# Micro Wave Engineering 5

Electronic Engineering MCQ Question Papers: ENTC, IT Interview Placement

Subject: Micro Wave Engineering 5

Part 5: List for questions and answers of Micro Wave Engineering

Q1. Microwave links are typically 50 km apart

a) Because of atmospheric attenuation

b) Because of output tube power limitation

c) Because of earth’s curvature

d) To ensure that applied dc voltage is not excessive

Q2. For matching over a range of frequencies in a transmission line it is best to use

a) A balun

b) A broad band directional coupler

c) Double stub

d) A single stub of adjustable position

Q3. Which of the following is wrong for a magic used to tee?

a) E and h arms are decoupled

b) Coplanar arms are coupled

c) All ports are perfectly matched

d) A signal into coplanar arm splits equally between e and h arms

Q4. Assertion (a): impedance matching can be done by using stubs Reason (r): a double stub is used for impedance matching when frequency of signal varies

a) Both a and r are correct and r is correct explanation of a

b) Both a and r are correct but r is not correct explanation of a

c) A is correct but r is wrong

d) A is wrong but r is correct

Q5. Assertion (a): pin diode is used as a fast switch Reason (r): pin diode has very high resistance when reverse biased and very low resistance when forward biased

a) Both a and r are correct and r is correct explanation of a

b) Both a and r are correct but r is not correct explanation of a

c) A is correct but r is wrong

d) A is wrong but r is correct

Q6. Assertion (a): impedance measurement at microwave frequencies is done by finding swr Reason (r): swr and reflection coefficient depend on the characteristic impedance and load impedance

a) Both a and r are correct and r is correct explanation of a

b) Both a and r are correct but r is not correct explanation of a

c) A is correct but r is wrong

d) A is wrong but r is correct

Q7. Which device has internal positive feedback?

a) Two cavity klystron amplifier

b) Multi-cavity klystron amplifier

c) Reflex klystron amplifier

d) All of the above

Q8. The domain mode in rectangular waveguide is

a) Te01

b) Te02

c) Te10

d) Tm11

Q9. The reverse voltage applied to a varactor diode

a) Is less than avalanche breakdown voltage

b) Is more than avalanche breakdown voltage

c) May be more or less than a avalanche breakdown voltage

d) Is very high as compared to avalanche breakdown voltage

Q10. To ensure that only dominant mode te10 is allowed to propagate in an air filled rectangular waveguide, the lower frequency limit and upper frequency limit are

a) About 25% above fc for te10 and 5% below fc for te20 mode respectively

b) About 50% above fc for te10 and 25% below fc for te20 mode respectively

c) About 25% above fc for te10 and 25% below fc for te20 mode respectively

d) None of the above

Q11. The skin depth at 1000 mhz as compared to that at 500 mhz is

a) 2

b) 12

c) 0.707

d) 0.5

Q12. Pin diode has

a) P+ and n layers separated by i layer

b) P+ and n+ layers separated by i layer

c) P- and n- layers separated by i layer

d) None of the above

Q13. The two terms used to describe performance of a directional coupler are

a) Coupling and directivity

b) Gain and coupling

c) Gain and directivity

d) Gain and isolation

Q14. The number of pm radio channels which can be accommodated in a spectrum of 300 mhz is about

a) 10

b) 100

c) 500

d) 1500

Q15. Assertion (a): microstrip is very commonly used in microwave integrated circuits Reason (r): microstrip has an easy access to the top-surface so that active and passive discrete components can be easily mounted

a) Both a and r are correct and r is correct explanation of a

b) Both a and r are correct but r is not correct explanation of a

c) A is correct but r is wrong

d) A is wrong but r is correct

Q16. A 75 ohm line is first short terminated and minima locations are noted. Then the short is replaced by resistive load and minima location are again noted. If minima location are not altered and vswr is 3, the value of resistive load is

a) 25 ohm

b) 50 ohm

c) 225 ohm

d) 250 ohm

Q17. The word ‘loran’ means

b) Long range tv transmission

c) Long range cable transmission

d) Either (b) or (c)

Q18. In a klystron amplifier the bunching effect

a) Converts velocity modulation into current modulation of beam

b) Converts current modulation into velocity modulation of beam

c) Both (c) and (b)

d) Neither (a) nor (b)

Q19. A te10 rectangular waveguide is to be designed for operation over 25-35 ghz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is

a) 15 mm

b) 10 mm

c) 9 mm

d) 7.5 mm

Q20. In a klystron amplifier the force on all electrons

a) Causes acceleration of all electrons

b) Causes retardation of all electrons

c) Causes acceleration of some electrons and retardation of others

d) None of the above

Part 5: List for questions and answers of Micro Wave Engineering