Figure 1-23.Joint service classification system.
No single radar system has yet been designed that can perform all of the many radar functions
required by the military. Some of the newer systems combine several functions that formerly required
individual radar systems, but no single system can fulfill all the requirements of modern warfare. As a
result, modern warships, aircraft, and shore stations usually have several radar systems, each performing a
One radar system, called SEARCH RADAR, is designed to continuously scan a volume of space to
provide initial detection of all targets. Search radar is almost always used to detect and determine the
position of new targets for later use by TRACK RADAR. Track radar provides continuous range, bearing,
and elevation data on one or more targets. Most of the radar systems used by the military are in one of
these two categories, though the individual radar systems vary in design and capability.
Some radar systems are designed for specific functions that do not precisely fit into either of the
above categories. The radar speed gun is an example of radar designed specifically to measure the speed
of a target. The military uses much more complex radar systems that are adapted to detect only fast-
moving targets such as aircraft. Since aircraft usually move much faster than weather or surface targets,
velocity-sensitive radar can eliminate unwanted clutter from the radar indicator. Radar systems that detect
and process only moving targets are called MOVING-TARGET INDICATORS (mti) and are usually
combined with conventional search radar.
Another form of radar widely used in military and civilian aircraft is the RADAR ALTIMETER. Just
as some surface-based radars can determine the height of a target, airborne radar can determine the
distance from an aircraft to the ground. Many aircraft use radar to determine height above the ground.
Radar altimeters usually use frequency-modulated signals of the type discussed earlier in the chapter.