How radar works: the technology made famous by war


Radar was one of the most important technical breakthroughs of WWII. The technology helped Britain and its allies emerge victorious from the Battle of Britain, the air war fought over British skies in 1940, according to Imperial War Museums (IWM).

Radar – which stands for Radio Detection and Ranging – is a detection system that uses radio waves to locate objects. It is still widely used today, but as technology has advanced they now often exploit microwaves, according to the Earth observation laboratory. These are found at the higher frequency end of the radio spectrum and provide more accurate readings.

Related: What is electromagnetic radiation?

Invention of the radar

While this literal fire test made radar a household name, the technology behind it emerged much earlier and centered on the study of electromagnetic (EM) waves.

EM radiation is a form of energy that is everywhere and can take many different forms, such as radio waves, microwave, X-rays, gamma rays and ultraviolet (sunlight). Electromagnetic waves are also the basis for the operation of mobile phones and wireless computer networks.

And in 1885 he was a Scottish physicist James clerk maxwell who came up with the idea that perhaps radio waves could be reflected from metallic objects, just like light waves.

air traffic control radar

Human air traffic control operators need to keep a constant eye on their radar screens. (Image credit: Getty)

A few years later, the German physicist Heinrich Hertz set out to prove it. In an experiment he conducted in 1888, he discovered that they were indeed reflective. As the first person to apply Maxwell’s theories, the unit of frequency of an electromagnetic wave was named hertz after him, Live Science Previously reported. In 1904, a patent was issued to a German engineer named Christian Hülsmeyer for what was called “an obstacle detector and a ship’s navigation device”. Not a catchy name, but nonetheless – an early type of radar system was born.

Despite this, it was not until the 1930s that the technology was needed, mainly due to the invention of long-range military bombers, which prompted countries to invest in a system capable of detecting their approach and to provide early warning, depending on Encyclopedia Britannica.

All the major world powers of the time continued their research, but it was the United States and the United Kingdom that were able to refine the technology. Scottish physicist Sir Robert Watson-Watt, known as “the father of radar”, took the science that preceded it and created the functional system that formed the basis of modern radar, according to the Royal society.

How does the radar work?

A typical system has four main components, namely:

• Transmitter: The source of the radio pulse.

• Antenna: Needed to send the pulse into the ether and receive it when it is reflected.

• Switch: This tells the antenna when to transmit or receive pulses.

• Receiver: Required to detect and transform the pulses, which return in a visual format to be read by an operator.

The process of directing artificial radio waves at objects is called illumination. Although radio waves are invisible to the human eye as are optical cameras. According to Nasa, they are sent at about 300,000,000 meters per second – the speed of light.

Some of the reflected radio waves (echoes) are sent back to the radar where they are received and amplified, with the data interpreted by skilled operators using computers, according to the Australian Bureau of Meteorology. When returned, they provide information such as distance and bearing.

Radio waves are inexpensive to generate, can pass through snow, haze and fog, and are harmless, unlike gamma and X rays.

Radar can be used to detect ships, planes, and satellites, or closer to home – radar guns are used by police to calculate how fast cars are going, ones that are going too fast in line for one. speeding, according to Encyclopedia Britannica. Meteorologists also use radar to map and track weather systems around the world.

Battle of britain

Germany lost more than 1,700 planes in the Battle of Britain, almost twice as many as the British. (Image credit: Getty)

During the Battle of Britain, radar enabled the RAF to detect incoming German planes using radio waves, according to the RAF Museum website.

From radar towers scattered throughout the south and east of the country, the system would send out these waves, which would continue to travel until they collided with something, such as an incoming aircraft, and were bounced back for pickup by the receiver. By calculating how long it took for the waves to return, skilled operators could determine the altitude, range and bearing of incoming enemy aircraft, according to the RAF.

In doing so, he gave the RAF enough time to scramble their own planes to deal with the incoming threat. Being in the right place at the right time helped the UK win the battle and deal a fatal blow to Third Reich invasion plans, according to a radar operator’s account published by the BBC.

Doppler radar

doppler radar

Police fast guns use Doppler radars to track the speed at which vehicles are moving. (Image credit: Getty)

Without a doubt, one of the greatest advances in post-war radar technology has been Doppler radar, according to the Encyclopaedia Britannica. With the need to defend against bombers now gone, the new motivation for refining the technology was to use it to track the weather.

While ordinary radar can determine distance and location, Doppler can also give us information about the speed of an object. It works on the principle of Doppler effect, the idea that the waves produced by an object will constrict if it goes towards you, or will spread out if it moves away.

This is used to track weather systems that are constantly in motion, depending on the National Oceanic and Atmospheric Administration (NOAA).

They can also collect a huge amount of information, so modern Doppler radars depend on increasing processing power. Doppler Radar is also what you’ll find in a police pistol!

Resources and further reading

You can observe and follow live the precipitation detected by NOAA radar technology using the Radar Viewer Interactive Web Page.

Interested in learning more about how radar technology is transforming transportation safety? Hear from a panel of experts at the Future of the Car Summit 2020 in this video by NXP.


“Robert Alexander Watson-Watt. April 13, 1892 – December 5, 1973”. Biographical Memories of Members of the Royal Society (1975).

“Great challenges in the processing of the radar signal”. Radar signal processing (2021).

“Clear Atmosphere Doppler Radar Survey”. Bulletin of the American Meteorological Society (1978).


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