Chapter
11
Radar Principles
Introduction |
|
|
|
|
|
|
183 |
Types of Pulsed Radars . . . . . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. |
. |
183 |
Radar Applications . . . . . . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. |
. |
184 |
Radar Frequencies |
|
|
|
|
|
|
185 |
Pulse Technique |
|
|
|
|
|
|
185 |
Distance Measurement - Echo Principle . . . . . . . . . . |
. . |
. . |
. . |
. . |
. |
. |
186 |
Theoretical Maximum Range |
|
|
|
|
|
|
187 |
Primary Radars . . . . . . . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. . |
|
.188 |
The Range of Primary Radar . . . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. |
. |
189 |
Radar Measurements |
|
|
|
|
|
|
191 |
Radar Resolution . . . . . . . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. |
. |
191 |
Moving Target Indication (MTI) . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. . |
|
.191 |
Radar Antennae |
|
|
|
|
|
|
192 |
Questions . . . . . . . . . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. . |
|
.194 |
Answers . . . . . . . . . . . . . . . . . . . . . |
. . |
. . |
. . |
. . |
. |
. |
196 |
181
11 Radar Principles
Principles Radar 11
182
Radar Principles 11
Introduction
Radar stands for RAdio Detection And Ranging and was developed prior to World War II. It was used both on the ground as well as in the air by the military. Originally it used pulses for its operation but subsequently continuous wave (CW) techniques were also developed for other functions such as the radio altimeter, because CW radars have no minimum range limitation. Today radar is also extremely important in civil aviation. It is used by ground based radars in the control, separation and navigation of aircraft as well as in airborne systems for weather warning and navigation.
Radar Principles 11
Radar is the Transmission of Electromagnetic Radio Energy and the Detection of some of the 
back at the point of Transmission
Figure 11.1
Types of Pulsed Radars
A Primary Radar uses pulses of radio energy reflected from a target i.e. it uses one frequency throughout.
A Secondary Radar transmits pulses on one frequency, but receives on a different frequency i.e. the object transmits its own energy. It is a system utilizing an interrogator and transponder; the transponder can be located in the aircraft or on the ground.
This will be covered in detail in Chapter 14.
183
11 Radar Principles
Principles Radar 11
Radar Applications
Radar has a wide range of applications as follows:
Air Traffic Control uses radar to:
•monitor aircraft in relation to each other whilst they are flying on airways, in control zones or in the airfield vicinity, and to vector the aircraft if necessary.
•provide radar talk-down to a given runway (Surveillance Radar Approach (SRA) or a military Precision Approach Radar (PAR)).
•control and monitor aircraft on ILS let-downs, or during airfield instrument approaches.
•provide information regarding weather e.g. storm clouds.
Air/Ground navigational systems use radar:
•Secondary Surveillance Radar provides ATC with information regarding an aircraft’s call sign, altitude, speed, track history, destination and type of emergency when appropriate.
•Distance Measuring Equipment (DME) provides a pilot with very accurate slant ranges from a ground based receiver/transmitter known as a transponder.
Airborne Weather Radar (AWR) is used to:
•depict the range and bearing of clouds.
•indicate areas of the heaviest precipitation and associated turbulence.
•calculate the height of cloud.
•ground map.
184