Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

COMMS > ANTENNAS -2 > Flashcards

ANTENNAS -2 Flashcards

1
Q

A metallic conductor system capable of radiating and capturing electromagnetic energy

A

Antenna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Couples energy from a transmitter to an antenna or

from antenna to a receiver

A

Transmission Lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

A special type of transmission line that consists of a
conducting metallic tube through which high-frequency
electromagnetic energy is propagated

A

Waveguide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Electrical energy that has escaped into free space in the

form of transverse electromagnetic waves

A

Radio Waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The plane parallel to the mutually perpendicular lines of

the electric and magnetic fields.

A

Wavefront

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The ratio of radiated to reflected energy

A

Radiation Efficiency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Antenna wherein two conductors are spread out in a straight line to a total length of one quarter wavelength.

A

Quarter Wave Antenna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Another name for quarter wave antenna.

A

Vertical Monopole or Marconi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A half-wave dipole

A

Hertz Antenna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

A special coupling device that can be used to

direct the transmit and receive signals and provide the necessary isolation

A

Diplexer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

A polar diagram or graph representing field strengths or power densities at various angular positions relative to an antenna.

A

Radiation Pattern

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Radiation pattern plotted in terms of electric field

strength or power density

A

Absolute Radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Radiation pattern plots field strength or power density

with respect to the value at a reference

A

Relative Radiation Pattern

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The primary beam of an antenna.

A

Major lobe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The major lobes that propagates and receive

the most energy.

A

Front Lobe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Lobes adjacent to the front lobe.

A

Side lobes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The secondary beam of an antenna.

A

Minor Lobes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Lobes in a direction exactly opposite the front lobe

A

Back Lobe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The ratio of the front lobe power to the back lobe

power.

A

Front to Back Ratio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

The ratio of the front lobe to a side lobe.

A

Front to Side Ratio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

The line bisecting the major lobe; or pointing from
the center of the antenna in the direction of maximum
radiation.

A

Line of Shoot or Point

of Shoot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Antenna that radiates energy equally in all directions

A

Omni-directional Antenna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

The primary beam of an antenna.

A

Major Lobes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Radiates power at a constant rate uniformly in all

directions.

