A square corner reflector is used in which of the following?

A reflector antenna is based upon the reflection of electromagnetic(EM) waves using a parabolic or curved surface, which reflects-focus the EM waves into a beam and directs them towards a particular point or region.

One of the Reflector types is the "Square corner reflector antenna" which is a passive device, that uses a flat reflector with three perpendicular surfaces to reflect electromagnetic waves. The three surfaces create a corner reflector reflecting the incoming waves to the source along the same path.

A square-corner reflector is a passive device used to reflect radio waves toward the emission source directly. Thus, useful for radar system calibration. Also, due to its mutually intersected perpendicular plates, it got its applications in UHF television receiving antennas, Point-to-point communication links and data links for wireless WANs Amateur radio antennas.