Directional Antenna Array (Multi-View)

A single dipole antenna radiates energy in all directions perpendicular to its axis. In a plot like the one above on the left (xy plane), this would look like energy radiating out equally to the left and right of the antenna (with the antenna shown as a short vertical black line segment in the xy plane, lined up along the y axis). But if we put two antennas in proximity, spaced a quarter wavelength apart and with a 90-degree electrical phase shift, there is a clear directionality. This array of antennas radiates preferentially rightward, with very little going leftward. Whatever energy is emitted leftward seems to immediately wrap around and become a part of the rightward waves. The plot on the right is the view from above (in the xz plane, looking down parallel to the antenna axes).