Antenna for contact-free transmission/reception reading system

Abstract

The invention concerns a reader antenna in a system of identification or of access to a zone with controlled access comprising a reader designed to detect responding electromagnetic signals coming from a contact-free portable object such as an ISO card or a disposable ticket (46), the responding magnetic signals being transmitted by an antenna (48) located in the portable object in reply to the reception of electromagnetic signals transmitted by the reader antenna when the bearer of the portable object presents the portable object in front of the reader. The antenna comprises n groups of turns (20, 22, 24) arranged in series wherein each group of k-1 turns includes a number of Nk-1 turns less than the number of Nk turns of the group of k turns (k ranging between 2 and n) and is spaced apart from the group of k turns by a distance Dk-1 greater than a predetermined value, the turns of all the groups being wound in the same direction.

Description

technical field [0001] The present invention relates to transceiver systems using a reader designed to detect, in response to an electromagnetic signal emitted by an antenna located within the reader, a signal presented by its holder in front of the reader. Electromagnetic signals emitted by portable non-contact objects, and in particular the invention relates to a reader antenna for a non-contact transceiver system. Background technique [0002] Carriers used to identify their holder or to enter controlled access areas, such as public transport networks (such as the RATP metro network or the SNCF metro network in France), are increasingly associated with standard contact bodies (cards or tickets) A different so-called "touchless" technology is featured. [0003] The exchange of information between the non-contact body and the reader is usually achieved by remote electromagnetic coupling between a first antenna housed in the non-contact body and a second antenna located in ...

AI Technical Summary

Problems solved by technology

Unfortunately, in the case of one-off tickets, this antenna can be ergonomically confusing as it only works correctly in the segment of that small loop

In addition, the small loop sets up the normal component of the magnetic field within the reader in phase opposition to the field created by the turns of the antenna, which can cause significant operational inefficiency when an ISO format card is held against the small loop

[0008] Additionally, readers such as those described in the prior art EP 0,776,200 patent or US 4,922,261 patent do not deal with this problem; instead these readers deal with the The problem is to make the mutual inductance with the other antenna zero by setting one of the two antennas in the opposite direction on the winding of the two turns to establish a phase opposite

Unfortunately, this approach does not solve the above problem, because the magnetic field generated in the reader is completely non-uniform

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