1. A reflex Klystron fuctions asa) Microwave oscillatorb) Microwave amplifierc) Both as Microwave amplifier and oscillatord) A high gain cavity

Ans: Option a)

2. The modes in a reflex Klystrona) give the same frequency but different transit timesb) result from excessive transit time across the resonator gapc) are caused by spurious frequency modulationd) are just for theoretical considerations

Ans: Option a)

3. Klystron operates on the principle ofa) Amplitude Modulationb) Frequency Modulationc) Pulse Modulationd) Velocity Modulation

And: Option d)

4. In Microwave we take the elements asa) Lumped circuit elementsb) Distributed circuit elementsc) Both a) and b)d) None of the above

Ans: Option b)

5. Short term fading in microwave communication links can be overcome bya) Increasing the transmitted powerb) Changing the antennac) Changing the modulation schemed) Diversity reception and transmission

Ans: Option d)

6. For handling large microwave power, the best medium isa) Coaxial lineb) Rectangular waveguidec) Striplined) Circular waveguide

Ans: Option b)

7. A Microwave tube amplifier uses an axial magnetic field and radial electric field. This is thea) Reflex Klystronb) Coaxial Magnetronc) Travelling wave magnetrond) CFA-Crossed Field Amplifier

Ans: Option d)

8. A disadvantage of microstrips with respect to stripline circuit is that the former:a) Do not let themselves to be printed-circuitsb) Are more likely to radiatec) Are bulkierd) Are more expensive and complex to manufacture

Ans: Option d)

9. Most of the power measuring microwave devices measurea) Average powerb) Peak powerc) Instantaneous powerd) None of these

Ans: Option a)

10. HEMT used in microwave circuit is aa) Sourceb) High power amplifierc) Detectord) Low noise Amplifier

Ans: Option d)

11. Ionospheric preparation is not possible for microwaves becausea) Microwaves will be fully absorbed by the ionospheric layersb) There will be an abrupt scattering in all directionsc) Microwave will penetrate through the ionospheric layersd) There will be dispersion of microwave energy

Ans: Option c)

12. A waveguide section in a microwave circuit will act as aa) Low-pass filterb) Band-pass filterc) High-pass filterd) Band-reject filter

Ans: Option c)

13. The biggest advantage of the TRAPATT diode over the IMPATT diode is itsa) Low noiseb) Higher efficiencyc) Ability to operate at higher frequenciesd) Lesser sensitivity to harmonics

Ans: Option b)

14. A varactor diode may not be useful at microwave frequenciesa) For electronic tuningb) for frequency multiplicationc) as an oscillatord) As a parametric amplifier

Ans: Option c)

15. The negative resistance in a tunnel diodea) is maximum at the peak point of the characteristicb) is available between the peak and valley pointsc) is maximum at valley pointd) may be improved by the use of reverse bias

Ans: Option b)

16. Which one of the following is a transferred electron device?a) BARITT diodeb) IMPATT diodec) Gunn dioded) Step recovery diode

Ans: Option c)

17. A PIN diode is suitable for use as aa) Microwave switchb) Microwave mixed diodec) Microwave detectord) None of these

Ans: Option a)

18. The semiconductor diode which can be used in switching circuits at microwave range isa) PIN diodeb) Tunnel diodec) Varactor dioded) Gunn diode

Ans: Option a)

19. Microwave antenna aperture efficiency depends ona) Feed Patternb) Antenna Aperturec) Surface lossesd) Low side lobe level

Ans: Option b)

20. The noise produced in a microwave tube due to random nature of emission and electron flow is calleda) Partition noiseb) Shot noisec) Johnson noised) Shannon noise

Ans: Option b)

21. A duplexer is useda) To couple two different antennas to a transmitter without mutual interferenceb) To allow one antenna to be used for reception or transmission without mutual interferencec) To prevent interference between two antennas when they are connected to a receiverd) To increase the speed of the pulses in pulsed radar

Ans: Option b)

22. One of the reasons why vacuum tubes eventually fail at microwave frequencies is that theira) Noise figure increasesb) Transit time becomes too shortc) Shunt capacitive reactances become too larged) Series inductive reactances become too small

Ans: Option a)

23.A magic-Tee is nothing buta) A modification of E-plane teeb) A modification of H-plane teec) A combination of E-Plane and H-Planed) Two E-plane tees connected in parallel

Ans: Option c)

24. Which of the following can be used for amplification of microwave energy?a) Travelling wave tubeb) Magnetronc) Reflex Klystrond) Gunn diode

Ans: Option a)

25. In microwave power measurements using bolometer, the principle of working is the variation ofa) Inductance with absorption of powerb) Resistance with absorption of powerc) Capacitance with absorption of powerd) Cavity dimensions with heat generated by the power

Ans: Option b)

26. In π mode operation of magnetron, the spokes due to phase focusing effect rotate at an angular velocity corresponding toa) One pole/cycleb) Two poles/cyclec) Four poles/cycled) Six poles/cycle

Ans: Option b)

27. For Gunn diodes, gallium arsenide is preferred to silicon because the formera) Has a suitable empty energy band, which silicon does not haveb) Has a higher ion mobilityc) Has a lower noise at the highest frequenciesd) Is capable of handling higher power densities

Ans: Option a)

28. For best low-level noise performance in the X-band an amplifier should usea) A bipolar transistorb) A Gunn diodec) A step recovery dioded) An IMPATT diode

Ans: Option c)

29. Travelling wave parametric amplifiers are used toa) provide a greater gainb) reduce the number of varactor diodes requiredc) avoid the need for coolingd) provide a greater bandwidth

Ans: Option d)

30. The major advantage of TWT over Klystrona) higher gainb) higher frequencyc) higher outputd) higher bandwidth

Ans: Option d)

31. Microwave frequency range extends froma) 3 MHz to 30 MHzb) 30 MHz to 300 MHzc) 300 MHz to 3000 MHzd) 500 MHz to 30000 MHz

Ans: Option d)

32. Due to curvature of earth, microwave repeaters are placed at a distance of abouta) 10 Kmb) 50 Kmc) 150 Kmd) 250 Km

Ans: Option b)

33. At microwave frequencies the size of the antenna becomesa) Very largeb) Largec) Smalld) Very Small

Ans: Option d)

34. Which of the following noise becomes important at microwave frequenciesa) Shot noiseb) Flicker noisec) Thermal noised) Transit time noise

Ans: Option d)

35. The phenomenon of microwave signals following the curvature of earth is known asa) Faraday effectb) Ductingc) Wave tiltd) Troposcatter

Ans: Option b)

36. The front end of an amplifier chain in manufacture of a communication system is kept immersed in liquid nitrogen toa) Dissipate heat generated by amplifierb) Expand the frequency responsec) Improve its noise figure

d) reduce the distortion by the amplifier

Ans: Option c)

37. In microwave communication links, the rain drop attenuation experienced is mainly due toa) Absorption of microwave energy by water vapourb) resonance absorption of atomic vibration in water moleculesc) scattering of microwaves by collection of water dropsd) refraction of microwaves through liquid-drop lenses formed by rain

Ans: Option a)