Microwave Introduction Objective Questions

8/11/2019 Microwave Introduction Objective Questions

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Objective Question Bank Unit 1

ECE Dept, Sreyas Institute of Engineering & Technology Microwave Engineering

UNIT -1

OBJECTIVE QUESTIONS

Choose the corr ect alternative.

1. The range of microwave frequencies is given by [ ]

a) 1 GHz to 300 GHz b) 1 MHz to 300 MHz

c) 1 KHz to 300 kHz d) None

2. In which of the following application does microwaves [ ]

a) Tele communications b) RADARs

c) Radio Astronomy d) All the above

3. Which of the following are advantages of microwaves [ ]

a) High directivity b) High bandwidth

c) Reliabilty d) All the above

4. As the frequency increases the beam width and directivity [ ]

a) Decreases, decreases b) Decreases , increases

c) Increases, decreases d) Increases, increases

5. The velocity of light C interms of permiablity 0,0in space is given by [ ]a) c = (0/ 0) b) c = (0/ 0)c) c = (0*0) d) None

6. Which of the following gives the cutoff frequency fc, where c= velocity of light,

m,n = mode numbers, a,b= dimensions of waveguide [ ]

a)fc=c/2 * (m/a)2 + (n/b)2 b) fc=c/2 * (m/a)

2 - (n/b)2

c) fc=c/2 * (m/a)2* (n/b)2 d) None

7. For a dominent mode the value of cutoff wave length is [ ]a) Zero b) Minimum

c) Maximum d) None

8. which of the following is the dominent mode in TMmn wave guide [ ]

a) TM12 b) TM21 c) TM11 d) TM22

9. The rate at which the wave changes its phase is called [ ]

a) Phase velocity b) Group velocity

c) Particle velaocity d) None

10. The constant interms of guide wave length gis [ ]a) = 2/ g b) = g/2 c) = 2/ g

2 d) = g2/2

11. The phase velocity Vp is given by which of the following [ ]

a) Vp= / b) Vp= / c) Vp= /2 d) None


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12. What is the value of cutoff wave length for the dominent waves [ ]a) c11 = 2ab/(a

2-b2) b) c11 = 2ab/(a2+b2)

c) c11 = (a2-b2)/ 2ab d) none

13. The Wavelength correspond to Microwave frequency range is 3-30 GHz is [ ]

a) 100-10 cm b) 10-1cm c) 1-0.1 cm d) 0.1-0.001cm

14.The main advantage of microwave is that- [ ]

a) Highly Directive. b) Moves at the speed of light.

c) S/N ratio grater. d) High penetration power.

15. In a rectangular waveguide, which of the following modes are known as the degenerate modes [ ]

a) TE01

and TE10

b) TE11

and TM11

c) TM01

and TM10

d) TE01

and TM01

16. The electric and magnetic fields inside the waveguide can be determined by solving from

______________ equations subject to the appropriate boundary conditions [ ]

a)Thevenins b) Nortons c) Faradays d) Maxwells

17. Generally Waveguides are not preferred below the frequencies of [ ]

a) 1 GHz b) 25GHz c) 50 GHz d) 100 GHz

18. ________ is defined as the rate at which the wave propagates through the waveguide [ ]

a) Phase Velocity b) Group Velocity c) Guide Velocity d) Wave Velocity

19. The frequency bands above 1 GHz are referred to as __________frequency bands [ ]

a) Milliwave b) Low c) Microwave d) Very low

20. A joint discontinuity in a wave guide [ ]

a) Independent of frequency b) increases at low frequency

c) increases at higher frequency d) decreases at higher frequency

21. A Piston attenuation is [ ]

a)Flap attenuator b)Waveguide below cutoffc)Vane attenuator d)Mode filter

22. Which one of the following modes does not exist in waveguides [ ]

a)TE b)TM c)TEM d)None

23. For handling large microwave power, the best medium is [ ]

a) Coaxial line b) Rectangular waveguide

c) Stripline d) Circular waveguide

24. A waveguide section in a microwave circuit will act as a [ ]

a) Low-pass filter b) Band-pass filter c) High-pass filter d) Band-reject filter


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25. Microwave antenna aperture efficiency depends on [ ]

a) Feed Pattern b) Antenna Aperture c) Surface losses d) Low side lobe level

26. Microwave frequency range extends from [ ]

a) 3 MHz to 30 MHz b) 30 MHz to 300 MHz

c) 300 MHz to 3000 MHz d) 500 MHz to 30000 MHz

27. At microwave frequencies the size of the antenna becomes [ ]

a) Very large b) Large c) Small d) Very Small

28. The phenomenon of microwave signals following the curvature of earth is known as [ ]

a) Faraday effect b) Ducting c) Wave tilt d) Troposcatter

29. In microwave communication links, the rain drop attenuation experienced is mainly due to [ ]

a) Absorption of microwave energy by water vapour

b) resonance absorption of atomic vibration in water molecules

c) scattering of microwaves by collection of water drops

d) refraction of microwaves through liquid-drop lenses formed by rain

30) Which of the following is the dominant mode in TE wave? [ ]

a) TE00 b) TE01 c) TE11 d) TE10

Note: F il l the foll owing blanks with suitable answer

31. The dominant mode attenuation factor due to finite conductivity () of the waveguide walls isproportional to________.

32. At the cut-off frequency, the dominant mode characteristic impedance of a rectangular waveguide is

_______________.

33. Typical frequency range of X-band is ____________G Hz .

34. At the cut-off frequency, the TM11

mode characteristic impedance of a rectangular waveguide is _

_______ ohms.

35. The mode with the lowest cutoff frequency in a particular guide is called the __________mode .

36. When microwave signals follow the curvature of the earth this is known as ___________ .

37. When electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is

_________________ in the actual direction of propagation.

38. To reduce loses at high frequencies, wave guides are plated with _____________.

39. A waveguide below cut-off is also called ______________ .


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40. _____________Mode exists in TM wave of rectangular waveguide as dominant mode.

41. Wave impedance for TM wave in rectangular guide in ZTM= _________________.

42. The Helmholtzs wave equation for TE & TM wave travelling in Z direction of a wave guides are ___________________.

43. Hollow _______________are commonly used as transmission lines at frequencies above

5 GHz.

44. All the TM0m

and TM1m

modes are degenerate in a uniform __________________waveguide.

45. All intersection between electric and magnetic field lines in a waveguide is _____________.

Key:

1. a 2. d 3. d 4. b 5. c 6. a 7. c 8. c 9. a 10. a

11. b 12. b 13. b 14. a 15. b 16.d 17.a 18.c 19.c 20. c

21. b 22.c 23.b 24.c 25.b 26.d 27.d 28. b 29. a 30. d

31. (1/ ) 32. Infinity

33. 8 to 12 34. Zero

35. Dominant 36. Ducting

37. Greater than 38. Gold

39. Piston attenuator 40. TM11

41. / 1-(0/ c)2 42. 2Hz=0 &

2Ez=0

43. waveguides_or tubes 44. Rectangular

45. Perpendicular

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Microwave Introduction Objective Questions