The orientation and construction of high efficiency passive radar targets

Abstract

A study of the conventional meteorological radar target, aluminized paper over an inverted tetrahedral wood frame, shows that it has very poor performance at low angles of elevation in precisely the region where it is likely to move out of radar range in clear weather. An octahedral target, constructed from the same materials, but having a different orientation, has a much improved performance over this conventional target at low elevations. The dihedral reflection is the most important factor in this improved performance, but the better use of the standard trihedral reflection at these low elevations is also important. The downgrading of the reflections from a trihedral corner assembled in the field, usually taken to be 10 dB below that from a perfect trihedral, is overpessimistic; and at low angles of elevation, with the improved orientation of the target, a value of 5 dB is more realistic for maximum radar range calculations. Various uses of dihedral reflectors are discussed. It is pointed out that a square flat plate rotating about a diagonal would be a highly efficient tester of anechoic chambers.