The corner reflector is a passive device used to directly reflect radio waves back toward the emission source. Therefore, the corner reflector is a useful device for radar system calibration. In general, the corner reflector consists of mutually intersected perpendicular plates. The commonly seen corner reflectors are dihedral and trihedral.

While the dihedral corner reflector is sensitive to its mechanical alignment, the trihedral corner reflect is highly tolerant to misalignment. This offers a convenient way for quick field setup. The trihedral corner reflector is made with three right angle plates which is illustrated in the figure below.

The effective area is calculated by
Where “a” is the side length of the trihedral.

The effective radar cross section is calculated by

Where λ is the wavelength of the radar signal.

In trihedral corner reflectors, the waves that hit the corner reflector are bounced by each surface, three times total to result in reversed direction waves sending back towards the source. Therefore, the trihedral corner reflectors provide a very high Radar Cross Section (RCS) target for radar system testing and characterizations.

The calculated radar cross section and relative magnitude of a 10” edge length (7.07” side length) trihedral reflector is shown in the plots below. From the chart you can see that the radar cross section is frequency dependent. For a given sized reflector, the lower the frequency, the smaller the RCS.

RCS seen from an angle follows a cosine relationship. That is, when there is an angle of incident wave, the RCS should be multiplied with a factor of (cos(theta))^2.

E.g., at boresight, theta is 0, factor is 1; when theta is 45 deg, factor is 0.5.