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ECE 4C > Antenna > Flashcards

Antenna Flashcards

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
These waves radiate outwards from the source at the speed of light, 300 million meters per second.
Propagation
26
______ and ______ are both EM waves, differing only in frequency and wavelength.
Light waves (waves we see) and radio waves (waves we hear)
27
EM waves travel in ______ unless acted upon by some outside force
straight lines
28
As EM waves spread out from the point of origin, they decrease in strength in what is described as an
inverse square relationship
29
a type of receiver that transmits signals over many billions of kilometres from outer space with only 25 W of power
Voyager 2
30
A radio signal is called an _______ because it is made up of both electric and magnetic field.
electromagnetic wave
31
Whenever voltage is applied to the antenna, an an ________ is set up.
electric field
32
when a voltage causes current to flow in the antenna, ____ is produced
magnetic field
33
these two are at right angles to each other and the direction of propagation is at right angles to both fields.
electric and magnetic field
34
is an invisible force field created by a magnet.
magnetic field
35
is generated around a conductor when current flows through it.
magnetic field
36
The strength and direction of the magnetic field depend upon __________ and _________ of the current flow.
the magnitude and direction
37
The SI unit for magnetic field strength is
ampere-turns per meter
38
an invisible force field produced by the presence of a potential difference between two conductors
electric field
39
exists between any two points across which a potential difference exists
electric field
40
The SI unit for electric field strength is
volts per meter
41
is the dielectric constant of the material between the two conductors
Permittivity
42
two types of waves
transverse and longitudinal
43
type of wave in which vibration is from side to side; that is, at right angles to the direction in which they travel
Transverse wave
44
type of wave in which vibration is parallel to the direction of propagation
longitudinal
45
The energy level of the signal _________ rapidly with distance from the transmitting antenna
decreases
46
The angle of reflection is equal to the angle of __________
incidence
47
it is the bending of a wave due to the physical makeup of the medium through which the wave passes
diffraction
48
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
index of refraction
49
The relationship between the angles and the indices of refraction is given by a formula known as __________
Snell’s law
50
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
Huygen’s principle
51
propagation is strongest at the low- and medium-frequency ranges
Ground wave or surface wave
52
The _________ must be vertically polarized to propagate from an antenna
ground wave or surface wave
53
radio waves that travel or progress along the surface of the earth
ground waves or surface waves
54
what type of broadcast signals are propagated primarily by ground waves during the day & by sky waves at night?
AM broadcast signals
55
Are radio waves that are radiated by the antenna into the upper atmosphere, where they are bent back to earth
sky wave or isotropic wave
56
When a radio signal goes into the _______, the different levels of ionization cause the radio waves to be gradually bent
ionosphere
57
is the propagation of radio waves bent (refracted) back to the Earth's surface by the ionosphere
sky wave or isotropic wave
58
_____ frequency is a result of skywave propagation
HF radio communication (3 and 30 MHz)
59
it is also known as Line of Sight or direct wave
space wave
60
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
space wave, light of sight, direct wave
61
travel directly from one antenna to another without reflection on the ground
space wave, light of sight, direct wave
62
Occurs when both antennas are w/in LOS of each other
space wave, light of sight, direct wave
63
It is the lowest of the atmosphere where all weather disturbances take place
troposphere
64
It is a region directly above the troposphere where no weather is seen but circulation does occur
stratosphere
65
It is the region in the atmosphere above the stratosphere where the several ionized layers of low-density gas is found
ionosphere
66
The F layer combines into one layer at ____
night
67
whenever a voltage is applied to an antenna, _____ is set up.
Electric field
68
electric field causes current to flow in an antenna, which causes ______ to exist
magnetic field
69
The power transmitted by an antenna is always ______ (lesser/greater) than the power entering the transmitter.
lesser (because the antenna is a passive device)
70
Antenna achieves gain by _____
concentrating energy
71
It is the portion of an antenna's input impedance that is caused by the power radiated to space
Radiation Resistance
72
Radiated resistance dissipates power as
electromagnetic energy
73
This region is directly around the antenna and the electric and magnetic fields are distinguished
near field
74
In this region, electric and magnetic fields are separated (not radio waves) however, they still carry information to be transmitted
near field
75
The far-field region is ______ away from the antenna
ten wavelengths
76
This angle is the vertical angle measured upward of the ground plane
Angle of elevation
77
far-field is also called the ________
Fraunhofer zone
78
the most common applications of near-field
Radio Frequency Identification (RFID) and NearField Communication (NFC)
79
Most wireless communication uses ________ field
near field
80
refers to the orientation of magnetic and electric fields with respect to the earth.
Polarization
81
This polarization shows that electric and magnetic fields rotate as they leave the antenna.
Circular polarization
82
This device is used so that an antenna can receive and transmit energy
diplexer
83
at low to medium frequencies, radio waves follow the curvature of the earth.
Groundwave propagation Surface wave propagation
84
Surface wave propagation is strongest at what frequency range
Low to medium-frequency
85
What signals are commonly propagated in Groundwave propagation?
AM broadcast signals
86
At what frequency the earth start to attenuate the signal?
Frequencies >3MHz
87
It is the uppermost part of the atmosphere
Ionosphere
88
It is the conversion of atoms or molecules into an ion by light (heating or charging) from the sun in the atmosphere
Ionization
89
It creates a set of stratum where each has a peak density and a definable width or profile that influences radio propagation
Ionization
90
This layer is responsible for most skywave propagation
F layer
91
This is the thickest layer
F layer
92
the other term for E layer
Kennelly Heaviside layer
93

ECE 4C (5 decks)

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