Serviceline Industrial Sensors
Serviceline Explosion Protection

Glossary of Radar Sensors

Use our glossary to get an overview of some key terms from the field of radar technology and radar sensor technology and their definitions.

Term Description
Absorption Partial or even complete absorption of the electromagnetic energy of a radar signal by a medium. Absorption effects in the form of attenuation caused by rain or fog, for example, are primarily relevant for long-range radar systems that operate in the very high frequency range. If a radar sensor from Pepperl+Fuchs is to be used in industrial applications to "see through" a medium to detect the actual measurement target, any absorption effects caused by the intermediate medium must be taken into account. However, these do not normally lead to any significant functional impairment of the sensor.
Antenna radiation pattern Graphical representations of the directional characteristics of a (radar) antenna, usually visualized as a horizontal, vertical, or computer-aided 3-D antenna pattern. A horizontal antenna pattern is recommended for easily recording the directivity of a radar antenna, as it quickly shows the relationship between the main, rear, and side beams.
Corner reflector Corner reflectors or radar reflectors are an effective means of significantly increasing the effective reflective surface of an object with low or unstable reflectivity. Corner reflectors designed in the form of a triple mirror consist of three electrically conductive surfaces positioned at a 90° angle to each other. The electromagnetic waves arriving in the corner reflector are reflected back in their original direction due to the multiple reflections created here.
CW radar Short for "continuous wave radar" or unmodulated continuous wave radar. Contrary to pulse radar, the emitter continues to operate continuously during the measurement process and emits electromagnetic waves with a constant frequency and amplitude. However, distance measurement is not possible due to the lack of a time reference for the emitted signal.
Doppler effect A phenomenon named after the Austrian physicist Christian Doppler. It describes the temporal compression or stretching of a signal that occurs when the distance between the emitter and receiver changes during the duration of the signal. Based on this change in propagation time, radar sensors are able to measure radial velocities and detect whether an object is moving towards or away from the sensor.
Electromagnetic wave The term electromagnetic wave or Hertzian wave covers the various types of wavelength ranges within the electromagnetic spectrum. This includes radio waves and microwaves, infrared radiation, visible light, UV light, X-rays, and gamma rays. Radar sensors from Pepperl+Fuchs operate in the frequency range of 122.25 ... 123 GHz and therefore use so-called radar microwaves. As electromagnetic waves do not need a carrier medium to propagate, radar sensors are particularly reliable and are therefore less dependent on influences (such as wind, pressure, temperature) that could affect such a medium.

