Cwna Chapter 2 Radio Frequency Fundamentals

Front 1

Wireless communitcations travel across what is known as a ________ _________ which does not contain the signal and is free to radiate into the surrounding environment in all directions.

Back 1

Unbounded Medium

Front 2

The range of all possible electromagnetic radiation.

Back 2

Electromagneic Specturm (EM)

Front 3

An RF signal starts out as _______ ________ which is generated by a transmitter.

Back 3

alternating current (AC)

Front 4

The fluctuation of voltage in an AC currents is known as

Back 4

oscillation (cycling)

Front 5

RF signals that travel through a vacuum can move at the speed of

Back 5

light or 300,000,000 meters per second

Front 6

The distance between two successive crests (peaks) or two successive trough (valleys) of a wave pattern is known as

Back 6

wavelength

Front 7

The length of a 2.45 GHz wave is about how long?

Back 7

4.8 inches

Front 8

The length of a 5.775 GHz wave is about how long?

Back 8

2 inches

Front 9

The number of times a specified event occurs within a specified time interval is known as

Back 9

Frequency

Front 10

An event that occurs once in 1 second can be measured in what? The standard measurement of frequency.

Back 10

Hz (Hertz)

An event that occurs 325 times in one second is measured as 325 Hz.

Front 11

1 hertz (Hz) =

Back 11

1 cycle per second

Front 12

1 kilohertz (KHz) =

Back 12

1,000 cycles per second

Front 13

1 megahertz (MHz) =

Back 13

1,000,000 (million) cycles per second

Front 14

1 gigahertz (GHz) =

Back 14

1,000,000,000 (billion) cycles per second

Front 15

2.4 GHz WLAN RF signals oscillates at?

Back 15

2.4 billion times per second

Front 16

The height of a wave is measured in what? Also known for an RF signals strength or power.

The higher the wave the stronger the

Back 16

Amplitude

Front 17

The amount of amplitude that leaves a radio transmitter is known as

Back 17

Transmit amplitude

Front 18

When a radio receives an RF signal, the received signal strength is most often referred to as what?

Back 18

Received amplitude

Front 19

Two or more signals that share the same frequency.

Back 19

Phase

Front 20

Phase is measured in....

Back 20

distance, time, and degrees

Front 21

The peaks of two signals with the same frequency are in exact alignment is know as what? When the peaks are not in exact aligment they are known as what?

Back 21

in phase; out of phase

Front 22

The way in which RF waves move is known as?

Back 22

Propagation

Front 23

The most common RF behavior in which a signal does not bounce off an object, move around an object, or pass throgh an object.

Back 23

absoption

Most materials will absorb some amount of an RF signal to varing degrees. Water is the main culprit for absorbing RF signals.

Front 24

RF behavior in which the wave hits a smooth objects that is larger than the wave itself and may bounce in another direction.

Back 24

Reflection

In legacy 802.11 standards a,b, and g reflections is a major source of poor WLAN performance

Front 25

Multiple relections of an RF signal is known as what? These occur when the electromagnetic signals wavelength is larger than pieces of whatever medium the signal is relecting from or passing through.

Back 25

Scattering

Front 26

The bending of and RF signal is known as what? Occurs when an RF signal passes through a medium with a different density.

Back 26

refraction

Front 27

The bending of an RF signal as it encounters an object.

Back 27

diffraction

Front 28

The decrease of amplitude or signal strengh is known as what?

Back 28

Loss (Attenuation)

Front 29

The loss of a signal strength caused by the natural broadening of the waves.

Back 29

Free space path loss (FSPL) or Beam Divergence

Front 30

A propagation phenomenon that results in two or more paths of a signal arriving at a receiving antenna at the same time.

Back 30

Multipath

When a signal encounters an object, it may reflect, scatter, refract, or diffract. These propagation behaviors can all result in multiple paths of the same location.

Front 31

The use of external devices to boost a signals strengh is known as?

Back 31

Gain (Amplification)

Front 32

An amplifier is usually ____________ meaning it increases the AC voltage both inbound and outbound.

Back 32

bidirectional

Front 33

The ways a WLAN engineer can deal with destructive multipath issues are:

Back 33

Use of directional antennas

Antenna diversity

Reducing transmit power or using lower gain antennas

Front 34

The three most common causes of refraction are what?

Back 34

Water vapor, changes in air temperature, and changes in air pressure

Front 35

The materials concreate, wood, and asphalt that "soak up" an RF signal can all cause what?

Back 35

absorption

Front 36

The movement of a radio wave from transmitter to receiver is commonly called?

Wave ascension

Wave transmission

Wave propagation

Wave migration

Back 36

Wave transmission

Front 37

The following behaviors of waves as the propagate are:

Back 37

Absorption

Reflection

Scattering

Refraction

Deffraction

Loss (Attenuation)

Multipath

Front 38

When multiple RF signal paths arrive at the receiver at the same time and are 180 degrees out of phase with the primary wave. The result is known as what?

Back 38

Nulling

Front 39

________ _________ is accomplished by focusing the RF signal with the use of an antenna. Focuses the signal more powerfully in one direction than another.

Back 39

Passive Gain

Front 40

The characteristics that exist in every RF signal are:

Back 40

Wavelength

Frequency

Amplitude

Phase

Front 41

If an 802.11 RF transmission reaches a receiving antenna simultaneiously by direct and reflected paths, what effect will the reflected signal have on the signal that took the direct line-of-sight path?

Back 41

The signals maybe distorted if the indirect signal arrives simultaneiously at the receiver and is > than 90 degreees, but less than 180 degrees.

Front 42

The time difference between the signals in multipath propation is known as what?

Back 42

delay spread