velocity defined?

A. Sinusoidal
B. Rectangular
C. Square
D. Triangular

Ans: Sinusoidal

5. Which among the following is/are not present in free space?

A. Solid bodies
B. Ionized particles
C. Interference of normal radiation & radio wave propagation
D. All of the above

Ans: All of the above

6. Power density is basically termed as ________ power per unit area

A. Reflected
B. Refracted
D. Diffracted

7. If the path difference of two waves with single source traveling by different paths to arrive at the same point, is λ/2, what would be the phase difference between them?

A. β x (λ/2)
B. β / (λ/2)
C. β + (λ/2)
D. β – (λ/2)

Ans: β x (λ/2)

8. Which ionization layer exists during day time & usually vanishes at night due to highest recombination rate?

A. D-region
B. Normal E-region
D. Appleton region

Ans: D-region

9. What is the possible range of height for the occurrence of sporadic E-region with respect to normal E-region?

A. 20 km – 50 km
B. 45 km – 85 km
C. 90 km – 130 km
D. 140 km – 200 km

Ans: 90 km – 130 km

10. F2 layer of appleton region acts as a significant reflecting medium for _____ frequency radio waves

A. Low
B. Moderate
C. High
D. All of the above

Ans: High

11. The knowledge of which parameter is sufficient for deriving the time varying electromagnetic field?

A. Electric field intensity
B. Magnetic field intensity
C. Current density
D. Power density

Ans: Current density

12. According to Webster’s dictionary, what is an antenna?

A. Impedance matching device
B. Sensor of electromagnetic waves
C. Transducer between guided wave & free space wave
D. Metallic device for radiating or receiving radio waves

Ans: Metallic device for radiating or receiving radio waves

13. Under which conditions of charge does the radiation occur through wire antenna?

A. For a charge with no motion
B. For a charge moving with uniform velocity with straight & infinite wire
C. For a charge oscillating in time motion
D. All of the above

Ans: For a charge oscillating in time motion

14. In a non-isotropic directional antenna, which radiating lobe axis makes an angle of 180° w.r.t. major beam of an antenna?

A. Minor lobe
B. Side lobe
C. Back lobe
D. None of the above

Ans: Back lobe

15. At which angles does the front to back ratio specify an antenna gain?

A. 0° & 180°
B. 90° & 180°
C. 180° & 270°
D. 180° & 360°

Ans: 0° & 180°

16. Which among the following defines the angular distance between two points on each side of major lobe especially when the radiation drops to zero?

A. Half power beam width (HPBW)
B. First null beam width (FNBW)
C. Side lobe level (SLL)
D. Front to back ratio (FBR)

Ans: First null beam width (FNBW)

17. If an observation point is closely located to the source, then the field is termed as ________

A. Induced
C. Reflected
D. Far-field

Ans: Induced

18. Which waveform plays a crucial role in determining the radiation pattern of the dipole/wire antennas?

A. Current
B. Voltage
C. Frequency
D. Phase

Ans: Current

19. How are the infinitesimal dipoles represented in terms of antenna length and signal wavelength?

A. l ≤ (λ /50)
B. (λ/50 ) < l ≤ (λ /10)
C. l = λ/2
D. None of the above

Ans: l ≤ (λ /50)

20. In flared transmission line, the radiation phenomenon increases due to ________ in flaring

A. Increase
B. Decrease
C. Stability
D. None of the above

Ans: Increase

21. Which pattern is generated due to plotting of square of amplitude of an electric field?

A. Field Pattern
B. Voltage Pattern
C. Power Pattern
D. All of the above

Ans: Power Pattern

22. In an electrically small loops, the overall length of the loop is ______ one-tenth of a wavelength.

A. Less than
B. Equal to
C. Greater than
D. None of the above

Ans: Less than

23. On which factor/s do/does the radiation field of a small loop depend?

A. Shape
B. Area
C. Both a and b
D. None of the above

Ans: Area

24. From the radiation point of view, small loops are _________radiators

A. Poor
B. Good
C. Better
D. Excellent

Ans: Poor

25. According to the directivity of a small loop, which value of ‘θ’ contributes to achieve the maximum value of radiation intensity (Umax)?

