Abstract: A new type of passive trihedral corner reflector is described which rotates the polarization of a reflected microwave beam by 90.degree. and thereby permits a reflected radar beam to be more easily distinguished by the interrogating radar system from the random reflections from nearby objects, i.e., clutter. Rotation of the incident beam is provided by locating a passive polarizing or "twist" grid of closely spaced thin parallel wires spaced above one conducting surface by air or by a dielectric to give an electric spacing from the surface of about 0.25 .lambda.. The spacing of the wires is less than 0.25 .lambda. so that the wires constitute a reflecting surface for signals polarized parallel to the wires. The reflector can have triangular or square sides which are mutually orthogonal. In a preferred embodiment the reflector is tipped forward by 35.degree. from a reference horizontal plane and tilted clockwise in a vertical reference plane by 15.degree. to optimize reflections.