Fan-beam antenna

In a parabolic antenna, the feed horn is placed at the focal point and irradiate the reflector.

The latter send back in space a highly focused parallel beam that one can describe as pencil shape.

Primary radar in airport have often fan-beam with the section of antenna oriented horizontally to give a narrow beam in azimuth.

They must then be complemented with a height finders have the beam oriented horizontally because they cannot locate the altitude.

Those have their reflector rotated 90 degrees and produce a beam that is wide in the horizontal plane but narrow in the vertical.

Side and frontal view of the beam produced
Circular paraboloid (red) and its truncated reflector (green).
AN/FPN-36 radar, with search (left) and height-finding (right)