Beam shaping by moving the phase center of array antenna

The phase pattern of an antenna can be expressed with reference to an arbitrary point in space such that the phase over the range of directions of interest becomes constant. This point is called the phase center of the array, from where the antenna radiation appears to emanate. In general, an antenna does not have a unique phase center for all the directions of observation. This is due to the fact that theoretically a point emanates a spherical wavefront and the radiated wavefront from the array antenna, which has some finite dimensions, will not be therefore purely spherical with fixed curvature in all the direction of observations. The location of the phase center is a function of observation angle. An array antenna can be focused at some finite distance by moving the phase center of antenna and a flat-top beam can be obtained. This paper describes the effects of moving the phase center of an array antenna to change the shape of the beam by changing its beamwidth. It also discusses the movement of phase center in a planar array.