A. 0°
B. 90°
C. 180°
D. 270°

Ans: 90°

26. In which kind of array configuration, the element locations must deviate or adjust to some nonplaner surface like an aircraft or missile?

A. Linear
B. Planer
C. Conformal
D. All of the above

Ans: Conformal

27. What is the nature of radiation pattern of an isotropic antenna?

A. Spherical
B. Dough-nut
C. Elliptical
D. Hyperbolic

Ans: Spherical

28. In broadside array, all the elements in the array should have similar _______excitation along with similar amplitude excitation for maximum radiation.

A. Phase
B. Frequency
C. Current
D. Voltage

Ans: Phase

29. Which among the following is regarded as a condition of an ordinary endfire array?

A. α < βd B. α > βd
C. α = ±βd
D. α ≠ ±βd

Ans: α = ±βd

30. Which mode of propagation is adopted in HF antennas?

A. Ionospheric
B. Ground wave
C. Tropospheric
D. All of the above

Ans: Ionospheric

31. For which band/s is the space wave propagation suitable over 30 MHz?

A. VHF
B. SHF
C. UHF
D. All of the above

Ans: All of the above

32. If the tower antenna is not grounded, which method of excitation is/are applicable for it?

A. Series
B. Shunt
C. Both a and b
D. None of the above

Ans: Series

33. In ungrounded antennas, if an excitation is applied directly across the base insulator, then on which factor/s would the voltage across the insulator depend?

A. Power delivered to antenna
B. Power factor of impedance
C. Both a and b
D. None of the above

Ans: Both a and b

34. Which among the following exhibits perpendicular nature in TEM wave?

A. Electric field
B. Magnetic field
C. Direction of propagation
D. All of the above
Ans: All of the above

35. Which equations are regarded as wave equations in frequency domain for lossless media?

A. Maxwell’s
B. Lorentz
C. Helmholtz
D. Poisson’s

Ans: Helmholtz

36. If the magnetic field component of a plane wave in a lossless dielectric is H = 50 sin (2π x 106 t – 6x) azmA/m , what will be the wave velocity?

A. 1.047 x 106 m/s
B. 1.257 x 106 m/s
C. 2.50 x 106 m/s
D. 3 x 106 m/s

Ans: 1.047 x 106 m/s

37. In an electrical circuit,which nature of impedance causes the current & voltages in phase?

A. Reactive
B. Resistive
C. Capacitive
D. Inductive

Ans: Resistive

38. Which type of ground wave travels over the earth surface by acquiring direct path through air from transmitting to receiving antennas?

A. Surface wave
B. Space wave
C. Both a & b
D. None of the above

Ans: Space wave

39. After which phenomenon/phenomena do the waves arrive at the receiving antenna in ionospheric propagation?

A. Reflection or Scattering
B. Refraction
C. Defraction
D. All of the above

Ans: Reflection or Scattering

40. By which name/s is an ionospheric propagation, also known as?

A. Sea wave propagation
B. Ground wave propagation
C. Sky wave propagation
D. All of the above

Ans: Sky wave propagation

41. According to Snell’s law in optics, if a ray travels from dense media to rarer media, what would be its direction w.r.t the normal?

A. Towards
B. Away
C. Across
D. Beside

Ans: Away

42. Which mechanism/s is/are likely to occur in mid-frequency operation corresponding to ionospheric region?

A. Only Reflection
B. Only Refraction
C. Partial reflection & refraction
D. None of the above

Ans: Partial reflection & refraction

43. Which among the following plays a primary role in generation of conduction current in an ionosphere due to presence of electric field?

