Radar reflectors with controllable reflection

Radar reflectors have been used to increase the reflectivity of small vessels and navigation guides for easy detection. If the reflectivity is controllable by some electrical or mechanical means, then a passive telemetry would be possible, which transfers some information from the site of a target to a radar station. This paper presents a controllable radar reflector, which consists of an array of resonant dipoles or slots combined with a reflecting plate. When the array of slots is placed at the focal plane of a Luneberg lens, an electrical or mechanical reflectivity modulation of more than 10 dB is obtained for wide angle of incidence in laboratory and field experiments. Additional features, such as sturdy structure, slight scattering, wide bandwidth (more than 4 percent at the modulation of 10 dB), easy construction and adjustment, and the optional ability of mechanical control make the slots array practical.