Editing Corner reflector (section)

==In radar==
{{multiple image
| align = center
| direction = horizontal
| header   = Corner reflectors used in radar
| image1   = Radarreflektor auf einer Motoryacht 3596.JPG
| caption1 = Octahedral corner reflector on the mast of a yacht. 
| width1   = 150
| image2   = buoy seal.jpg
| caption2 = Buoy in San Diego Harbor. Metal plates near the top form corner reflectors to reflect radar signals
| width2   = 148
| image3 = Radar reflector at Alte Brücke (Frankfurt am Main).jpg
| caption3 = Radar reflector on an [[abutment]] of a bridge
| width3 = 300 
| image4   = NTS - Reflector Tower.jpg
| caption4 = A multireflector at the [[Nevada Test Site]] used as radar target for simulated nuclear bombing
| width4   = 176
| footer   = <!-- Ack! {{notelist}} doesn't seem to work here, so approximate -->Note: The diamond-shaped corner reflector on the yacht is improperly deployed; to best reflect surface radar it should be deployed in the so-called "rain-catching" configuration so as to present an inside corner as shown on the "radar testing" image. 
}}

Radar corner reflectors are designed to reflect the [[microwave]] [[radio waves]] emitted by [[radar]] sets back toward the radar antenna.  This causes them to show a strong "return" on radar screens.  A simple corner reflector consists of three conducting sheet metal or screen surfaces at 90° angles to each other, attached to one another at the edges, forming a "corner".  These reflect radio waves coming from in front of them back parallel to the incoming beam.  To create a corner reflector that will reflect radar waves coming from any direction, 8 corner reflectors are placed back-to-back in an [[octahedron]] (diamond) shape.  The reflecting surfaces must be larger than several [[wavelength]]s of the radio waves to function.<ref>{{cite book|last1=Kraus |first1=John |last2=Marhefka |first2=Ronald |title=Antennas for All Applications |edition=3rd |date=2002|publisher=McGraw Hill|isbn=0-07-112240-0|page=365}}</ref>

In maritime navigation they are placed on [[bridge]] abutments, [[buoy]]s, [[ship]]s and, especially, [[Lifeboat (shipboard)|lifeboats]], to ensure that these show up strongly on ship radar screens.  Corner reflectors are placed on the vessel's masts at a height of at least {{convert|4.6|m|ft|abbr=in}} above sea level (giving them an approximate minimum [[horizon]] distance of {{convert|8|km|nmi|round=0.5|lk=out|abbr=off|sp=us|disp=or}}).  [[Marine radar]] uses [[X-band]] microwaves with wavelengths of {{convert|2.5|-|3.75|cm|in|round=0.5|abbr=in}}, so small reflectors less than {{convert|30|cm|in|abbr=in}} across are used.  In aircraft navigation, corner reflectors are installed on rural [[runway]]s, to make them show up on aircraft radar.

An object that has multiple reflections from smooth surfaces produces a radar return of greater magnitude than might be expected from the physical size of the object. This effect was put to use on the [[ADM-20 Quail]], a small decoy missile which had the same [[radar cross section]] as a [[B-52]].

The corner reflector is not the only efficient radar reflector design; other [[retroreflector]] designs have also seen use. [[Luneburg lens]], for example, are used on the [[ADM-141 TALD]].<ref>{{cite web |title=IMI ADM-141 TALD |url=https://www.designation-systems.net/dusrm/m-141.html |website=www.designation-systems.net}}</ref>