A. Ions
B. Motion of electrons
C. Neutral molecules
D. None of the above

Ans: Motion of electrons

44. Which type of wire antennas are also known as dipoles?

A. Linear
B. Loop
C. Helical
D. All of the above

Ans: Linear

45. Which antennas are renowned as patch antennas especially adopted for space craft applications?

A. Aperture
B. Microstrip
C. Array
D. Lens

Ans: Microstrip

46. Which conversion mechanism is performed by parabolic reflector antenna?

A. Plane to spherical wave
B. Spherical to plane wave
C. Both a and b
D. None of the above

Ans: Spherical to plane wave

47. Which antenna radiating region/s has/have independent nature of angular field distribution over the distance from the antenna?

A. Reactive near-field region
B. Fresnel region
C. Fraunhofer region
D. All of the above

Ans: Fraunhofer region

48. Sterdian is a measurement unit of __________

A. Point angle
B. Linear angle
C. Plane angle
D. Solid angle

Ans: Solid angle

49. According to the geometry, how many sterdians are present in a full sphere?

A. π/2
B. π
C. 2π
D. 4π

Ans: 4π

50. The vector magnetic potential shows the inverse relationship with its ____

A. Source
B. Distance of point from the source (R)
C. Both a and b
D. None of the above

Ans: Distance of point from the source (R)

### ANTENNA and WAVE PROPAGATION Multiple Choice Questions ::

51. In retarded potentials, what factor of time delay is generally introduced in A & V equations?

A. R + c
B. R – c
C. R/c
D. R x c

Ans: R/c

52. In the solutions of inhomogeneous vector potential wave equation, which component exists if the source is at origin and the points are removed from the source (Jz = 0)?

A. Inward
B. Outward
C. Both a and b
D. None of the above

Ans: Outward

53. If a half-wave dipole operates at 300 MHz with λ = 0.5m & D0 = 1.643, what will be its effective area?

A. 0.032 m2
B. 0.047 m2
C. 0.65 m2
D. 0.99 m2

Ans: 0.032 m2

54. Dipole antenna is symmetrical in nature where the two ends are at equal potentials with respect to _____point

A. Initial
B. Eventual
C. Mid
D. None of the above

Ans: Mid

55. Which term is regarded as an inductive field as it is predictable from Biot Savart law & considered to be of prime importance at near field or the distance close to current element?

A. 1/ r
B. 1/ r2
C. 1/ r3
D. 1/ r4

Ans: 1/ r2

56. What is the nature of current distribution over the small dipoles?

A. Spherical
B. Rectangular
C. Triangular
D. Square

Ans: Triangular

57. For receiving a particular frequency signal, which tuning component must be used by the loop to form a resonant circuit for tuning to that frequency?

A. Capacitor
B. Inductor
C. Resistor
D. Gyrator

Ans: Capacitor

58. If the radius of loop is λ/ 20 in a free space medium,what will be the radiation resistance of 8-turn small circular loop?

A. 0.7883 Ω
B. 50.45 Ω
C. 123.17 Ω
D. 190.01 Ω

Ans: 123.17 Ω

59. What is the far-field position of an electric short dipole?

A. Along x-axis
B. Along y-axis
C. Along z-axis
D. Along xy plane

Ans: Along z-axis

60. What would happen if the rms value of induced emf in loop acquires an angle θ = 90°?

A. Wave is incident in direction of plane of the loop with induced maximum voltage
B. Wave is incident normal to plane of the loop with no induced voltage
C. Wave is incident in opposite direction of plane of the loop with minimum voltage
D. None of the above

Ans: Wave is incident normal to plane of the loop with no induced voltage

61. If a linear uniform array consists of 9 isotropic elements separated by λ/4, what would be the directivity of a broadside array in dB?

