RF Behaviour

Question 1

What is Absorption?

Answer 1

If a signal does not bounce off, or move around an object, and it cannot move through the object.

example: A 2.4 GHz signal will be 1/16 the original power after propagating through a brick
wall. The same signal will only lose 1/2 the original power after passing though drywall
material

Question 2

What is Reflection?

Answer 2

A wave can bounce off a flat smooth surface that is larger than the wave. This will change the direction of the wave.

Question 3

Types of Reflection?

Answer 3

Skywave

Microwave

Question 4

What is Skywave reflection?

Answer 4

This is usually frequencies below 1GHz, such as AM radio, and a reason why you can hear a radio station that is 100’s of miles away on a clear night. The signal is bouncing off of the ionosphere.

Question 5

Microwave Reflection

Answer 5

Microwave signals exist between 1 GHz and 300 GHz. These can bounce off of much smaller objects like a metal door.

Question 6

Scattering?

Answer 6

When a signal is passing through a medium of smaller particles then scattering could become an issue to the strength of the signal.

Question 7

Refraction?

Answer 7

When a signal passes through a different type of medium (such as liquid) this medium could cause the signal to be “bent”

Question 8

Diffraction?

Answer 8

A signal is bent, but in this case around an object, not passing through a different medium

Question 9

Multipath ?

Answer 9

Propagation phenomenon that results in two or more paths of a signal arriving at a receiving antenna at the same time or within nanoseconds of each other. This can often be caused by reflection.

Question 10

Causes of Multipath ?

Answer 10

Cancelling or weakening other signals (nulling / down fade)
Increasing the amplitude (up fade)
Causing corruption (data corruption)

Question 11

Attenuation?

Answer 11

This is the loss of signal strength over distance. At some point the amount of
energy is too low for the receiving antenna to detect. This could also be known as free-space-
path-loss

Question 12

Gain ?

Answer 12

Known as amplification or increased amplitude. A signal’s amplitude can be boosted by the use of external devices.

Question 13

Types of Gain ?

Answer 13

Active Gain

Passive Gain

Question 14

Active Gain ?

Answer 14

is usually caused by the transceiver or the use of an amplifier on the wire that connects the transceiver to the antenna.

Question 15

Passive Gain ?

Answer 15

Focusing the RF signal with the use of an antenna