FMCW radar

Short for "frequency-modulated continuous wave radar". In contrast to pulse radar and CW radar, the emitting element continues to operate continuously during the measurement process and also runs a frequency ramp, usually in the form of sawtooth modulation or triangular modulation. The resulting frequency shift, in conjunction with other variables, allows the distance to the detected object to be calculated.
I&Q method The so-called I&Q method or "In-Phase & Quadrature method" enables a radar sensor to detect whether an object is moving towards or away from the sensor. For this purpose, a second signal shifted by 90°(quadrature) is emitted in addition to the actual signal (in-phase). The direction of movement of the detected object can be detected by evaluating which of the two signals is leading and which is lagging at the receiver.
ISM band The ISM bands (industrial, scientific, and medical band) are frequency ranges that can be used by radio frequency devices in industry, science, medicine, and domestic and similar fields without a license and usually without a permit. Industrial radar sensors also generally operate in the ISM band and are therefore easy to use in a wide range of applications.
Patch antenna Antenna type frequently used in radar sensors. Patch antennas are characterized by their compact design and the fact that they can be applied directly to a circuit board. They are also particularly suitable for use in the microwave range, where the wavelengths are so short that the patches can be kept correspondingly small. To increase the antenna gain and directivity, several patches are connected via strip lines and combined as an array.
Magnetic permeability or magnetic conductivity refers to the permeability of a material to magnetic fields. It results from the ratio of the magnetic flux density to the magnetic field strength. Compared to the permittivity, the relative permeability of an object does not usually have a major influence on the reflected radar signal.
Permittivity The permittivity describes the permeability of a material to electric fields. It is specified as the product of the permittivity of the vacuum and the substance-dependent permittivity number of the respective material. If a radar sensor is to "see through" certain materials in order to detect the actual target, for example, the lowest possible relative permittivity or low transmission loss is advantageous.
Pulse radar Contrary to continuous wave radars, which continuously emit electromagnetic waves, pulse radars emit individual, short but powerful pulses. Pulse radars are suitable for long detection ranges and have a correspondingly high power consumption. This type of radar is primarily used in the military section, in air traffic control, or as precipitation radar. This sensing principle is less suitable for applications in industrial automation, such as on Auto-Guided Transport Systems or mobile machines, as the electronic components required to generate the powerful pulses would take up too much space and the resolution is relatively low.
Radar Radar is short for "radio detection and ranging" and refers to a range of methods and devices for detection and localization based on electromagnetic waves in the radio frequency range. Basically, a radar device emits a bundled electromagnetic wave as a primary signal. Echoes reflected from objects in the radar's detection range are received and evaluated as a secondary signal.
Radar cross-section (RCS) The radar cross-section, or RCS (short for radar cross-section), is an object-specific quantity that describes the extent to which a radio wave is reflected back through an object in the direction of the emitter. The shape of the object, the nature of the material, the wavelength, and the angle of incidence and reflection of the radiation all have an effect here. The radar cross-section of an object is given in square meters.
Radar equation The radar equation, or basic radar equation, is a physical calculation method that relates the energy emitted by a radar device or radar sensor to the energy reflected back. The radar equation can be used to predict the maximum range at which a target object can be detected by the respective radar, provided that certain relevant variables are known. The radar equation therefore offers an effective method for assessing the performance of radar devices or radar sensors.
Radar reflection The electromagnetic waves reflected by an obstacle in the detection range of the radar device or radar sensor. This reflection forms the basis for all measured variables or findings that can be obtained using radar technology (e.g. distance, speed, direction of movement, reflection amplitude, object contours).
Radome Radome is an artificial word for "radar dome", a dome construction to protect a radar antenna from external influences. Depending on the size of the antenna structure they protect, radomes can be impressive in size: The world's largest radome (TIRA space observation radar), for example, reaches a diameter of 47.5 meters. The basic requirement for radomes is that they should reflect, absorb, refract, or scatter the electromagnetic radiation emitted or received by the antenna structure as little as possible and cause the lowest possible transmission loss. This is particularly relevant as the nature of the radome as a so-called "two-way attenuation" affects the electromagnetic radiation on both the emitter and receiver paths.
Reflection In an application, which is solved by radar sensors, it is speculated that an emitted wave is diffusely scattered by an object in such a way that at least a certain part of the wave is reflected back to the point of emission. The strength of this reflection (amplitude strength) depends very much on the nature and material of the object.
Speed of light The electromagnetic waves used as a signal by radar devices propagate in a vacuum at approximately 300,000 km/s, the speed of light. If the electromagnetic waves propagate in a material (e.g., air), this material reduces the propagation speed accordingly, depending on its permittivity and permeability. Nevertheless, it remains in a range that is far superior to sound (343.2 m/s in dry air at 20 °C).
Voltage controlled oscillator (VCO) A voltage controlled oscillator (VCO for short) is a central component of a radar device or radar sensor. It generates the high-frequency vibration required for the radar signal. Its output frequency is proportional to the input voltage.


Subscribe to our newsletter and receive regular news and interesting information around the world of automation.

amplify–The Pepperl+Fuchs Magazine

Discover our online magazine! Exciting success stories, application reports, interviews, and regional news are awaiting you.

Radar sensors from Pepperl+Fuchs

Pepperl+Fuchs industrial radar sensors offer you interference-free distance and velocity measurement—even in rain, fog, wind, or dust. Learn more about this unique sensory operating principle and all the advantages it opens up for you.