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Wireless Midterm (Chapters 1-5) > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

Few Statements that will help to interpret the radiation charts?

A

Azimuth chart - H-plane = Top-down view

Elevation chart = E-plane = side view

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2
Q

What are azimuth chart and elevation chart referred to?

A

Polar charts

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3
Q

What is a beamwidth?

A

Beamwidth is the measurement of how broad or narrow the focus of an antenna is, and is measured both horizontally and vertically.

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4
Q

What are some Antenna Types?

A

Omnidirectional
Semidirectional
Highly Directional

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5
Q

What is Omnidirectonal antenna?

A

Omnidirectional Antenna radiates RF in fashion similar to the way a table or floor lamp radiates light. All directions

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6
Q

What is Semidirectional Antenna?

A

They radiate RF in a fashion similar to the way a wall sconce radiates light away from the wall or the way a street lamp shines down a street or a parking lot.
Providing a directional light across a large area

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7
Q

What is a highly directional antenna?

A

Radiate RF in a fashion similar to the way spotlight focuses light on a flag or a sign.

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8
Q

When are Omnidirectional Antennas used?

A

They are used in point-to-multipoint environments.

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9
Q

Where are Semidirectional Antennas commonly used?

A

To provide a network bridge between two building in a campus environment or down the street from each other.

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10
Q

Three types of semidirectional antennas?

A

Patch
Panel
Yagi

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11
Q

What is patch antenna?

A

Particular way of designing the radiating elements inside the antenna.
Used for outdoor point-to-point communications.

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12
Q

When are highly directional antennas used?

A

Strictly used for point-to-point communications. To provide network bridging between two buildings. Most narrow beamwidth.

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13
Q

Two types of highly directional antennas?

A

Parabolic Dish Antenna

Grid Antenna

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14
Q

What is an Antenna Array?

A

Is a group of two or more antennas that are integrated together to provide coverage. These antennas operate together to perform what is known as beamforming.

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15
Q

What is a beamforming?

A

Beamforming is a method of concentrating RF energy. Concentrating a signal means that the power of the signal will be greater and the SNR at the receiver should therefore also be greater, providing better transmission.

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16
Q

Three different types of beamforming?

A

Static Beamforming
Transmit Beamforming
Dynamic Beamforming

17
Q

What is a Static Beamforming?

A

Performed by using directional antennas to provide a fixed radiation pattern.
Uses multiple directional antennas, all clustered together.

18
Q

What is a Dynamic Beamforming?

A

Focuses the RF energy in a specific direction and in a particular shape. The radiation pattern of the signal can change on a frame by frame basis.

19
Q

What is Transmit Beamforming?

A

Is performed by transmitting multiple phase-shifting signals with the hope and intention that they will arrive in phase at the location where transmitter believes that the receiver is located. Pattern is not dynamic

20
Q

What is a Fresnel Zone?

A

Path of the visual LOS between two point-to-point antennas.

21
Q

What is a MIMO?

A

Multiple Input Multiple Output

Take advantage of multipath. Wireless radio architecture that can receive or transmit using multiple antennas concurrently.

22
Q

What is the definition of the horizontal beamwidth of an antenna?

A

The distance between the two -3dB power points on the horizontal axis, measured in degrees.

23
Q

The fresnel zone should not be blocked by more than what percentage to maintain a reliable communications link?

A

40 Percent

24
Q

The size of Fresnel zone is controlled by what factors?

A

Distance

Frequency

25
Q

When a long-distance point-to-point link is installed, earth bulge should be considered beyond what distance?

A

7 Miles

26
Q

Which of the following are true for antenna diversity?

A

The transreceiver samples both antennas and chooses the best received signal from one antenna.

Transreceivers can transmit from only one of the antennas at a time

27
Q

The ratio between the maximum peak voltage and minimum voltage on a line is known as what?

A

VSWR

28
Q

What are some of the possible negative effects of an impendence mismatch?

A

Erratic Signal Strength
Decreased signal amplitude
Amplifier/transmitter failure

29
Q

When determining the mounting height of a long-distance point-to-point antenna, which of the following needs tobe considered?

A

Frequency
Distance
Earth Bulge
RF line of sight

30
Q

Which of the following are true about cables?

A

They cause impedance on the signal

They add loss to the signal

31
Q

Lightning arrestors will defend against what?

A

Transient currents

32
Q

The radius of the second Frensel zone is?

A

Out of phase with the point source

Larger than the first frensel zone

Wireless Midterm (Chapters 1-5) (5 decks)

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