Radar systems, like cars, come in a variety of sizes and have different performance specifications. Some radar systems are used for air-traffic control at airports and others are used for long-range surveillance and early-warning systems. A radar system is the heart of a missile guidance system. Small portable radar systems that can be maintained and operated by one person are available as well as systems that occupy several large rooms.
Radar systems are usually classified according to specific function and installation vehicle. Some common examples are listed below:
Function installation vehicle search - ground or land based Track - Airborne
Height-finder - Shipboard
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 modem warfare. As a result, modern warships, aircraft, and shore stations usually have several radar systems, each performing a different function.
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.
The preceding paragraphs indicated that radar systems are divided into types based on the designed use. This section presents the general characteristics of several commonly used radar systems. Typical characteristics are discussed rather than the specific characteristics of any particular radar system.
Search radar, as previously mentioned, continuously scans a volume of space and provides initial detection of all targets within that space. Search radar systems are further divided into specific types, according to the type of object they are designed to detect For example, surface-search, air-search, and height-finding radars are all types I of search radar.