Fan-beam antenna

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A fan-beam antenna is a directional antenna producing a main beam having a narrow beamwidth in one dimension and a wider beamwidth in the other dimension. This pattern will be achieved by a truncated paraboloid reflector or a circular paraboloid reflector. Since the reflector is narrow in the vertical plane and wide in the horizontal, it produces a beam that is wide in the vertical plane and narrow in the horizontal. (The larger the antenna dimension, the narrower the beam.)

Circular paraboloid (red) and its truncated reflector (green)
Side and frontal view of the beam produced

AN/FPN-36 radar, with search (left) and height-finding (right)

Fan beam antennas are used in radar sets. Those in height finders have the beam oriented horizontally.