Cosecant squared antenna

A cosecant squared antenna, sometimes known as a constant height pattern, is a modified form of parabolic reflector used in some radar systems.

[1] It is shaped to send more radio energy in certain directions in order to smooth out the reception pattern of objects as their range changes in relation to the radar.

The terrain return at further distances is much a weaker signal due to the radar equation.

The slant range distance between the radar and the terrain is the cosecant of the angle between the fuselage and the target, and the energy falls off with the fourth root of that number.

The opposite modification could also be used, bending the upper lip outward, with the same basic outcome.