Radar is a device that emits electromagnetic waves to detect the position and speed of an object and analyzes the reflected waves for information. The Doppler effect is used to determine the speed of an object, and the detected information is used to identify the object. It plays an important role in various fields such as military, meteorology, and aviation.
We’re in Country X’s operations center, deep underground in a bunker. In the center of the room, a large, square screen is lit up, with blinking green dots. It’s friendly fire. As everyone stands tensely in front of the screen, a red dot suddenly appears on the screen and moves quickly. “General, an enemy ballistic missile is incoming!”, ‘Intercept immediately!’, the urgent voice of someone in the crowd, the general’s orders. Soon the red dot disappears and the people are relieved. The large screen in the center of the bunker is a radar screen. It has long been a key piece of equipment in military strategy and defense, and its development has changed the face of warfare and is considered essential on the modern battlefield.
As such, radar is a device that detects which objects are moving in which direction and at what speed, and displays that information to the user. The process by which radar detects objects is similar to how the eye sees things. The eye can see an object by detecting the light reflected from it. Radar also detects objects by sending out electromagnetic waves and analyzing the reflected waves. Nevertheless, the exact workings of radar can be a bit confusing because it’s a concept that we don’t often encounter in our daily lives. To make it easier to understand, let’s take a look at how radar works in a little more detail. The process of radar detecting an object can be broken down into three steps: emitting electromagnetic waves, measuring and analyzing the reflected waves, and identifying the object.
First, radar emits electromagnetic waves in all directions. Electromagnetic waves are waves created by rapidly changing electric or magnetic fields, and include all the waves we know as visible light, infrared light, ultraviolet light, and X-rays. All waves have two characteristics: frequency and wavelength, which are inversely related: the higher the frequency, the smaller the wavelength. This creates a conundrum for radar users: the shorter the wavelength, the higher the resolution of the radar, but the higher the frequency, the easier it is for the waves to be absorbed or reflected by the air, making it harder to detect farther away. The key is to select and emit electromagnetic waves of the right wavelength, depending on the purpose of the radar. For example, a radar to detect ships emits electromagnetic waves with a relatively longer wavelength than a weather radar to detect water droplets in the air.
However, in addition to the choice of electromagnetic waves, the environment in which the radar is installed is also very important. In mountainous areas or urban centers with many skyscrapers, radar signals can bounce off many objects, making accurate detection difficult. Radar is also highly affected by the weather. In poor weather conditions, radar signals can be distorted or absorbed by climatic phenomena. To address these issues, modern radar systems employ more complex algorithms and filtering techniques to filter out unnecessary information and improve accuracy.
When emitted electromagnetic waves hit an object, the object reflects them back. The reflected electromagnetic waves are called reflected waves. The reflected waves also spread in all directions from the object, and the radar measures and analyzes the waves that are reflected back in the direction of the radar. By analyzing the waves, the radar can learn a lot of information about the object, most notably the distance from the object, the size of the object, and the speed of the object. By measuring the time it takes for the emitted wave to reflect and return, the distance can be easily calculated using the formula distance=time×speed (electromagnetic waves are a type of light, so the speed of electromagnetic waves is the speed of light). Also, by analyzing the direction from which the reflected waves returning from the object are coming, the shape of the object can be roughly determined, and the size of the object can be calculated. But how do we find the speed of an object? To find the speed of an object, we need a special theory of physics. This theory is actually related to a phenomenon that we often encounter in our daily lives.
We’re standing at a train station, and a train comes rushing by, making a miraculous sound. The sound is relatively high as the train approaches from a distance, and relatively low as it moves away from the station. This is due to the Doppler effect. The Doppler effect is that when an observer looks at the waves emitted by an object, the waves are higher than the original frequency when they are moving closer together, and lower frequency waves when they are moving away from each other. The same applies to radar and reflected waves. By measuring how much the frequency of a reflected wave has increased or decreased, you can get important information about an object’s speed and direction. In the early days of radar, radar could only tell you the position of an object, but by utilizing the Doppler effect, it could tell you the speed of an object. Because of this, the Doppler effect is a big part of how radar works.
In terms of military applications, radar played a big role in detecting fighters and bombers during World War II. Since then, radar technology has evolved rapidly, and today it’s used not only in the military, but also in civil aviation, ocean exploration, weather prediction, and many other fields. In missile defense systems in particular, accurate radar detection can be the difference between winning and losing a war. For example, radar’s role in pinpointing and intercepting the trajectory of missiles fired by enemy forces is essential. As a result, fast and accurate information gathering via radar is essential on the modern battlefield, and the technology is constantly improving.
But radar’s job doesn’t end there. It needs to identify objects based on the information it has analyzed. Radar usually has a wide detection range of 10 to 100 kilometers, and within this range, there are many objects that send reflected waves to the radar, such as water droplets, birds, clouds, etc. Therefore, it is essential to filter out unnecessary information and identify the objects we want to detect with radar. At this stage, the size, reflectivity, and speed of the object are the main criteria used. The selection criteria depends on the purpose of the radar. For example, if the radar is used to detect ships in the sea, the size should be set to 100 or more and the reflectivity should be in the reflectivity range corresponding to the material of the ship’s surface (metal, cement) to easily filter out unnecessary information such as fish or floating objects. If the radar is intended to detect missiles, a minimum threshold speed of 1 Mach (340 m/s) and a range of appropriate size and reflectivity would be sufficient to identify them. Modern military radars can even identify which fighter jets are of which nationality and which type, so the story of the X-command center is not fiction.
To summarize how radar detects an object, here’s how it works The radar sends out electromagnetic waves of the right wavelength for the target and its purpose, and when the waves bounce back from the object, the radar analyzes the information in the reflected waves to determine the distance to the object, the size of the object, and its speed. Next, the radar identifies and selectively displays the objects it wants to detect. This is how radar works, and it’s used as a human “second pair of eyes” in many fields. Useful in weather observation, air traffic control systems, undersea exploration, missile defense, marine search, and more, radar is another treasure of modern science.
