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ECE 4C > Antenna > Flashcards

Antenna Flashcards

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1
Q

a transducer that converts radio
frequency of electric current to electromagnetic waves
that are radiated into space

A

Antenna

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2
Q

Antenna is a _____ type of communication

A

simplex

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3
Q

An antenna is a/an (passive, active) device

A

passive

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4
Q

This states that the receive and transmit properties of an antenna are identical

A

Reciprocity

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5
Q

It is a conductor or a system that radiates or intercepts electromagnetic wave energy

A

Antenna

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6
Q

It converts electric signals to electromagnetic waves for transmission or reception through air or space

A

Antenna

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7
Q

An antenna is a type of ____magnet

A

electromagnet

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8
Q

a hypothetical antenna having the same radiation in all directions

A

Isotropic antenna

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9
Q

What is the field strength of an isotropic antenna?

A

Same in all directions

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10
Q

Graphical representation of radiation properties of an antenna

A

Radiation Pattern

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11
Q

It is the measure of the directivity of an antenna

A

Beamwidth

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12
Q

The maximum radiation intensity produced by the antenna is compared to that produced by a lossless isotropic radiator supplied with the same level of power.

A

Antenna Gain

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13
Q

The measure of the antenna’s maximum radiation intensity in a stated direction to the maximum radiation intensity of a reference antenna with identical power applied to it

A

Antenna Power Gain

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14
Q

The ratio of radiation intensity in a particular direction to the average radiated power

A

Antenna Directive Gain

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15
Q

Relationship between antenna gain and effective area

A

Antenna Gain

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16
Q

Defined as the orientation of the electric field(E-plane) of an electromagnetic wave

A

Polarization

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17
Q

The sense of the wave radiated by an antenna

A

Polarization

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18
Q

Type of polarization in which the direction of the electric field is parallel to the earth

A

Horizontal

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19
Q

the direction of _______ specifies the polarization of the antenna

A

Electric Field

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20
Q

type of polarization in which the electric field is perpendicular to the Earth’s surface

A

Vertical

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21
Q

Types of polarization in which the wave radiates energy in both the horizontal and vertical planes and all planes in between

A

Circular

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22
Q

The ideal or standard antenna

A

Isotropic

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23
Q

How radio waves travel from point A to point B;
and the events occurring in the transmission
the path that affects the communication between
the points, stations, or operators.

A

Propagation

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24
Q

When the electrons in a conductor are made to oscillate back and forth _________are produced.

A

Electromagnetic Waves (EM waves)

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25
Q

These waves radiate outwards from the source at
the speed of light, 300 million meters per second.

A

Propagation

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26
Q

______ and ______ are both EM waves, differing only
in frequency and wavelength.

A

Light waves (waves we see) and radio waves
(waves we hear)

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27
Q

EM waves travel in ______ unless acted
upon by some outside force

A

straight lines

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28
Q

As EM waves spread out from the point of origin,
they decrease in strength in what is described as an

A

inverse square relationship

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29
Q

a type of receiver that transmits signals over many billions of kilometres from outer space with only 25 W of power

A

Voyager 2

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30
Q

A radio signal is called an _______
because it is made up of both electric and magnetic
field.

A

electromagnetic wave

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31
Q

Whenever voltage is applied to the antenna, an
an ________ is set up.

A

electric field

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32
Q

when a voltage causes current to flow in the antenna, ____ is produced

A

magnetic field

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33
Q

these two are at right angles to each
other and the direction of propagation is at
right angles to both fields.

A

electric and magnetic field

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34
Q

is an invisible force field created
by a magnet.

A

magnetic field

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35
Q

is generated around a conductor when current flows through it.

A

magnetic field

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36
Q

The strength and direction of the magnetic field
depend upon __________ and _________ of the
current flow.

A

the magnitude and direction

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37
Q

The SI unit for magnetic field strength is

A

ampere-turns per meter

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38
Q

an invisible force field
produced by the presence of a potential
difference between two conductors

A

electric field

39
Q

exists between any two points
across which a potential difference exists

A

electric field

40
Q

The SI unit for electric field strength is

A

volts per meter

41
Q

is the dielectric constant of the material between the two
conductors

A

Permittivity

42
Q

two types of waves

A

transverse and longitudinal

43
Q

type of wave in which vibration is from side to side; that is, at right angles to the direction in which they travel

A

Transverse wave

44
Q

type of wave in which vibration is parallel to the direction of propagation

A

longitudinal

45
Q

The energy level of the signal _________ rapidly
with distance from the transmitting antenna

A

decreases

46
Q

The angle of reflection is equal to the angle of
__________

A

incidence

47
Q

it is the bending of a wave due to the physical makeup of the medium through which the wave passes

