Effective Aperture of Antenna Directivity Bounding and its Radiation Aperture

In this paper, among the earliest type of antennas in production was aperture type. These antennas were rigid and consisted of a parabolic, paraboloidal, cylindrical, or spherical shape. A major limitation of this type of antenna stems from the fact they could only give one particular radiation pattern, and if one wanted to scan the signal from one point to another, then the whole structure had to be moved which meant the satellite had to be realigned. This major shortcoming led to the development of the more costly phased array technology and other technologies where beam scanning was exploited. The aperture is defined as the area, oriented perpendicular to the direction of an incoming radio wave, which would intercept the same amount of power from that wave as is produced by the antenna receiving it. At any point, a beam of radio waves has an irradiance or power flux density which is the amount of radio power passing through a unit area of