The History of Radar | Radar History: Isle of Wight Radar During The Second World War | Radar: The Basic Principle
Radar Technology: Main Components | Radar Technology: Side Lobe Suppression | Radar Technology: Airborne Collision Avoidance
Radar Technology: Antennas | Radar Technology: Antenna Beam Shapes | Radar Technology: Monopulse Antennas | Radar Technology: Phased Array Antennas | Radar Technology: Continuous Wave Radar | Theoretical Basics: The Radar Equation
Theoretical Basics: Ambiguous Measurements | Theoretical Basics: Signals and Range Resolution
Theoretical Basics: Ambiguity And The Influence of PRFs | Theoretical Basics: Signal Processing | Civilian Radars: Police Radar | Civilian Radars: Automotive Radar | Civilian Radars: Primary and Secondary Radar
Civilian Radars: Synthetic Aperture Radar (SAR) | Military Applications: Overview | Military Radars: Over The Horizon (OTH) Radar
How a Bat's Sensor Works | Low Probability of Intercept (LPI) Radar | Electronic Combat: Overview | Electronic Combat in Wildlife
Radar Countermeasures: Range Gate Pull-Off | Radar Countermeasures: Inverse Gain Jamming | Advanced Electronic Countermeasures

A means of detecting hostile activities from far away, at day or night, through rain and snow, operating at the speed of light and with pinpoint accurracy - this is what radar is for the military. Most probably, military applications outnumber all other radar applications in science, meteorology and air traffic control. A few of these applications are listed below.

Radars work as sensors to put a given area under surveillance, find targets therein, track their movements, and direct other weapons or countermeasures against them. Other applications like navigation and weather radar are also used by the military. Identification Friend or Foe (IFF) is covered in the entry about Primary and Secondary Radar.

Surveillance

Applications

Ground Penetrating Radar. Landmines, buried some centimetres below the surface, are very dangerous weapons not only in wartime but also for decades afterwards. The landscapes of countries like Angola, Cambodia, the former Yugoslavia and even the deserts of Libya are still contaminated with leftovers from wars that are long finished. Ground-penetrating radar can be used to find and subsequently destroy these mines because radar signals are not completely absorbed or reflected at the boundary between air and ground, but can penetrate into soil, provided that the moisture content is not too high.

Area Surveillance or Ground Surveillance. Most of these radars are small devices (about the size of a business suitcase) mounted on tripods. They serve as a kind of sentry to keep an 'eye' on an area and issue an alert as soon as something is going on. This function is also performed by JSTARS, an airborne MTI (moving target indicator) radar that puts a whole battlefield under surveillance and monitors movements like march columns on the ground. A prototype was successfully used during Desert Storm in 1991.

Air Surveillance. Monitoring the airspace is essential for detecting hostile aircraft and directing defensive measures against them. The first such application was the British Chain Home of World War II. In general, radars cannot look around corners - therefore, these radars are usually located on elevated places in order to achieve maximum coverage area. Better coverage, especially against ground-hugging aircraft, can be obtained if the radar is mounted on an airborne platform such as AWACS (Airborne Warning and Control System). Some radars can look around corners: Over The Horizon (OTH) radars exploit certain features of Earth's atmosphere and can detect low-flying objects out to distances of thousands of kilometres.

Target Tracking

Tracking radars intend to keep a pair of virtual crosshairs centred on a target. They are built around Conical Scan or Monopulse antennae which yield very precise angle measurements. The readings are taken as input to direct gunfire or to control missile weapons.

The ultimate systems in terms of hardware and software complexity are tracking radars built with monopulse phased array antennae. This is accomplished by either splitting an antenna array into four sub-arrays or illuminating the array with a monopulse feed. By switching the antenna's beam position and beam shape, such radars are capable of tracking multiple targets at the same time, doing target searches in between, and transmitting guidance commands to missiles, or illuminating a target so that a missile-seeker head can find it.

Applications

Shell-tracking. Radar can detect all kinds of airborne objects, and artillery shells are among them. Shell-tracking radars are used for improving the accuracy of an aircraft's own fire and for measuring the flight trajectory of hostile projectiles, in order to calculate their point of origin.

Ballistic Missile Early Warning (BMEWS) and Ballistic Missile Defence. This is where the big ones are. The requirement for high angular resolution at long ranges leads to really huge antennae. The antennae for ABM (anti ballistic missile) phased array radars such as Cobra Dane or Pave Paws can easily take on the dimensions of multi-storey buildings.

The latest project in this area is the GBR (Ground Based Radar), which is a part of the American NMD (Nuclear Missile Defence) incentive. Also called X-band Radar because of the frequency band employed, it is used to find and track incoming long range missiles or individual warheads, preferably before they reach the summit of their trajectory.

Finally...

Many radars aren't simply built to perform one or the other of the above functions but to integrate them in a single device. A fighter-borne air intercept radar needs to perform surveillance in order to find its target, and it needs to switch into a tracking and target illumination mode of operation once engagement has begun. The same is true for shipborne equipment like AN/SPY-1 or AEGIS. Limited available space on the platform dictates that several functions be performed by the same hardware and, in particular, through the same antenna. If these functions have been combined professionally, the radar must be called a system rather than a device - otherwise the radar is nothing more than a weak compromise.

Because radar is such a formidable force multiplier, denying an opponent the benefits of using their radars is a discipline of its own. More about that can be found in the entries around the entry Electronic Combat.

History: Overview | Isle of Wight Radar During WWII
Technology: Basic Principle | Main Components | Signal Processing | Antennae | Side Lobe Suppression | Phased Array Antennae | Antenna Beam Shapes | Monopulse Antennae | Continuous Wave Radar
Theoretical Basics: The Radar Equation | Ambiguous Measurements | Signals and Range Resolution | Ambiguity and PRFs
Civilian Applications: Police Radar | Automotive Radar | Primary and Secondary Radar | Airborne Collision Avoidance | Synthetic Aperture Radar
Military Applications: Overview | Over The Horizon | Low Probability of Intercept | How a Bat's Sensor Works
Electronic Combat: Overview | Electronic Combat in Wildlife | Range Gate Pull-Off | Inverse Gain Jamming | Advanced ECM | How Stealth Works | Stealth Aircraft