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ET1 SEP EXAM 2018 > NAVEDTRA 14183A, NAVY ELECTRICITY AND ELECTRONICS TRAINING SERIES, MODULE 11-MICROWAVE PRINCIPLES > Flashcards

NAVEDTRA 14183A, NAVY ELECTRICITY AND ELECTRONICS TRAINING SERIES, MODULE 11-MICROWAVE PRINCIPLES Flashcards

1
Q

The microwave region is that portion of the electromagnetic spectrum which falls between 1000 megahertz and what?

A

100,000 megahertz

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2
Q

What is microwave theory based on?

A

Electromagnetic fields

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3
Q

Which transmission media is more efficient than two-wire lines for transferring electromagnetic energy because the fields are completely confined by the conductors?

A

Coaxial lines

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4
Q

What is the most efficient way to transfer electromagnetic energy?

A

Waveguides

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5
Q

What is the primary lower-frequency limitation of waveguides?

A

Physical size

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6
Q

A waveguide may be considered as having upper and lower quarter-wave sections and a central section which is a solid conductor that is called what?

A

Bus bar

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7
Q

In practical applications, the wide dimension of a waveguide is usually what wavelength at the operating frequency?

A

0.7

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8
Q

Two conditions, known as what, must be satisfied for energy to travel through a waveguide?

A

Boundary conditions

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9
Q

When a quarter-wavelength probe is inserted into a waveguide and supplied with microwave energy, it will act as what type of antenna?

A

Quarter-wave vertical

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10
Q

Which type of frequency in a waveguide would cause angles of incidence and reflection to be zero degrees?

A

Cutoff frequency

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11
Q

What is the forward-progress velocity of the wavefront in a waveguide called that is somewhat slower than the speed of light?

A

Group velocity

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12
Q

The cutoff wavelength of a circular guide is how many times the diameter of the waveguide?

A

1.71

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13
Q

What are the three devices used to inject or remove energy from waveguides?

A

Probes, loops, and slots

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14
Q

Power losses are greater in what type of waveguide because the inner surfaces are not perfectly smooth?

A

Flexible

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15
Q

Permanent, semi-permanent, along with what else are the three basic types of waveguide joints?

A

Rotating

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16
Q

What provides good electromagnetic continuity between sections of waveguide with very little power loss?

A

Choke joint

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17
Q

Which electrical action takes place that causes very rapid corrosion of the metals when two dissimilar metals, such as copper and steel, are in direct contact?

A

Electrolysis

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18
Q

Which type of device provides a method of sampling energy from within a waveguide for measurement or use in another circuit?

A

Directional coupler

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19
Q

What is the upper frequency limit for a conventional resonant circuit?

A

2000-3000 MHz

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20
Q

What is any space completely enclosed by conducting walls that can contain oscillating electromagnetic fields and posses resonant properties?

A

Resonant cavity

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21
Q

Which two variables determine the primary frequency of any resonant cavity?

A

Physical size and shape

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22
Q

The resonant frequency of a cavity can be varied by changing any of three parameters: cavity volume, cavity capacitance, or what else?

A

Cavity inductance

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23
Q

What is it known as when you change the frequencies of a cavity?

A

Tuning

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24
Q

What are used to determine the frequency of the energy traveling in a waveguide?

A

Cavities

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25
Q

What is the most simple of the commonly used waveguide junctions?

A

T-Junction

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26
Q

Which two basic types are T junctions divided into?

A

E and H Type

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27
Q

What are the two most commonly used hybrid junctions?

A

Magic-T and Hybrid ring

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28
Q

What permits a system to use the same antenna for both transmitting and receiving?

A

Duplexer

29
Q

Which type of device is composed of material that causes it to have useful magnetic properties and, at the same time, high resistance to current flow?

A

Ferrite

30
Q

Which two basic types of motion do electrons have?

A

Orbital and Electron spin

31
Q

Which type of ferrite device can be constructed so that it allows microwave energy to pass in one direction but blocks energy in the other direction in a waveguide?

A

Isolator

32
Q

Which theory do tubes that are effiecient in the microwave range usually operate on?

A

Velocity modulation

33
Q

What is the time required called for electrons to travel from the cathode to the plate?

A

Transit time

34
Q

What can an electron be accelerated or decelerated by?

A

Electrostatic field

35
Q

What is defined as that variation in the velocity of a beam of electrons caused by the alternate speeding up and slowing down of the electrons in the beam?

A

Velocity modulation

36
Q

What are velocity-modulated tubes used in radar and communications equipment as oscillators and amplifiers?

A

Klystrons

37
Q

What absorb energy from the electron beam?

A

Catcher grids

38
Q

Klystron amplifiers have been built with as many as how many intermediate cavities in addition to the input and output cavities?

A

Five

39
Q

How many power sources are required for reflex klystron operation?

A

Three

40
Q

What is a unit that expresses the logarithmic ratio between the input and output of any given component, circuit, or system and may be expressed in terms of voltage, current, or power?

A

Bel

41
Q

Any figure expressed in bels can be easily converted to decibels by multiplying the figure by what?

A

10

42
Q

What are used to reduce a signal to a smaller level for use or measurement?

A

Attenuators

43
Q

Typically, what will a radar receiver be approximately rated at?

A

-107 dBm

44
Q

The Traveling Wave Tube is capable of gains greater than what with bandwidths exceeding an octave?

A

40 dB

45
Q

Traveling-wave tubes have been designed for frequencies as low as 300 megahertz and as high as what?

A

50 gigahertz

46
Q

What is a self-contained microwave oscillator that operates differently from the linear-beam tubes, such as the twt and the klystron?

A

Magnetron

47
Q

The force exerted on an electron in a magnetic field is at what type of angles to both the field and the path of the electron?

A

Right

48
Q

Which two classes are Magnetron oscillators divided into?

A

Negative-resistance and Electron-resonance

49
Q

Oscillations are sustained in a magnetron because as electrons pass through the AC and DC fields, they gain energy from the DC field and give up energy to the AC field. What are the electrons that give up energy to the AC field called?

A

Working electrons

50
Q

What is the cumulative action of many electrons returning to the cathode while others are moving toward the anode forms a pattern resembling the moving spokes of a wheel known as?

A

Space-Charge wheel

51
Q

By what means can energy (rf) be removed from a magnetron?

A

Coupling loop

52
Q

What consists of a metal ring inserted between the two rings of a double-strapped magnetron, which serves to increase the strap capacitance?

A

Cookie-cutter tuner

53
Q

Which type of broadband microwave amplifier can also be used as an oscillator?

A

Platinotron

54
Q

The bandwidth of the cfa, at any given instant, is approximately plus or minus what percent of the rated center frequency?

A

5

55
Q

What is a pn junction with a very high concentration of impurities in both the p and n regions?

A

Tunnel-Diode

56
Q

Tunnel-diode oscillators can be mechanically or electronically tuned over frequency ranges of about one octave and have what approximate top-end frequency limit?

A

10 GHz

57
Q

What is the most common type of microwave tunnel-diode amplifiers?

A

Reflection-type circulator-coupled

58
Q

What is a variable-capacitance, pn-junciton diode that makes good use of the voltage dependency of the depletion-area capacitance of the diode?

A

Varactor

59
Q

Which type of waveguide device allows energy to travel in only one direction?

A

Circulator

60
Q

The capacitance of a typical varactor can vary from 2 to 50 picofarads for a bias variation of just how many volts?

A

2

61
Q

What is the primary limitation on receiver sensitivity and is the name given to very small randomly fluctuating voltages that are always present in electronic circuits?

A

Electronic noise

62
Q

What is the typical gain of parametric amplifier?

A

20 dB

63
Q

Parametric frequency converters, using varactors, are how many basic types?

A

Three

64
Q

Bulk-effect semiconductors are of two basic types: transferred-electron and which other type?

A

Avalanche transit-time

65
Q

The discovery that microwaves could be generated by applying a steady voltage across a chip of n-type gallium-arsenide (GaAs) crystal was made in what year by J.B. Gunn?

A

1963

66
Q

Which source of microwave energy uses the bulk-effect, gallium-arsenide semiconductor?

A

Gunn oscillator

67
Q

The gunn oscillator can deliver continuous power up to about 65 milliwatts and pulsed outputs of up to how many watts peak?

A

200

68
Q

Point contact diodes, commonly called what, are the oldest microwave semiconductor devices?

A

Crystals

ET1 SEP EXAM 2018 (28 decks)

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