Module 11 - Microwave Principles
Navy Electricity and Electronics Training Series (NEETS)
Chapter 3:  Assignment 2 Pages 9 - 16

ASSIGNMENT 2

Textbook assignment: Chapter 2, "Microwave Principles," pages 2-1 through 2-66. Chapter 3, "Microwave Antennas," pages 3-1 through 3-20.

2-1. As the frequency in a conventional vacuum tube is increased, what is the effect on the capacitive reactance of the tube?

1. It increases

2. It decreases

3. It remains the same

2-2. Undesirable degenerative feedback in conventional vacuum tubes can be caused by which of the following tube factors?

1. Grid bias

2. Transit time

3. Plate voltage

4. Lead inductance

2-3. a decrease in efficiency in a conventional vacuum tube caused by a phase shift between plate current and grid voltage can be the result of excessive

1. transit time

2. lead inductance

3. capacitive reactance

4. interelectrode capacitance

2-4. Moving tube electrodes further apart to decrease interelectrode capacitance causes which of the following tube characteristics to increase?

1. Transit time

2. Lead inductance

3. Inductive reactance

4. Capacitive reactance

2-5. Which of the following properties of an electron is directly proportional to its velocity?

1. Mass

2. Kinetic energy

3. Potential energy

4. All of the above

2-6. An electron that enters an electrostatic field and travels in the same direction as the lines of force will react in what way?

1. It will accelerate

2. It will decelerate

3. It will spin faster

4. It will spin slower

2-7. The alternate speeding up and slowing down of electrons in a beam that produces electron bunches is known as which of the following modulation terms?

1. Carrier modulation

2. Velocity modulation

3. Amplitude modulation

4. Frequency modulation

2-8. How is an electron affected, if at all, if it enters the buncher-grid gap when the potential across the grids is positive?

1. It is deflected

2. It is accelerated

3. It is decelerated

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2-9. The point in a stream of electron bunches at which the catcher cavity will most efficiently remove power is determined by which of the following factors?

1. Electron spin velocity

2. The size of the cavity

3. The size of the bunches

4. Frequency of the buncher-grid signal

2-10. Which of the following electronic interactions is used in klystron operation?

1. Velocity-modulation

2. Voltage and current

3. Variable-capacitance

4. Crossed electromagnetic-field

2-11. In a klystron, an ac potential is superimposed on the dc voltage that is applied to the buncher grids by what component?

1. The cathode

2. The accelerator grid

3. The buncher-grid cavity resonator

4. The catcher-grid cavity resonator

2-12. a two-cavity klystron that has a feedback path from the catcher cavity to the buncher cavity will operate as what type of circuit?

1. Modulator

2. Amplifier

3. Oscillator

4. Discriminator

2-13. The input signal to a two-cavity klystron amplifier is applied to which of the following components?

1. The cathode

2. The catcher grids

3. The buncher grids

4. The accelerator grid

2-14. In a klystron, the placement of additional cavities between the buncher cavity and catcher cavity increases the power output by causing which of the following electronic actions?

1. Increased velocity modulation

2. Decreased velocity modulation

3. Increased electron-beam speed

4. Decreased electron-beam speed

2-15. What is the purpose of applying a large negative pulse to the cathode of a three- cavity klystron?

1. To focus the electron beam

2. To accelerate the electron beam

3. To decelerate the electron beam

4. To modulate the electron beam

2-16. In a three-cavity klystron, what cavity, if any, contributes most to the velocity modulation of the electron beam?

1. The middle cavity

2. The catcher cavity

3. The buncher cavity

4. None

2-17. The bandwidth of a multicavity klystron can be increased by using which of the following tuning methods?

1. Varactor tuning

2. Staggered tuning

3. Electronic tuning

4. Synchronous tuning

2-18. The repeller of a reflex klystron replaces what component in other types of klystrons?

1. The input cavity

2. The output cavity

3. The buncher cavity

4. The intermediate cavity

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2-19. In a reflex klystron, what type(s) of electrical charge, if any, does the repeller have?

1. Positive only

2. Negative only

3. Alternately positive and negative

4. None

2-20. In a reflex klystron, the length of time a constant speed electron remains in the space separating the grid and repeller is determined by which of the following factor(s)?

1. Repeller voltage

2. Electron velocity

3. Both 1 and 2 above

4. The distance between grid and repeller

2-21. a reflex klystron in which the constant- speed electrons remain in the repeller field for 3/4 cycle is operating in what mode?

1. Mode 1

2. Mode 2

3. Mode 3

4. Mode 4

2-22. In a reflex klystron, the choice of operating mode is determined by which of the following circuit factors?

1. The voltage required

2. The power available

3. The frequency range available

4. Both 2 and 3 above

2-23. In the higher modes, power and amplitude limitations in a reflex klystron are caused by which of the following actions?

1. Electron debunching

2. Frequency fluctuation

3. Decreasing transit time

4. Increasing electron density

2-24. The term "bel" is a unit of measurement that expresses which of the following relationships?

