25-06-2012, 03:27 PM
Radio Frequency (RF) and Radio Technology Fundamentals
[attachment=25448]
The Concept of Line-of-Sight (LOS)
No obstructions between each end
No trees
No buildings
No mountains
Can you go through a window?
Probably, but with added losses that are hard to predict:
Plan on 10dB as an initial guess, can be greater for reflective (metallic) tinted glass
The Line-of-Sight Issue – using a repeater
A system approach called a “repeater” can establish line-of-sight to go around or over obstacles
Active repeaters (two radio systems back-to-back)
Passive repeaters (one radio system redirected)
Modulation
Method of sending information over radio wave
By changing the signal phase over time one can send information
Example QPSK (Quadrature Phase Shift Keying):
4 decisions points
2 code bits per symbol
RF is Attenuated by Rainfall
Signals above 11 GHz can be severely affected
Most of Proxim’s products operate below 6 GHz and are virtually unaffected by rainfall in most parts of the world
RF Reflection and Multipath
RF can “bounce” off objects like buildings and mountains, water and atmosphere
Different paths of RF will arrive at destination at different times - this is called ‘multipath’
[attachment=25448]
The Concept of Line-of-Sight (LOS)
No obstructions between each end
No trees
No buildings
No mountains
Can you go through a window?
Probably, but with added losses that are hard to predict:
Plan on 10dB as an initial guess, can be greater for reflective (metallic) tinted glass
The Line-of-Sight Issue – using a repeater
A system approach called a “repeater” can establish line-of-sight to go around or over obstacles
Active repeaters (two radio systems back-to-back)
Passive repeaters (one radio system redirected)
Modulation
Method of sending information over radio wave
By changing the signal phase over time one can send information
Example QPSK (Quadrature Phase Shift Keying):
4 decisions points
2 code bits per symbol
RF is Attenuated by Rainfall
Signals above 11 GHz can be severely affected
Most of Proxim’s products operate below 6 GHz and are virtually unaffected by rainfall in most parts of the world
RF Reflection and Multipath
RF can “bounce” off objects like buildings and mountains, water and atmosphere
Different paths of RF will arrive at destination at different times - this is called ‘multipath’