Fraunhofer-Gesellschaft
Discovery of radar
The foundations for the development of radar were laid by Heinrich Hertz: in 1886, while gathering experimental data to demonstrate the existence of electromagnetic waves, he discovered that radio waves are reflected by metallic objects. Within the framework of his experiments he used special reflectors. In 1904, the German high frequency technician Christian Hülsmeyer carried out the first detection experiments using radar waves. While experimenting with Hertz's reflector, he noticed that electric waves that were emitted from a transmitter and reflected by a metal surface can be used to detect distant metallic objects. He then developed a device that could measure the transit time of reflected waves: the telemobiloscope. On 30 April 1904, he took out a patent for the process and is therefore the inventor of radar.
Another important discovery during the development of radar was the verification of the Doppler effect. With this effect, radar can be used to determine whether or not a detected object is moving. It is named after the Austrian physicist and mathematician Christian Doppler, who predicted the effect in 1842.
Current applications
Radar and high frequency techniques find application in many areas of daily life. The most common examples are surely the radar systems on ships as well as in air traffic for monitoring and navigation. It can, however, also be used for a wide range of scientific purposes, e.g. in the fields of geodesy, archaeology and meteorology (weather radar). Further applications include the measurement of the near-Earth orbit to gain new insights but also to protect space travel through enhanced space situational awareness. Other areas that use radar techniques include the automotive industry (e.g. driver assistance systems), the manufacturing industry (e.g. imaging radar for quality management) as well as the environment and energy sector (e.g. needs-based activation of warning lights on wind turbines). In addition to these production-oriented application areas, radar is used to protect civil and military installations. It is also widely used in the reconnaissance and detection of hidden dangerous objects or unstable structures (slopes after heavy storms or in mining areas, damaged buildings, snow slabs in the mountains etc.).