1. Ratio of voltage and resistance

2. Logarithmic ratio between input and output

3. Geometric progression from input to output

4. Ratio of voltage to current

2-25. The term "dBm" is based on what standard reference level?

1. 1 watt

2. 1 volt

3. 1 milliwatt

4. 1 millivolt

2-26. Which of the following TWT characteristics makes it ideal for use as an RF amplifier?

1. High-noise and narrow-bandwidth

2. Low-noise and wide-bandwidth

3. High-noise and wide-bandwidth

4. Low-noise and narrow-bandwidth

2-27. In a TWT, what is the primary purpose of the helix?

1. To increase the forward velocity of the input

2. To decrease the forward velocity of the input

3. To decrease the reflected velocity of the output

4. To increase the reflected velocity of the output

2-28. Velocity modulation of the electron beam in a TWT is achieved by what action?

1. By the action of resonant cavities

2. By interaction of the electron beam with the permanent magnet field 3. By interaction of the electron beam with the electric field in the helix

4. All of the above

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2-29. In a TWT, what is the purpose of the attenuators along the helix?

1. To focus the beam

2. To limit the input

3. To limit the output

4. To prevent reflections

2-30. a microwave tube that extracts energy from a wave that travels from the collector toward the cathode is referred to as the

1. klystron

2. traveling-wave tube

3. crossed-field amplifier

4. backward-wave oscillator

2-31. In a magnetron, the magnetic field between the plate and cathode serves what purpose?

1. Acts as a grid

2. Provides a plate load

3. Acts as a space-charge suppressor

4. Provides filament power

2-32. What property in a magnetron is controlled by the cavities in the plate?

1. Input power

2. Output power

3. Input voltage

4. Output frequency

2-33. In a magnetron, what causes the path of an electron to curve when it is moving from the cathode to the plate?

1. The cathode pulse

2. The electric field

3. The resonant cavities

4. The permanent magnetic field

2-34. The critical value of magnetic field strength in a magnetron causes which of the following electronic actions?

1. Plate cavities stop oscillating

2. Output power decreases to zero

3. Electrons strike the plate and return to the cathode

4. Electrons miss the plate and return to the cathode

2-35. Magnetron oscillators are divided into what total number of classes?

1. One

2. Two

3. Three

4. Four

2-36. THIs QUESTION HAS BEEN DELETED.

2-37. In a negative-resistance magnetron, which, if any, of the following values of magnetic field strengths is required to start oscillations?

1. Critical value

2. Slightly lower than critical value

3. Slightly higher than critical value

4. None of the above

2-38. In magnetrons, the effect of filament bombardment can be reduced by which of the following actions?

1. Increasing plate voltage

2. Reducing filament voltage

3. Reducing signal frequency

4. Increasing signal frequency

2-39. In electron-resonance magnetrons, which of the following anode blocks is/are used?

1. Vane anode

2. Rising-sun anode

3. Hole-and-slot anode

4. Each of the above

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2-40. In the electron-resonance magnetron, the total electric field is produced by which of the following field combinations?

1. The dc field only

2. The ac and dc fields

3. The ac and magnetic fields

4. The dc and magnetic fields

2-41. Energy from working electrons is received by which of the following magnetron fields?

1. The ac field only

2. The dc field only

3. Both the ac and dc fields

4. The magnetic field

2-42. In a magnetron, the total action of many electrons returning to the cathode while others are moving toward the anode forms which of the following patterns?

1. Vertical wavefront

2. Space-charge wheel

3. Spherical wavefront

4. Horizontal space charge

2-43. The greatest power output is produced in what magnetron mode of operation?

1. Mode 1

2. Mode 2

3. The pi mode

4. The radian mode

2-44. Magnetic lines of force passing between cavities are intercepted in which, if any, of the following magnetron coupling methods?

1. Slot coupling method

2. Strap-fed loop method

3. Segment-fed loop method

4. None of the above

2-45. Inductive tuning in a magnetron is accomplished by which of the following actions?

1. Changing the cavity resistance

2. Altering the cavity surface-to-volume ratio

3. Decreasing the size of the slot gap

4. Decreasing the space charge

2-46. a magnetron should be "baked in" under which of the following conditions?

1. Before each use

2. After periods of idleness

3. After initial installation

4. Both 2 and 3 above

2-47. The crossed-field amplifier produces which of the following desirable circuit characteristics?

1. Wide bandwidth

2. High efficiency

3. Large power-handling capability

4. All of the above

2-48. The tunneling action of the tunnel diode produces which of the following useful properties?

1. Long transit time

2. Positive resistance

3. Negative resistance

4. Variable inductance

2-49. The tuned circuit in a tunnel-diode oscillator determines which of the following circuit values?

1. Frequency

2. Resistance

3. Power range

4. Capacitance

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2-50. Tuning a tunnel-diode oscillator by changing the capacitance of the tuned circuit can be accomplished by which of the following tuning methods?

1. Bias tuning

2. Slot tuning

3. Current tuning

4. Varactor tuning

2-51. In the reflection-type, circulator-coupled tunnel-diode amplifier, what component prevents feedback to the tuned input circuit?

