Oct 7
What is Radar, Its History and How Does It Work?
- Furkan Sağlam
- Oct 8
- 9 min read
The history of radar technology, spanning from the past to the present, has been shaped by the collaborative efforts of scientists and has reached its current level of advancement through numerous innovations developed in various fields. Radars play vital roles in military defense systems, civil aviation, and meteorology, becoming the cornerstone of safe transportation, effective weather control, and accurate weather forecasts. Thanks to technological advancements, radars continue to become increasingly sensitive, faster, and more functional, becoming an indispensable part of modern life.
Now let's quickly answer your questions such as what is radar and how does it work, which waves are used in radars, and when was radar invented.
Contents
What is Radar?
Radar is a technology used to detect objects at long distances. It derives from the first letters of the phrase "Radio Detection and Ranging." It is commonly used in aircraft and marine vehicles, meteorology, airports, and traffic control.
How Does Radar Work?
A radar device sends electromagnetic radio waves toward a target, which are reflected by objects like metal-surfaced aircraft, missiles, or rain. The returned signal provides information such as the object's distance, direction, speed, shape, and range. The radar receiver collects the reflected signal and determines the object's distance by measuring the wave's travel time. By tracking the target's position over time, its future trajectory can be predicted.
Radar data is processed digitally. This allows us to identify the detected object and make decisions accordingly.
Various types of radar are used in aviation, serving different purposes:
Area, Surveillance and Approach Radars allow air traffic controllers to track and direct aircraft regionally.
Precision Approach Radars (PARs) provide precision guidance support to landing aircraft, particularly in low visibility conditions.
Ground Movement Radars monitor aircraft and vehicle movements within the airport area.
Weather radars inform pilots about dangerous weather events such as storms.
Radio Altimeters precisely measure the aircraft's height above the ground.
Secondary Surveillance Radars enable additional information from the aircraft, such as identity and flight level, to be transmitted to the controller.
Which Waves Are Used in Radars?
Radar operates using radio waves and microwaves, based on the principle that the waves it emits hit an obstacle and are reflected back. The most commonly used radar wavelength frequencies are:
S-band (2–4 GHz) : Air traffic control and meteorology
X-band (8–12 GHz) : Military radars, police speed radars
L-band (1–2 GHz) : Long-range air defense systems
Ka-band (27–40 GHz) : Satellite and precision radars
Radar Types
Radars are divided into two main groups: those that detect and those that do not.
Imaging radars process signals from the target to produce map-like images. These types of radars are typically used in weather observation and military air surveillance. Non-imaging radars, on the other hand, present their measurements as numerical values. These systems are often used in radar altimeters (altitude measurement), speed meters, or some automobile keyless ignition systems (immobilizers).
On the other hand, there are different radars with various technical features today.
What are Primary Radars?
Primary radar systems transmit high-frequency signals and detect the echoes created when these signals hit a target and bounce back. In other words, the target's presence, location, and movement are determined by evaluating the reflections of the transmitted signals themselves. These types of radars do not require any active hardware on the target.
Secondary Radars
In secondary radar systems, the aircraft must be equipped with a transponder (transponder). This transponder receives and encodes specific signals sent from the radar system and provides a response. These responses include not only distance but also additional data such as altitude, identification information, and technical malfunctions (e.g., radio malfunction). Therefore, secondary radars provide more detailed information than primary radar systems.
Pulsed Radars
These radars send out very short but powerful signals, then wait for echoes to come in. By taking into account the antenna orientation and the signal's round-trip time, the target's direction, distance, and altitude can be determined.
Continuous Wave Radars
In continuous wave radars, signal transmission continues uninterrupted. Both transmission and reception occur simultaneously. The transmitter and receiver can be located far apart. A powerful broadcast source (such as a TV station) can even act as a transmitter, while a receiver in another location can analyze the incoming signals and determine the target's location. Systems operating on this principle are also called passive radars.
Unmodulated Continuous Wave Radar (Unmodulated CW Radar)
This type of radar transmits signals at a fixed frequency and a constant amplitude. Its most common use is for speed measurement. The Doppler effect is used to determine the target's speed. However, distance cannot be measured. It is most commonly seen in radar speed guns used by police.
