Definition

Radar clutter. The visual indication on a situation display of unwanted signals.

Source: ICAO Doc 4444 PANS-ATM

Description

The electromagnetic signals processed by the radar receiver (especially for PSR) consist of three main components:

• useful signal (echoes from aircraft)
• clutter, which comprises:
  • echoes from targets other than aircraft (e.g. birds, clouds, terrain, buildings, etc.)
  • signals received by lobes other than the main one (e.g. side lobes).
  • multiple reflections, e.g. instead of radar-aircraft-radar, the path of the signal can be radar-aircraft-terrain-radar
• noise, which can be:
  • external, e.g. random ambient electromagnetic signals on the frequency, used by the radar.
  • internal (i.e. caused by processes in the receiver itself). It exists in all electronic equipment.

If the combined signal (useful+noise+clutter) is shown on the situation display directly, two problems occur: