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.
Figure 2: A truncated paraboloid reflector
This type of antenna system is generally used in height-finding equipment (if the reflector is rotated 90 degrees). Since the reflector is narrow in the horizontal plane and wide in the vertical, it produces a beam that is wide in the horizontal plane and narrow in the vertical. In shape, the beam of a height-finding radar is a horizontal fan beam pattern.
Figure 3: Heightfinder PRV-17 “Odd Group”
Figure 1: Fan-beam antennae pattern
a) lateral view
b) frontal view