Frequency Modulated Continuous Wave Radar (FMCW Radar)
In these systems, the frequency of the transmitted signal is varied over time. This allows for measuring not only speed but also distance or altitude. Because it provides a continuous data stream, measurement results are obtained instantly. Furthermore, because it allows for uninterrupted measurement, it is particularly preferred in applications requiring precise, real-time tracking.
Intrapulse Modulated Radars
These systems send pulses at lower power but with longer duration. The pulse duration is modulated by parameters such as frequency and phase. This allows for more precise distance measurements by compressing the pulse. These systems combine the advantages of both pulse and continuous wave radars.
Bistatic Radar Systems
Bistatic radars are radar systems where the transmitter and receiver are positioned far apart. This placement provides several tactical advantages. By collecting signals reflected from the target from different angles, more information can be obtained. This is particularly important in defensive and surveillance applications.
Doppler Radar
It has a single antenna that both transmits and receives reflected signals. Radar pulses are very short, emitted approximately 1,300 times per second. The radar spends most of its time listening to the returned signals. The antenna rotates at various elevation angles and scans to observe weather phenomena at different levels. This allows meteorologists to monitor the structure and evolution of storms at different altitudes.
What is Aesa Radar?
AESA (Active Electronically Scanned Array) active phased array radars contain thousands of small electronically steered transceiver modules. They can rapidly change the direction of signals without the need for mechanical movement. These radars offer advantages such as greater range, higher resolution, the ability to track multiple targets simultaneously, and high resistance to electronic jamming. They are widely used in modern fighter aircraft, air defense systems, and naval platforms.
What is Mobile Radar?
Mobile radar systems are easily transportable and can be quickly deployed to different locations. They are typically mounted on trucks, trailers, or specialized vehicles. They are preferred when fixed radar infrastructure is not feasible or when rapid response is required in volatile threat environments. They are common in military applications but are also used in areas such as traffic control and border security.
What is Mobile Radar?
Mobile radar is a radar system that can be used on the move without being tied to a fixed location and is generally used for traffic enforcement. It is used by law enforcement agencies to conduct speed checks on vehicles with civilian or official license plates. It can be carried on or in vehicles and can be deployed temporarily at different locations. It is more flexible and less predictable for drivers than fixed radar systems.
How to Understand Mobile Radar?
Mobile radars are typically hidden in vehicles with civilian license plates. The radar device is usually located behind the windshield, in the rear seat area, or in the trunk. A small camera or radar antenna may be located in the front or rear window of the vehicle. These vehicles are often parked on the side of the road, appearing empty. Locals also call them "radar cars."
What is KGYS Radar?
KGYS (City Security Management System) radars are fixed radar systems used for urban security purposes, such as speed enforcement and license plate recognition. They are typically located fixedly at traffic lights, intersections, and main streets. They automatically detect speed violations and transmit license plate information to the relevant authorities through the system. They are used both to ensure traffic safety and to combat crime throughout the city.
What is Weather Radar?
Weather radars are radar systems used to detect, track, and monitor objects in the atmosphere (aircraft, helicopters, unmanned aerial vehicles, etc.). They are used in both civilian and military settings. Various types are found in air traffic control towers, fighter jets, air defense systems, and meteorological observations. They are critical for both flight safety and anticipating threats.
When Was Radar Invented?
The first practical radar system was produced in 1935 by British physicist Sir Robert Watson-Watt , and by 1939 Britain had established a series of radar stations along its south and east coasts to detect attackers by air or sea.
Historical Development of Radars
The development of radar technology is not the work of a single person or country. Radar has evolved over time with the contributions of numerous scientists from various nations, and its current form has been the result of numerous independent discoveries and innovations. Here are some important milestones in radar history:
1865 – James Clerk Maxwell (Scotland): He proposed the theory of the electromagnetic field, proving that electric and magnetic fields propagate as waves at the speed of light. This formed the basic physical basis of radar.
1886 – Heinrich Hertz (Germany): Proved the existence of electromagnetic waves by experimentally confirming Maxwell's theory.
