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Radiation and Microwave Techniques (RMT) MCQ with Answer [1-60].


 Radiation and Microwave Techniques (RMT) MCQ with Answer [1-60].

Radiation and Microwave Techniques (RMT) wheebox mcq question with answer for online exam preperation and interview preperation.

Q.no 1. At what position is the input signal inserted into a traveling-wave tube? 

A : At the cathode end of the helix 

B : At the collector 

C : At the collector end of the helix 

D : At the control grid of the electron gun 

Answer :-  A 

Q.no 2. Klystron oscillators are most often used in the frequency range of 

A : 300 to 3000 KHz 

B:  3 to 30 GHz 

C : 30 to 300 MHz 

D : 10 to lO00Hz 

Answer :- B

Q.no 3. Which of the following devices are not being used in microwave power amplifier? 

A : klystron tubes 

B : traveling wave tubes 


D : magnetron 

Answer :- D

Q.no 4. Which of the following is not a microwave tube? 

A : Traveling-wave tube 

B: Cathode-ray tube 

C: Klystron 

D : Magnetron 

Answer :- B

Q.no 5. At microwave frequencies compared to that at short wave band, transmitter and Receiver power requirements are -----

A: very high 

B: very low 

C: medium 

D : extern high 

Answer :- B

Q.no 6. A magnetron is used only as a/an 

A : Amplifier 

B : Oscillator 

C: Mixer 

D : Frequency multiplier 

Answer :- B

Q.no 7. In microwave frequency measurements for microwave power above lOW which of following method used? 

A : Bolometer Technique 

B : Calorimetric Wattmeter 

C : impedance method 

D : Reflectometer 

Answer :- B

Q.no 8. According to Webster's dictionary an antenna is a ____ _ 

A : insulator 

B : amplifier 

C : attenuator 

D : metalic device 

 Answer :- D

Q.no 9. Which among the following is regarded as a condition of an ordinary endfire array? 

A: a< Pd 

B: a> pd 

C: a= ±Pd 

D: a# ±Pd 

Answer :- C

Q.no 10. The Biggest Disadvantage the IMPATT Diode has is its 

A : Low Efficiency 

B : High Noise 

C: LowBW 

D : Inutility to provide Pulse Operation

Answer :- B

Q.no 11. Which of the following is not the passive microwave component? 

A : Circulator 

B: Isolator 

C : Directional coupler 

D : Microwave Transistor 

Answer :- D

Q.no 12. A common application for magnetron is in 

A: Radar 

B : Satellites 

C : Two-way radio 

D: TV sets 

Answer :- A

Q.no 13. The mode of propagation in microstrip line is 

A : Quasi-TEM mode 

B: TEMmode 

C: TM mode 

D: TE mode 

Answer :- A

Q.no 14. Low-power radar transmitters and receivers use which component? 

A : Magnetron 

B :  TWT 

C : Power transistor 

D : Gunn diode 

Answer :- D

Q.no 15. For what are PIN diodes used in microwave? 

A: Mixers 

B : Modulators 

C : Oscillators 

D : Amplifier 

Answer :- B

Q.no 16. Which of the following is used as a high power microwave oscillator? 

A : Thyratron 

B : Magnetron 

C: Klystron 

D : Reflex-klystron 

Answer :- B

Q.no 17. The energy propagation in rectangular waveguide structures is basically a--------- phenomena. 

A : successive reflection 

B : alternate reflection 

C : parallel reflection 

D : alternate and parallel reflection 

Answer :- A

Q.no 18. Which of the following is NOT part of radiation pattern? 

A : Major lobe 

B : Bandwidth 

C : minor lobe 

D : side lobes 

Answer :- B

Q.no 19. The radiation pattern of a half-wave dipole has the shape of a __ _ 

A: Doughnut 

B: Sphere 

C : Hemisphere 

D: Circular 

Answer :- A

Q.no 20. What is the wavelength at frequency of 900 MHz? 

A: 33.3 cm 

B: 33.3 mm 

C: 33.3 nm 

D: 33.3 m 

Answer :- A

Q.no 21. A reflex klystron is used as a(n) 

A : Amplifier 

B : Oscillator 

C: Mixer 

D : Frequency multiplier 

Answer :- B

Q.no 22. In which Microwave device the Microwave source used as local oscillator for frequency measurement? 

