30-05-2012, 02:04 PM
MULTIPATH PROPAGATION
[attachment=23537]
INTRODUCTION
What is an Antenna?
An antenna is a device for radiating and receiving radio waves or electromagnetic waves. The antenna is the transitional structure between free-space and a guiding device.
HOW IT WORKS?
In transmission, a radio transmitter applies an oscillating radio frequency electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves.
In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a voltage at its terminals, that is applied to a receiver.
MULTIPATH PROPAGATION
In wireless telecommunications, multipath propagation is the phenomenon that results in radio signals reaching the receiving antenna by two or more paths.
CAUSES OF MULTIPATH PROPAGATION
Causes of multipath include shadowing, ionospheric reflection and refraction, and reflection from water bodies and objects such as mountains and buildings.
EFFECTS COUNT
Multipath propagation causes jitter.
In digital radio communications such as GSM multipath propagation can cause errors and affect the quality of communications. The errors are due to intersymbol interference (ISI). Equalisers are often used to correct the ISI.
In a Global Positioning System receiver, Multipath propagation can cause a stationary receiver's output to indicate as if it were randomly jumping about or creeping. When the unit is moving the jumping or creeping is hidden, but it still degrades the displayed accuracy.
[attachment=23537]
INTRODUCTION
What is an Antenna?
An antenna is a device for radiating and receiving radio waves or electromagnetic waves. The antenna is the transitional structure between free-space and a guiding device.
HOW IT WORKS?
In transmission, a radio transmitter applies an oscillating radio frequency electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves.
In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a voltage at its terminals, that is applied to a receiver.
MULTIPATH PROPAGATION
In wireless telecommunications, multipath propagation is the phenomenon that results in radio signals reaching the receiving antenna by two or more paths.
CAUSES OF MULTIPATH PROPAGATION
Causes of multipath include shadowing, ionospheric reflection and refraction, and reflection from water bodies and objects such as mountains and buildings.
EFFECTS COUNT
Multipath propagation causes jitter.
In digital radio communications such as GSM multipath propagation can cause errors and affect the quality of communications. The errors are due to intersymbol interference (ISI). Equalisers are often used to correct the ISI.
In a Global Positioning System receiver, Multipath propagation can cause a stationary receiver's output to indicate as if it were randomly jumping about or creeping. When the unit is moving the jumping or creeping is hidden, but it still degrades the displayed accuracy.