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Radar Beam

rotating
fan beam
pencil beams

Figure 1: Different main lobes of the antenna pattern of a ship's radar, partly pencil beams, but also fan beams

rotating
fan beam
pencil beams

Figure 1: Different main lobes of the antenna pattern of a ship's radar, partly pencil beams, but also fan beams

rotating
fan beam
pencil beams

Figure 1: Different main lobes of the antenna pattern of a ship's radar, partly pencil beams, but also fan beams

Radar Beam

A directional radar antenna concentrates the transmitting energy in a narrow sector. This sector is described by the points at which the transmitted power was reduced by the half. The area within these half-power points is defined as the radar beam, and it contains nearly 80 percent of all the transmitted energy. It is usually a cone-shaped cutout from a sphere, mostly sharply focused (pencil beam), but sometimes much wider in one dimension (fan beam).

With a continuous wave radar this geometric form is completely filled with the transmitted power. With very short transmission pulses, this section is not completely filled with the transmission energy, but only a small volume, the so called resolution cell. A radar beam is then the path that guides the travel of the transmitted impulse.