A : Magnetron 

B : Traveling wave tube 

C : Double cavity klystron 

D : Reflex Klystron 

Answer :- D

Q.no 23. The most widely used radar transmitter component is a 

A: Klystron 

B : Magnetron 


D : Power transistor 

Answer :- B

Q.no 24. What is the distance between the two shorting plates in cavity resonator to support a signal which bounces back and forth between the two shorting plates 

A: "⋋g/ 2

B: "⋋g/4 

C:   ⋋g

D : 2⋋g

Answer :- C

Q.no 25. Microwave junction is matched at all ports if the S matrix has 

A : all diagonal elements are zero. 

B : all diagonal elements are equal but not zero 

C : all diagonal elements are complex 

D : Hermitian 

Answer :- A

Q.no 26. The main advantage of a TWT over a klystron for microwave amplification is 

A : Lower cost 

B : Smaller size 

C : Higher power 

D : Wider bandwidth 

Answer :- D

Q.no 27. In microwave applications, which of the following is not used cavity resonator 

A : re-entrant cavity resonator 

B : Circular cavity resonator. 

C : Rectangular cavity resonator. 

D : Symmetric Cavity Resonator 

Answer :- D

Q.no 28. Double minimum method is uded for the measuremnt of 

A : Low attenuation Coefficient 

B : High attenuation Coefficient 


D: HighVSWR 

Answer :- C

Q.no 29. To create radiation through wire, there must be _____ _ 

A : Constant current 

B : time varying current 

C : DC current 

D : DC voltage 

Answer :- B

Q.no 30. In order to reduce cross-sectional dimensions, the waveguide to use is 

A: circular 

B: ridged 

C : rectangular 

D: flexible 

Answer :- B

Q.no 31. The standard values of antenna input impedance are __ & __

A: 50 ohm & 75 ohm

B: 50 ohm & lO0 ohm

C: 30 ohm & 75 ohm

D: 25 ohm & 75 ohm 

Answer :- A

Q.no 32. How much current does an antenna draw when radiating 1 kW and is having radiation resistance of 300 n. 


B: 3.5A 


D: 1.8 A 

Answer :- D

Q.no 33. The Correct sequence of frequency bands in order of increasing available peak power is? 

A : C band,X Band,L Band,S band 

B: X band, C band,S Band,L Band 

C: X Band,S Band,C Band,L Band 

D : X band.S Band,L Band,C Band 

Answer :- B

Q.no 34. In TEl0 mode of wave propagation in a rectangular waveguide, if the broader dimension of the waveguide is 40 cm, then the cutoff wavelength for that mode is: 

A: 8cm 

B: 6cm 



Answer :- A

Q.no 35. A vector network analyzer meausres 

A : both magnitude and phase information 

B : only magnitude information 

C : only phase information 

D : neither phase nor magnitude 

Answer :- A

Q.no 36. Isolator works on which of the following phenomanon? 

A : Faraday's rotation 

B : Maxwell's equation 

C : Helmholtz' equation 

D : Boundary conditions 

Answer :- A

Q.no 37. In a satellite communication system, height of satellite is 36,000 km above earth and 

operated at 4 GHz. The gain of transmitting antenna is 20 dB and gain of receiving antenna is 

40 dB. What will be free space transmission loss? 

A: 195.61 dB 

B: 128.61 dB 

C: 178.61 dB 

D: 188.61 dB 

Answer :- A

Q.no 38. One of the commonly used re-entrant cavity is 

A : symmetrical 

B : cicular cavity 

C : rectangular cavity. 

D : co-axial cavity. 

Answer :- D

Q.no 39. Vacuum Tube Eventually Fall at Microwave Frequencies Because of their


A : Inter Electrode Capacitance 

B : Small Series inductance 

C : Large Shunt Capacitance 

D : Short Transit Time 

Answer :- A

Q.no 40. A microwave junction has N no. of ports. The power flows in only one direction in the device. Recognize the device 

A: Isolator 

B : directional coupler 

C : circulator 

D: Gyrator 

Answer :- C

Q.no 41. A wave is said circularly polarized when __ & __

A : El = E2 & c5 = 0 

B : E 1 :;t E2 & 8 = 0 

C : El = E2 & 8 = 90 

D : El :;t E2 & 8 = 90 

Answer :- A

Q.no 42. Varactor and step-recovery diodes are widely used in what type of circuit? 

A : Amplifier 

B : Oscillator 

C : Frequency multiplier 

D: Mixer 

Answer :- C

Q.no 43. Stripline offers a ------ as compare to the microstrip.

A : lower bandwidth 

B : higher bandwidth 

C : medium bandwidth 

D : extrem low 

Answer :- B

Q.no 44. The operating frequency of klystrons and magnetrons is set by the

A : Cavity resonators 

B : DC supply voltage 

C : Input signal frequency 

D : Number of cavities 

Answer :- A

Q.no 45. For most of the micro strip substrates: 

A : Conductor loss is more significant than di electric loss 

B : Di electric loss is more significant than conductor loss 

C : Conductor loss is not significant 

D : Di-electric loss is less significant 

Answer :- A

Q.no 46. What will be the radiation efficiency of antenna if the values of radiation resistance and loss resistance is 72 !l & 8 !l respectively. 

A: 0.45 

B: 0.85 

C: 0.9 

D: 0.98 

Answer :- C

Q.no 47. An antenna is having field pattern given by E(O) = cos O, for 00 < 0 < 900. Find the HPBW in degree. 

A: 180 

B: 90 

C: 45 

D: 270 

Answer :- B

Q.no 48. Which of the following is considered as the major advantage of using a helix traveling wave tube? 

A :  Cheaper 

B : Less noise 

C : High power 

D : Wide bandwidth 

Answer :- D

Q.no 49. In television systems the characteristic impedance of the cables used is: 

A: 50 Ohm

B: 75 Ohm

C: 100 Ohm

D: 150 Ohm

Answer :- B

Q.no 50. High-power TWTs are replacing what in microwave amplifiers? 


B : Magnetrons 

C:  Klystrons 

D : IMPATT diodes 

Answer :- C

Q.no 51. Wave impedance does not depend on which of the following parameters? 

A : Type of line or guide 

B: The material 

C : Operating frequency 

D : Phase of the signal 

Answer :- D

Q.no 52. For the dominant mode, in a rectangular waveguide with bredth 10cm guide wavelengthof a signal 2.5GHz 

A: 12 cm 

B: 15 cm 

C: 20 cm 

D: 18 cm 

Answer :- B

Q.no 53. As the electron beam moves through a klystron's intercavity drift space 

A : Frequency modulation at the input cavity creates velocity modulation at the output cavity 

B : Velocity modulation at the input cavity creates density modulation at the output cavity 

C : Density modulation at the input cavity creates velocity modulation at the output cavity 

D : Phase modulation at the input cavity creates velocity modulation at the output cavity.

 Answer :- B

Q.no 54. Calculate Reflected Power if Two identical 30dB directional couplers are used to sample incident & reflected power in waveguide having VSWR=2 & output of the coupler sampling incident power=4.5m W 

A: 0.82 W 

B: 0.45W 


D: 0.35 W 

Answer :- C

Q.no 55. The higher order wave guide modes of propagation can be avoided in a strip line by: 

A : Restricting both the ground plate spacing and the sidewall width to less than ld/2 

B : Restricting both the ground facing plate spacing and the sidewall width to less than Ad 

C : Filling the region between 2 plates with di electric 

D : Restricting both the ground plate spacing and the sidewall width between lg and lg/2 

Answer :- A

Q.no 56. A magnetron is operated at a duty cycle of 0.001. It has a peak power output of 100 kilowatts. Its average power is 

A : 10,000 watts 

B: 100 watts 

C : 1,000 watts 

D: 1,000,000 watts 

Answer :- B

Q.no 57. A reflex klystron is oscillating at the frequency of its resonant cavity. If the reflector voltage is made slightly less negative, the 

A : Oscillation will cease 

B : Output power would increase 

C : The frequency will decrease 

D : Bunching would occur earlier in time 

Answer :- C

Q.no 58. Two identical directional coupler (20 dB) in waveguide are used to sample a incident and reflected powers. Output of two couplers is 3 mw and 0.1 mw respectively 

Find: 1) Value ofVSWR in main waveguide. 

A: 1.1 

B: 1.44 

C: 1.21 

D: 1.3 

Answer :- B

Q.no 59. For an air-filled rectangular waveguide of 2 cm ' 1 cm, calculate the cut-off wavelength le for TElO and TMll modes. Also calculate guide wavelength at 10 GHz. 

A: 5.5cm 

B: 4.5cm 


D: 4.75cm 

Answer :- B

Q.no 60. Indicate the false statement. Transit time in microwave tubes will be reduced if 

A : the electrodes are brought closer together 

B : a higher node current is used 

C : multiple or coaxial loads are used 

D : the anode voltage is made larger

Answer :-  C

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