26-07-2012, 10:05 AM
RADAR ENGINEERING
[attachment=28980]
Introduction
- Radar is an electromagnetic system for the detection and location of objects
(RAdio Detection And Ranging)
- radar operates by transmitting a particular type of waveform and detecting the nature of the signals
reflected back from objects
- radar can not resolve detail or colour as well as the human eye (an optical frequency passive scatterometer)
- radar can see in conditions which do not permit the eye to see such as darkness, haze, rain, smoke
- radar can also measure the distances to objects
- the elemental radar system consists of a transmitter unit, an antenna for emitting electromagnetic radiation
and receiving the echo, an energy detecting receiver and a processor.
- a portion of the transmitted signal is intercepted bya reflecting object (target) and is reradiated in all directions
- the antenna collects the returned energy in the backscatter direction and delivers it to the receiver
- the distance to the receiver is determined by measuring the time taken for the electromagnetic signal to
travel to the target and back.
The Radar Range Equation
- the radar range equation relates the range of the radar to the characteristics of the transmitter, receiver,
antenna, target and the environment.
- it is used as a tool to help in specifying radar subsystem specifications in the design phase of a program.
-If the transmitter delivers PT Watts into an isotropic antenna, then the power density(W/m 2) at a distance
R from the radar is
- here the 4πR2 represents the surface area of the sphere at distance R
- radars employ directional antennas to channel the radiated power Pt in a particular direction
- the gain G of an antenna is the measure of the increased power radiated in the direction of the target, compared
to the power that would have been radiated from an isotropic antenna
[attachment=28980]
Introduction
- Radar is an electromagnetic system for the detection and location of objects
(RAdio Detection And Ranging)
- radar operates by transmitting a particular type of waveform and detecting the nature of the signals
reflected back from objects
- radar can not resolve detail or colour as well as the human eye (an optical frequency passive scatterometer)
- radar can see in conditions which do not permit the eye to see such as darkness, haze, rain, smoke
- radar can also measure the distances to objects
- the elemental radar system consists of a transmitter unit, an antenna for emitting electromagnetic radiation
and receiving the echo, an energy detecting receiver and a processor.
- a portion of the transmitted signal is intercepted bya reflecting object (target) and is reradiated in all directions
- the antenna collects the returned energy in the backscatter direction and delivers it to the receiver
- the distance to the receiver is determined by measuring the time taken for the electromagnetic signal to
travel to the target and back.
The Radar Range Equation
- the radar range equation relates the range of the radar to the characteristics of the transmitter, receiver,
antenna, target and the environment.
- it is used as a tool to help in specifying radar subsystem specifications in the design phase of a program.
-If the transmitter delivers PT Watts into an isotropic antenna, then the power density(W/m 2) at a distance
R from the radar is
- here the 4πR2 represents the surface area of the sphere at distance R
- radars employ directional antennas to channel the radiated power Pt in a particular direction
- the gain G of an antenna is the measure of the increased power radiated in the direction of the target, compared
to the power that would have been radiated from an isotropic antenna