A. 6.53 dB
B. 7.99 dB
C. 8.55 dB
D. 9.02 dB

Ans: 6.53 dB

62. If the elements of a binomial array are separated by λ/4, how many shape patterns are generated with no minor lobes?

A. 2
B. 4
C. 8
D. 16

Ans: 8

63. What kind of beamwidth is/are produced by Chebyshev arrays for given side lobe level (SLL)?

A. Widest
B. Narrowest
C. Both a and b
D. None of the above

Ans: Narrowest

64. If the length of elements of an array is greater than λ/2, which will be the operating region of an array?

A. Transmission line region
B. Active region
C. Reflective region
D. All of the above

Ans: Reflective region

65. Which angle of rhombic antenna represents one half of included angle of two legs of one wire?

A. Apex angle
B. Tilt angle
C. Both a and b
D. None of the above

Ans: Tilt angle

66. Which among the following is not a disadvantage of rhombic antenna?

A. Requirement of large space
B. Reduced transmission efficiency
C. Maximum radiated power along main axis
D. Wastage of power in terminating resistor

Ans: Maximum radiated power along main axis

67. Why are beverage antennas not used as transmitting antenna?

A. Low radiation resistance
B. Low radiation efficiency
C. Both a and b
D. None of the above

Ans: Both a and b

68. Which kind of polarization is provided by helical antennas?

A. Plane
B. Elliptical
C. Circular
D. All of the above

Ans: Circular

69. According to depth of penetration, what is the percentage proportion of attenuated wave w.r.t its original value?

A. 17%
B. 27%
C. 37%
D. 57%

Ans: 37%

70. Linear polarization can be obtained only if the wave consists of ________

A. Ex
B. Ey
C. Both Ex & Ey & in phase
D. Both Ex & Ey & out of phase

Ans: Both Ex & Ey & in phase

71. When an electromagnetic wave travels from transmitter to receiver, which factor/s affect/s the propagation level?

A. Curvature of earth
B. Roughness of earth
C. Magnetic field of earth
D. All of the above

Ans: All of the above

72. For avoiding ground losses, better is the surface conductivity, less is the __________

A. Attenuation
B. Phase velocity
C. Propagation constant
D. Tilt angle

Ans: Attenuation

73. On which factors of earth does the magnitude of tilt angle depend in surface wave?

A. Permittivity
B. Conductivity
C. Resistivity
D. Reflectivity

A. A & B
B. C & D
C. A & C
D. B & D

Ans: A & B

74. What is the direction of varying orientation of polarized surface wave at the earth surface in a wave tilt mechanism?

A. Horizontal
B. Vertical
C. Diagonal
D. Opposite

Ans: Vertical

75. Which layer has the atmospheric conditions exactly opposite to that of standard atmosphere?

A. Depression layer
B. Regression layer
C. Inversion layer
D. Invasion layer

Ans: Inversion layer

76. If the maximum electron density for F-layer in ionosphere is 4 x 106 electrons/cm3, then what will be the critical frequency of EM wave for F-layer?