1. The circulator

2. The output loop

3. The tuned cavity

4. The tunnel diode

2-52. Stability is a problem in which, if any, of the following tunnel-diode frequency converters?

1. High-gain converter

2. Unity-gain converter

3. Conversion-loss converter

4. None of the above

2-53. The varactor is a type of PN junction that acts as which of the following types of electronic devices?

1. Fixed resistor

2. Fixed capacitor

3. Variable resistor

4. Variable capacitor

2-54. What is the most important feature of the parametric amplifier?

1. Low noise

2. High gain

3. Power output

4. Frequency range

Figure 2A. - Voltage amplification circuit.

IN ANSWERING QUESTION 2-55, REFER to FIGURE 2A.

2-55. How is amplification accomplished in the circuit?

1. By opening the switch

2. By varying the frequency

3. By varying the resistance

4. By varying the capacitance

2-56. In a nondegenerative parametric amplifier, how does the pump frequency compare to the input signal frequency?

1. The pump frequency is half the input signal frequency

2. The pump frequency is double the input signal frequency

3. The pump frequency is more than double the input signal

4. The pump frequency is equal to the input signal frequency

2-57. In a nondegenerative parametric amplifier with a pump frequency of 12 gigahertz and an idler frequency of 9 gigahertz, what is the input signal frequency?

1. 3 gigahertz

2. 18 gigahertz

3. 21 gigahertz

4. 108 gigahertz

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2-58. Bulk-effect semiconductors have what primary advantage over normal pn- junction semiconductors?

1. Smaller size

2. Lower frequency

3. Simpler construction

4. Greater power output

2-59. Gallium-arsenide semiconductors begin to exhibit which of the following electrical characteristics at the threshold point? 1. Variable inductance

2. Positive resistance

3. Negative resistance

4. Variable capacitance

2-60. In an avalanche transit-time diode, what causes the dc bias energy previously absorbed by avalanche electrons to be given up to the microwave field?

1. The electron velocity

2. The negative-resistance property

3. The electron transit time

4. The amount of dc bias energy available

2-61. In a point-contact diode, passing a large current from the catwhisker to the silicon crystal produces what region?

1. a domain region

2. a small p region

3. a small n region

4. An avalanche region

2-62. a Schottky barrier diode has which of the following advantages over a point- contact diode?

1. Lower frequency range

2. Higher frequency range

3. Lower noise generation

4. Higher noise generation

2-63. The PIN diode begins acting as a variable resistance at what minimum frequency?

1. 100 megahertz

2. 200 megahertz

3. 300 megahertz

4. 400 megahertz

2-64. Power ratio is a term used to express what property of an antenna?

1. Efficiency

2. Reciprocity

3. Sensitivity

4. Power output

2-65. a standing-wave ratio (SWR) describes which of the following quantities?

1. Transmission-to-reception efficiency value

2. The amount of output power

3. The amount of mismatch between a transmission line and its load

4. The amount of characteristic

impedance

2-66. Directivity refers to which of the following properties of a radiated beam?

1. Power gain

2. Standing-wave ratio

3. Narrowness of the beam

4. Polarization of the beam

2-67. Surface angular measurements for antenna directivity in radar and communications systems are made in relationship to which of the following references?

1. Vertical plane only

2. Horizontal plane only

3. Horizontal plane and true north

4. Vertical plane and true north

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2-68. Radar range is determined as a function of which of the following measures?

1. Pulse travel time

2. Elevation angle of the antenna

3. Distance to the horizon

4. Angular velocity of the energy

2-69. The parabolic reflector is often used because it produces a radiation pattern with which of the following antenna characteristics?

1. Omnidirectional

2. Highly directive

3. Many equal lobes

4. Spherical wavefronts

2-70. In a lens antenna, what is the purpose of the collimating lens?

1. It produces spherical wavefronts

2. It produces an omnidirectional pattern

3. It forces parallel segments of the wavefront into spherical paths

4. It forces radial segments of the wavefront into parallel paths

2-71. a lens antenna which accelerates some portion of the wavefronts so that all wavefronts exit the lens at the same time is referred to as the

1. metallic delay lens

2. waveguide-type lens

3. loaded microwave lens

4. dielectric delay lens

2-72. In a delay-type lens, the amount of delay in the phase of the wave passing through the lens is determined by which of the following characteristics?

1. The dielectric constant of the lens

2. The characteristic impedance of the lens

3. The physical size of the lens

4. All of the above

2-73. What is/are the basic type(s) of antenna array(s) in common use?

1. Driven only

2. Parasitic only

3. Parasitic and driven

2-74. In a frequency-sensitive antenna, the physical length of the serpentine section and its relationship to the wavelength of the applied energy determines which of the following characteristics?

1. Output power

2. Beam narrowness

3. Antenna efficiency

4. Direction of the beam

2-75. In a horizontal-slot antenna, the polarization of the energy is radiated in what direction?

1. Vertical

2. Spherical

3. Horizontal

4. Omnidirectional

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