| 摘要 |
The invention relates to contactless communication systems between a moving object and a reader, in particular systems in which the moving object is a chip card or an identification tag. To enhance communication security, the card reader transmits, from a radiofrequency transmission antenna separate from the main communication antenna, a disturbance signal having the same frequency and modulation type characteristics as the response signal expected from the card to the reader; the electromagnetic coupling between this separate antenna and the antenna of the reader is, however, such that the latter does not “see” the transmitted disturbance but detects only the response from the card; on the other hand, the environment between the card and the reader sees the response from the card only mixed with the disturbance signal.
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