A. 4 MHz
B. 9 MHz
C. 18 MHz
D. 25 MHz

Ans: 18 MHz

77. According to Secant law, which frequency is greater than critical frequency by a factor of secθi?

A. MUF
B. LUF
C. OWF
D. UHF

Ans: MUF

78. How is the effect of selective fading reduced?

A. By high carrier reception
B. By low carrier reception
C. By single side band system
D. By double side band system

A. A & C
B. B & D
C. A & D
D. B & C

Ans: A & C

79. In lens antenna, what kind of wave energy is transformed into plane waves?

A. Convergent
B. Divergent
C. Contingent
D. Congruent

Ans: Divergent

80. What is the functioning role of an antenna in receiving mode?

B. Converter
C. Sensor
D. Inverter

Ans: Sensor

81. In radio communication link, what is the shape/nature of waves generated by transmitting antenna?

A. Spherical
B. Plane
C. Triangular
D. Square

Ans: Spherical

82. Which among the following elucidate the generation of electromagnetic waves?

A. Ampere’s law
C. Gauss’s law
D. Kirchoff’s law

A. A & B
B. B & C
C. A & C
D. B & D

Ans: A & B

83. If an antenna draws 12 A current and radiates 4 kW, then what will be its radiation resistance?

A. 22.22 ohm
B. 27.77 ohm
C. 33.33 ohm
D. 39.77 ohm

Ans: 27.77 ohm

84. Under which conditions of two unit vectors, the polarization loss factor (PLF) is equal to unity?

A. Perpendicular
B. Perfectly aligned
C. Angle inclination (Ψp)
D. All of the above

Ans: Perfectly aligned

85. Which property/ies of antenna is/are likely to be evidenced in accordance to Reciprocity theorem?

A. Equality of impedances
B. Equality of directional patterns
C. Equality of effective lengths
D. All of the above

Ans: All of the above

86. Self impedance of an antenna is basically __________

A. Its input impedance during the removal of all other antennas
B. Its impedance by taking into consideration the consequences of other antennas
C. Both a and b
D. None of the above

Ans: Its input impedance during the removal of all other antennas

87. In solution evaluation process of inhomogeneous vector potential wave equation, if points are completely removed from the source, then by which factor does the time varying field & static solution differ?

A. e-jkr
B. ejkr
C. e-jk/r
D. e(jk + r)

Ans: e-jkr

88. The concept of magnetic vector potential finds its major application in deriving expression of magnetic field intensity especially for ______

A. Real fields
B. Imaginary fields
C. Complex fields
D. None of the above

Ans: Complex fields

89. A dipole carries r.m.s. current of about 300A across the radiation resistance 2 Ω. What would be the power radiated by an antenna?

A. 90 kW
B. 135 kW
C. 180 kW
D. 200 kW

Ans: 180 kW

90. What is/are the major applications of an infinitesimal dipole that contribute/s to its analysis?

A. Field pattern estimation due to any length of antenna
B. Improvement in radiation resistance by increasing dipole length
C. Both a and b
D. None of the above

Ans: Both a and b

91. What is /are the advantages of using ferrite loops?

A. Increase in Magnetic field intensity
B. Increase in radiation resistance
C. Decrease in Magnetic field intensity
D. Decrease in radiation resistance

A. A & B
B. C & D
C. A & D
D. B & C

Ans: A & B

92. In an electrically large loop, an overall length of the loop is equal to ______

A. λ/2
B. λ
C. λ/10
D. λ/50

Ans: λ

93. How do the elements of an active region behave?

A. Inductive
B. Capacitive
C. Resistive
D. None of the above

Ans: Resistive

94. By how many times is an input impedance of a folded dipole at resonance greater than that of an isolated dipole with same length as one of its sides?

A. 2
B. 3
C. 4
D. 6

Ans: 4

95. Which mode of radiation occurs in an helical antenna due to smaller dimensions of helix as compared to a wavelength?

A. Normal
B. Axial
C. Both a and b
D. None of the above

Ans: Normal

96. A rectangular horn antenna operating at 4GHz has the wavelength of 0.075m and gain of about 13dBi. What will be its required capture area?

A. 0.0149 m2
B. 0.0475 m2
C. 0.5521 m2
D. 0.9732 m2

Ans: 0.0149 m2

97. What is/are the major applications of an infinitesimal dipole that contribute/s to its analysis?

A. Field pattern estimation due to any length of antenna
B. Improvement in radiation resistance by increasing dipole length
C. Both A and B
D. None of the above

Ans: Both A and B

98. What is /are the advantages of using ferrite loops?

A. Increase in Magnetic field intensity
B. Increase in radiation resistance
C. Decrease in Magnetic field intensity
D. Decrease in radiation resistance

A. A & B
B. C & D
C. A & D
D. B & C

Ans: A & B

99. The concept of magnetic vector potential finds its major application in deriving expression of magnetic field intensity especially for ______

A. Real fields
B. Imaginary fields
C. Complex fields
D. None of the above

Ans: Complex fields

100. A dipole carries r.m.s. current of about 300A across the radiation resistance 2 Ω. What would be the power radiated by an antenna?

A. 90 kW
B. 135 kW
C. 180 kW
D. 200 kW

Ans: 180 kW