| 摘要 |
An identification tag (300) is provided comprising a multilayer assembly incorporating, in sequence, a metal backing layer (320), a bulk structural layer (330), a piezo-electric layer (340) and an electrode layer (350). The electrode layer (350) incorporates antennae structures for receiving interrogating radiation comprising a first radiation component at a relative ly lower frequency and a second radiation component at a relatively higher frequency. The electrode layer (350) also incorporates a structure (390, 400 ) for modulating a second signal generated in response to receiving the second component by a first signal generated in response to receiving the first component to generate a modulated signal which is re-emitted as reflected radiation from the tag (300). The presence of the tag (300) is determinable from modulation components present in the reflected radiation, thereby distinguishing the tag (300) from other objects capable of reflecting radiation, but not modulating it.
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