Method and apparatus for verifying the authenticity of a radio frequency responsive target

摘要

A method and apparatus for authenticating an object which produces an analog radio frequency signature in response to an interrogating signal. The object is illuminated with toe interrogating signal, and the analog ratio frequency signature is received from the object in response to the interrogating signal. The analog radio frequency signature is digitized to produce a digitized response signal, and the digitized response signal is normalized to produce a normalized digitized response signal. The normalized digitized response signal is then converted to a code word. The code word is compared to a plurality of valid code words. The object is determined to be authentic only if the code word matches one of the plurality of valid code words. <??>A method for forming a radio frequency responsive target formed of a pattern of thin dipoles which produce a composite analog radio frequency signal in response to an interrogating signal. A first metallic film layer is deposited on top of a non-conductive substrate. The pattern of thin dipoles is generated such that each of the thin dipoles has a position and an angular orientation within the pattern of thin dipoles. An etchant resistant pattern is deposited on top of the first metallic film layer, the etchant resistant pattern corresponds to a photographic image of the pattern of thin dipoles. A second metallic layer is applied on top of the first metallic film layer. The second metallic layer occupies areas on the first metallic film layer where the etchant resistant pattern is absent and the second metallic layer has a thickness equal to the thickness of the etchant resistant pattern. The etchant resistant pattern is removed in order to expose portions of the first metallic film layer. The second metallic layer and the portions of the first metallic film layer are etched simultaneously until the portions of the first metallic film layer have been removed from the non-conductive substrate. <IMAGE>