Lecture 3

Question 1

What is an antenna?

Answer 1

An antenna is a device that converts electromagnetic waves (radiated energy) into guided waves or vice versa.

Question 2

What is the guided wave in an antenna?

Answer 2

The guided wave is typically transmitted through a coaxial cable attached to the antenna.

Question 3

What is the radiated energy in an antenna?

Answer 3

The radiated energy is characterized by the antenna’s radiation pattern, which describes how the antenna radiates energy into space.

Question 4

What is azimuth?

Answer 4

The term azimuth refers to the horizon or the horizontal plane.

Question 5

What is elevation?

Answer 5

the term elevation refers to the vertical plane

Question 6

What is an isotropic radiator?

Answer 6

An isotropic radiator is a hypothetical antenna that radiates energy equally in all directions.

Question 7

What is gain?

Answer 7

Gain refers to the ratio of the power gain in a specific direction to the power gain of a reference antenna in the same direction. The reference antenna is typically an isotropic radiator.

Question 8

What is polarization?

Answer 8

Polarization refers to the orientation of the electromagnetic wave as it travels through space. Antennas are sensitive to specific types of electromagnetic waves and are often linearly polarized

Question 9

What are the two main categories of antennas based on directionality?

Answer 9

Omnidirectional antennas have 360 degree coverage.
Directional antennas have limited range of coverage.

Question 10

How is gain measured in antennas?

Answer 10

Gain is measured in dBi (decibels relative to an isotropic radiator) and dBd (decibels relative to a dipole antenna)

Question 11

What is link budget?

Answer 11

Link budget is a way of quantifying the performance of a communication link.

Question 12

What factors determine the received power in an 802.11 link?

Answer 12

The received power in an 802.11 link is determined by the transmit power, transmitting antenna gain, and receiving antenna gain.

Question 13

What is the minimum received signal level in a wireless communication link?

Answer 13

The minimum received signal level of the receiving radio must be less than the received power, minus the free space loss of the link path, in order for a link to be possible.

Question 14

What is the link margin in a wireless communication link?

Answer 14

The difference between the minimum received signal level and the actual received power is called the link margin. A positive link margin (ideally at least 10 dB or more) is necessary for a reliable link.

Question 15

What is free space loss?

Answer 15

The power of an electromagnetic signal is diminished by the geometric spreading of the wavefront, also known as free space loss.

Question 16

How does free space loss affect the power of an electromagnetic signal?

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Answer 16

The power of the signal is spread over a wavefront, the area of which increases as the distance from the transmitter increases.

Question 17

What is the equation for calculating free space loss at a frequency of 2.4 GHz in decibels?

Answer 17

The equation for calculating free space loss at a frequency of 2.4 GHz in decibels is: Lfs = 100 + 20*log10(d), where d is the distance in kilometers.

Question 18

What is the equation for calculating free space loss at any frequency in decibels?

Answer 18

The equation for calculating free space loss at any frequency in decibels is: Lfs = 32.45 + 20log(d) + 20log(f), where d

Question 19

What is MIMO?

Answer 19

MIMO stands for Multiple Input, Multiple Output and refers to the use of multiple antennas at both the transmitter and receiver to improve the performance of a wireless communication system.

Question 20

What are the benefits of MIMO systems?

Answer 20

MIMO systems can increase the capacity, coverage, and reliability of wireless networks.

Question 21

How do MIMO systems increase capacity?

Answer 21

MIMO systems use spatial multiplexing, which allows multiple data streams to be transmitted over the same frequency band simultaneously.

Question 22

How do MIMO systems improve coverage and reliability?

Answer 22

MIMO systems use beamforming, which directs the transmit signal towards the receiver to improve the signal-to-noise ratio (SNR).

MIMO systems can also improve the performance of a wireless network by using spatial diversity, which involves transmitting the same data over multiple antennas to improve the reliability of the transmission.