A

diffraction

48
Q

The _______ is obtained by dividing the speed of a light (or radio) wave in a vacuum and the speed of a light (or radio) wave in the medium that causes the wave to be bent

A

index of refraction

49
Q

The relationship between the angles and the
indices of refraction is given by a formula
known as __________

A

Snell’s law

50
Q

Assuming that all electromagnetic waves radiate
as spherical waveforms from a source, each
point on a wavefront can be considered as a
point source for additional spherical waves

A

Huygen’s principle

51
Q

propagation is strongest at the low- and
medium-frequency ranges

A

Ground wave or surface wave

52
Q

The _________ must be vertically polarized to propagate from an antenna

A

ground wave or surface wave

53
Q

radio waves that travel or progress along the surface of the earth

A

ground waves or surface waves

54
Q

what type of broadcast signals are propagated primarily by
ground waves during the day & by sky waves at night?

A

AM broadcast signals

55
Q

Are radio waves that are radiated by the
antenna into the upper atmosphere,
where they are bent back to earth

A

sky wave or isotropic wave

56
Q

When a radio signal goes into the _______, the different levels of ionization cause the radio waves to be gradually bent

A

ionosphere

57
Q

is the propagation of radio waves bent (refracted) back to the Earth’s surface by the ionosphere

A

sky wave or isotropic wave

58
Q

_____ frequency is a result of skywave propagation

A

HF radio communication (3 and 30 MHz)

59
Q

it is also known as Line of Sight or direct wave

A

space wave

60
Q

the propagation of waves travelling in a straight line.  These waves are deviated (reflected) by obstructions and cannot travel over the horizon or behind obstacles

A

space wave, light of sight, direct wave

61
Q

travel directly from one antenna to another without
reflection on the ground

A

space wave, light of sight, direct wave

62
Q

Occurs when both antennas are w/in LOS of each other

A

space wave, light of sight, direct wave

63
Q

It is the lowest of the atmosphere where all
weather disturbances take place

A

troposphere

64
Q

It is a region directly above the troposphere where no weather is seen but circulation does occur

A

stratosphere

65
Q

It is the region in the atmosphere above the
stratosphere where the several ionized layers of
low-density gas is found

A

ionosphere

66
Q

The F layer combines into one layer at ____

A

night

67
Q

whenever a voltage is applied to an antenna, _____ is set up.

A

Electric field

68
Q

electric field causes current to flow in an antenna, which causes ______ to exist

A

magnetic field

69
Q

The power transmitted by an antenna is always ______ (lesser/greater) than the power entering the transmitter.

A

lesser (because the antenna is a passive device)

70
Q

Antenna achieves gain by _____

A

concentrating energy

71
Q

It is the portion of an antenna’s input impedance that is caused by the power radiated to space

A

Radiation Resistance

72
Q

Radiated resistance dissipates power as

A

electromagnetic energy

73
Q

This region is directly around the antenna and the electric and magnetic fields are distinguished

A

near field

74
Q

In this region, electric and magnetic fields are separated (not radio waves) however, they still carry information to be transmitted

A

near field

75
Q

The far-field region is ______ away from the antenna

A

ten wavelengths

76
Q

This angle is the vertical angle measured upward of the ground plane

A

Angle of elevation

77
Q

far-field is also called the ________

A

Fraunhofer zone

78
Q

the most common applications of near-field

A

Radio Frequency Identification (RFID) and NearField Communication (NFC)

79
Q

Most wireless communication uses ________ field

A

near field

80
Q

refers to the orientation of magnetic and electric fields
with respect to the earth.

A

Polarization

81
Q

This polarization shows that electric and magnetic fields rotate as they leave the antenna.

A

Circular polarization

82
Q

This device is used so that an antenna can receive and transmit energy

A

diplexer

83
Q

at low to medium frequencies, radio waves follow the curvature of the earth.

A

Groundwave propagation
Surface wave propagation

84
Q

Surface wave propagation is strongest at what frequency range

A

Low to medium-frequency

85
Q

What signals are commonly propagated in Groundwave propagation?

A

AM broadcast signals

86
Q

At what frequency the earth start to attenuate the signal?

A

Frequencies >3MHz

87
Q

It is the uppermost part of the atmosphere

A

Ionosphere

88
Q

It is the conversion of atoms or molecules into an ion by light (heating or charging) from the sun in the atmosphere

A

Ionization

89
Q

It creates a set of stratum where each has a peak density and a definable width or profile that influences radio propagation

A

Ionization

90
Q

This layer is responsible for most skywave propagation

A

F layer

91
Q

This is the thickest layer

A

F layer

92
Q

the other term for E layer

A

Kennelly Heaviside layer

93
Q
A

ECE 4C (5 decks)

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