Clutter (Radar)

Under Clutter refers to goals that captures the radar and displays, but they are undesirable because they reduce the probability of detection of the actual objectives (the term is taken from the English language and called clutter and mess ). The application of this concept is inconsistent from radar to radar. When an airplane is flying in a dense cloud, then the echo signals this cloud for the air surveillance radar are a Wetterclutter. However, this cloud is for the weather radar exactly very important, the echo signal of the aircraft disturbs the other hand, and is thus referred to as the weather radar clutter.

Ground clutter

The electromagnetic waves from a radar device are reflected on all electrically conductive surfaces, including to homes, terrain and even on wet foliage of trees. These echo signals are undesirable in some radars and are therefore called ground clutter. An elderly German -language name is called fixed target echoes. This permanent echoes form on the monitor large-scale cloudy, the rings are centered around their own location, as on the ground disappear because of the curvature of the earth distant objects behind the horizon. This collection of fixed target echoes in the center of the screen used to be called " Local Rose". Within this local rose a recognition of an airplane with a small target character was almost impossible because the fixed target echoes have brightened this area completely.

Since these fixed targets always have a constant distance to the also fixed location of the radar unit, the echoes from fixed targets in amplitude and phase are relatively constant and can be filtered out by special modules ( moving target indication MTI).

With an increasing number of wind power plants, the radar surveillance is difficult. The wings of the wind power plants consist partly of carbon fibers and therefore reflect well. They also have a Doppler frequency by the rotation and therefore can not be suppressed by the MTI. In the picture above the ground clutter without Doppler frequency is up to a distance of 20 nautical miles already filtered out ( the very bright ring is the brand for 25 nautical miles).

Seaclutter

As Sea clutter echoes are referred derived from sea waves. Through the wind get this sea- clutter a small Doppler frequency and are therefore very difficult to suppress. In practice, an STC function is usually used to suppress the disturbances occurring mostly at close range.

Wetterclutter

From Wetterclutter is when clouds, rain, snow or fog can be recorded and displayed by a surveillance radar as targets. Since here the wind causes the relative motion radar, these false echoes are sometimes also by the moving target indication.

However, this noise usually originate from a so-called target volume (as opposed to point target ), and therefore this fault can be mitigated by the use of the circular polarization.

Chaff

As a military application, additional reflecting surfaces are ejected into the atmosphere, which will interfere with a surveillance radar. These light -reflecting objects ( thin strips of aluminum foil or metallized glass fibers) hold by the thermals relatively long in the air, form extended bright areas on the screen and chaff are called.

To achieve a large effective reflection area, the lengths of these strips or fibers to be tuned to the wavelength of the radar.

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