A

Isotropic Radiator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
The direction in which an antenna is always pointing.
Maximum Radiation
26
It is defined as an equivalent transmit power. It stands | for Effective Isotropic Radiated Power.
EIRP
27
The equivalent power that an isotropic antenna would have to radiate to achieve the same power density in the chosen direction at a given point as another antenna.
Effective Radiated Power (ERP) or (EIRP)
28
The power density in space and the actual power that a receive antenna produces at its output terminals.
Captured Power Density
29
It describe the reception properties of an antenna
Capture Area
30
Another name for capture area
Effective Area
31
The relationship of captured power to the received power density and the effective capture area of the received antenna.
Directly Proportional
32
It refers to the orientation of the electric field radiated | from the antenna.
Polarization
33
The angular separation between the two half-power (-3dB) points on the major lobe of an antenna's plane radiation pattern.
Antenna Beamwidth
34
The frequency range over which antenna operation is satisfactory.
Antenna Bandwidth
35
Another name for antenna input terminal
Feedpoint
36
The feedpoint presents an ac load to the transmission | line.
Antenna Input Impedance
37
``` The simplest type of antenna. Another names for elementary doublet ? Short Dipole; ? Elementary Dipole ? Hertzian Dipole ```
Elementary Doublet
38
Any dipole that is less than one-tenth wavelength
Electrically Short
39
Hertz antenna is name after him and he was the first to demonstrate the existence of electromagnetic waves.
Heinrich Hertz
40
A single pole antenna one quarter wavelength long; mounted vertically with the lower end either connected directly to ground or grounded through the antenna coupling network.
Marconi Antenna
41
Main disadvantage of Marconi Antenna.
Must be close | to the Ground
42
A technique use to increase the electrical length of | an antenna
Loading
43
A coil added in series with a dipole antenna which | effectively increases antenna's electrical length.
Loading Coil
44
A loading coil approximately increases the radiation resistance of the antenna
5 Ohms
45
``` An individual radiator; such as a half or quarter wave dipole. Two types of antenna elements ? Driven ? Parasitic Two Elements of a single antenna ? Two Wire ? Folded Dipole ```
Antenna Element
46
Its purpose is to increase the directivity and concentrate | the radiated power within a smaller geographic area.
Array
47
Elements that are directly connected to the transmission | line and receive power from the source.
Driven
48
Elements are not connected to the transmission line; they receive energy only through mutual induction with a driven element.
Parasitic
49
parasitic element that is shorter that its associated | driven element.
Director
50
Radiation pattern depends on the relative phase of feeds.
Driven
51
The simplest type of antenna arrays
Broadside Arrays
52
A widely used antenna commonly uses a folded dipole as the driven element and named after two Japanese scientists.
Yagi Uda
53
Typical directivity of a yagi-uda antenna.
7 dB and 9 dB
54
Formed by placing two dipoles at right angles to each other.
Turnstile Antenna
55
A class of frequency-independent antennas.
Log Periodic
56
A broadband VHF or UHF antenna that is ideally suited for applications for which radiating circular rather than horizontal or vertical polarized electromagnetic waves are required. Modes of propagation: ? Normal ? Axial
Helical Antenna
57
``` Antennas having half power beamwidths on the order of 1o or less. Three important characteristics: ? Front-to Back Ratio; ? Side-toSide Coupling ? Back-to-Back Coupling ```
Microwave Antenna
58
Antenna that provides extremely high gain and directivity and are very popular for microwave and satellite communications link. Two main part ? Parabolic Reflector ? Feed Mechanism
Parabolic Reflector Antenna
59
The effective area in a receiving parabolic antenna | and is always less than the actual mouth area.
Capture Area
60
The most commonly used transmission | line is a
Coax
61
A receiver-transmitter station used to increase the communications range of VHF; UHF; and microwave signals is called a(n)
Repeater
62
Microwave signals propagate by way of | the
Direct wave
63
The type of radio wave responsible for long-distance communications by multiple skips is the
Skywave
64
The ionosphere has its greatest effect | on signals in what frequency range?
3 to 30 MHz
65
The ionosphere causes radio signals to | be
refracted
66
Ground-wave communications is most | effective in what frequency range
300 kHz to 3 MHz
67
A wide-bandwidth multielement driven | array is the
Log-periodic
68
antenna has a unidirectional | radiation pattern and gain
Yagi
69
The radiation pattern of collinear and | broadside antennas
Bidirectional
70
Conductors in multielement antennas that do not receive energy directly from the transmission line are known as
Parasitic elements
71
In a Yagi antenna; maximum direction of | radiation is toward the
Director
72
The horizontal radiation pattern of a | vertical dipole is
circle
73
A direction antenna with two or more | elements is known as a(n)
Array
74
The impedance of a dipole is about
73 
75
The horizontal radiation pattern of a | dipole is a
figure of 8
76
An antenna that transmits or receives | equally well in all directions is said to be
Omnidirectional
77
The magnetic field of an antenna is perpendicular to the earth. The antenna’s polarization
is horizontal
78
A popular vertical antenna is the
Ground plane
79
A popular half-wavelength antenna is | the
Dipole
80
A shorted half-wave line at the operating | frequency acts like a(n)
Series Resonant Circuit
81
A shorted quarter-wave line at the | operating frequency acts like a(n)
Parallel Resonant
82
At very high frequencies; transmission | lines are used as
Tuned Circuits
83
This vertical angle; measured upward from the | ground
angle of elevation
84
gain of an antenna with losses ignored | have losses
Directivity
85
angle measured upward from the horizon. Used to | describe antenna patterns and directions
angle of elevation
86
combination of several antenna elements
array
87
angle between points in an antenna pattern at which | radiation is 3 dB down from its maximum
beamwidth
88
any antenna with two sections
dipole
89
an antenna used as part of an array
element
90
distance from an antenna great enough to avoid local magnetic or electrical coupling; and great enough for the antenna to resemble a point source
far-field region
91
an antenna with only one conductor; generally using ground | or a ground plane to represent a second conductor
monopole
92
the region of space close to an antenna; where the radiation pattern is disturbed by induced; as well as radiated; electric and magnetic fields
near-field region
93
representation of energy lost from an antenna by | radiation as if it were dissipated in a resistance
radiation resistance

COMMS (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions