Parabolic Dish Reflector

A parabola has the geometric property that every ray arriving parallel to its axis reflects to a single focus (and vice versa). Placing a small feed—often a horn—at that focus turns its spreading wavefront into a flat, collimated wavefront leaving the dish, concentrating energy into a narrow, high-gain beam. Gain rises with the square of the dish diameter in wavelengths, so large dishes at microwave frequencies achieve enormous gain and pinpoint directivity.

Satellite TV and ground stations, microwave backhaul links, and radio astronomy.