1897 – Guglielmo Marconi (Italy): He was the first to transmit electromagnetic waves over long distances. These studies laid the foundation for wireless communication.
1900 – Nikola Tesla: Proposed that moving metal objects could be detected by using the reflection of electromagnetic waves.
1904 – Christian Hülsmeyer (Germany): Developed the first practical radar system, called the " telemobiloskop ", to monitor ship traffic in bad weather conditions and applied for a patent.
1921 – Albert Wallace Hull (USA): Developed the magnetron , an efficient radar transmitter tube.
1922 – Albert H. Taylor & Leo C. Young (USA): First detected a wooden ship using electromagnetic waves.
1930 – Lawrence A. Hyland (USA): First detected an aircraft using electromagnetic waves.
1931 – William AS Butement & PE Pollard (England): First put forward the idea of radar with a system proposal, but it did not receive government support.
1933 – Rudolph Kühnhold (Germany): Drawing on his experience with sonar, he designed a radar-like device (Funkmessgerät). These studies laid the foundation for the Freya Radar.
1935 – Robert Watson-Watt (England): Proposed that aircraft could be detected remotely using radio waves. In 1939, a defense network was established with secret RDF (Radio Direction Finding) stations placed off the coast of England.
1936 – George F. Metcalf & William C. Hahn (USA): They developed the klystron tube used in radar systems.
1939 – Randall & Boot (England): They developed a powerful yet compact radar with a multicavity magnetron. It was integrated into B-17 bombers and used to detect German submarines at night and in fog.
1940 – Erich Hüttmann (Germany): Filed a patent on the principle of intrapulse modulation and pulse compression.
1940 – Radar systems were now being developed in the United States, Germany, Russia, Japan, and France. During World War II, radar made a major leap forward in the military sphere.
1950 – The SLAR (Side-Looking Airborne Radar) principle was developed.
1951 – Carl A. Wiley (USA): Discovered the principle of Doppler-Beam Sharpening (DBS), a method of increasing resolution using Doppler frequency.
1952 – The first working Synthetic Aperture Radar (SAR) was developed.
1953 – The first SAR flight test was conducted on the 930 MHz frequency.
1956 – Telefunken introduced the first mass-produced speed detection radar (VRG-1) for police use.
1960 – SLAR images began to be used in civilian areas.
1972 – The first SAR imaging of the moon was performed during the Apollo 17 mission.
1978 – Seasat , launched on June 27, became the first civilian satellite with SAR technology.
Information About Radar Systems
Which animal was the radar inspired by?
Radar technology was inspired by bats . Bats use biological sonar to navigate and hunt in dark environments: the ultrasonic sound waves they emit hit objects and bounce back, gathering information about their surroundings from these echoes. Scientists have developed radar systems that operate using electromagnetic waves, taking this principle as an example. Therefore, radar emerged directly from bats' ability to echolocate (orient using echolocation).
What is Fighter Jet Radar Lock?
Radar lock means that after a fighter aircraft's radar systems detect a target, they continue to track it constantly and transmit a continuous signal. This "lock-on" state allows the pilot to monitor the target's speed, position, and heading in real-time. Radar lock is generally necessary for missile guidance systems to function; once the lock is achieved, missiles can be precisely guided to the target. Enemy pilots usually detect a radar lock through their warning systems.
What is a Radar Magnetron?
A magnetron is a vacuum tube used to generate high-frequency microwaves in radar systems. It generates electromagnetic waves by directing electrons with a magnetic field. These microwaves are sent through the radar antenna, and the reflected signals are analyzed. Magnetrons played a critical role in early radar systems, particularly those developed during World War II. They are similarly used in modern microwave ovens, but magnetrons in radar applications are more sensitive and powerful.
What is the Use of Surface Radar?
Surface radars are used to detect and track ships, boats, divers, or other surface objects. They play a particularly important role in maritime and defense. These radars can detect targets even beyond visual range by reflecting electromagnetic waves from the sea surface. They are used in a variety of tasks, including preventing collisions between ships, target acquisition, ensuring port security, and tracking surface threats.
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