Abstract:
An antennae device for reading electronic labels includes passive antennae arranged in the form of an array comprising L lines and C columns. The antennae are located in the array by co-ordinates (i, j), i ranging from 1 to L, j ranging from 1 to C. Each antenna (i, j) is controlled by two control switches, one controlling the antennae located on a line i, the other controlling the antennae located on a column j.

Description:
This disclosure is based upon French Application No. 00/15758, filed on Dec. 5, 2000 and International Application No. PCT/FR01/03833, filed Dec. 5, 2001, the contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   The invention relates to an antenna device for reading electronic labels and a system for reading electronic labels. 
   The field of the invention is that of radio frequency identification or RFID applied in particular to the reading of electronic labels (tags) apposed to objects grouped together in a small area. 
   An electronic label comprises a chip and an antenna, both buried in any support, generally of small size. The electronic label functions according to a contactless mode by means of an input-output interface consisting of the antenna. The antenna is of small size in relation to the dimensions of the electronic label. 
   The electronic label is read (or written to) by a reader which has a reading antenna for effecting an electromagnetic coupling with the electronic label. 
   So that the electromagnetic coupling is sufficient despite the small dimensions of the electronic label antenna, one solution consists of the reader being close to the electronic label. 
   These conditions are not always achievable in practice. 
   Another solution described in patent application WO 97/49076 consists, as shown schematically in  FIG. 1 , of using, between the antenna  10  of the reader  1  and the antenna  20  of the electronic label  2 , an auxiliary passive antenna  30 , sometimes referred to colloquially as a parasitic antenna, which begins to resonate at a given frequency under the action of a radio-frequency signal. When it is thus tuned to the given frequency, this auxiliary passive antenna  30  reinforces the electromagnetic coupling M 1  between the reader  1  and the electronic label  2 , by focusing the electromagnetic illumination of the antenna  10  of the reader  1  onto the antenna  20  of the electronic label  2 . This reinforcement is obtained by electromagnetic coupling M 2  between the antenna  10  of the reader and the auxiliary passive antenna  30  and by electromagnetic coupling M 3  between the passive antenna  30  and the antenna  20  of the electronic label. 
   When it is wished to read numerous electronic labels grouped together in the same reading zone of the reader, it is possible to multiply the passive antennae as described above, but the passive antennae, then close to one another, will mutually interfere with each other. 
   It is also possible to use devices comprising as many active antennae as there are electronic labels. However, this multiplication of the active antennae is expensive since it results in a multiplication of the commands managing the transmission and reception radio frequencies of these active antennae. 
   SUMMARY OF THE INVENTION 
   The aim of the present invention is therefore to make it possible to read numerous electronic labels grouped together in the same reading zone of the area, at a reasonable cost. 
   The object of the invention is an antenna device for reading electronic labels, principally characterised in that the antennae are passive antennae controlled by at least one control means. 
   The antennae are preferably organised in the form of a matrix comprising L rows and C columns and located according to the said matrix by coordinates (i,j), i varying from 1 to L, j varying from 1 to C, and each antenna (i,j) is controlled by two control means, one controlling the said antennae situated on row i, the other controlling the said antennae situated on column j. 
   Each control means advantageously consists of a logic-control analogue switch. 
   According to one embodiment of the invention, the device comprises an indicator light associated with each antenna. 
   The indicator light can be a diode connected and controlled by the switches controlling the said antenna, or a gas ionisation system supplied and controlled by each passive antenna with which it is associated. 
   The device comprising, associated with each passive antenna, a second passive antenna, the indicator light can be a diode supplied and controlled by the said second passive antenna. 
   The invention also relates to a system for reading electronic labels, characterised in that it comprises a reader having at least one antenna and a device as described above. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other particularities and advantages of the invention will emerge clearly from a reading of the description given by way of non-limiting example and with regard to the accompanying drawings, in which: 
       FIG. 1 , already described, illustrates schematically a system of electromagnetic coupling between a reader and an electronic label, reinforced by an auxiliary passive antenna, 
       FIG. 2  is a schematic representation of a matrix of passive antennae according to one embodiment of the invention, 
       FIGS. 3   a ) and  3   b ) illustrate schematically an example of an electronic label integrated in a sample-analysis tube, 
       FIG. 4  depicts schematically a system for reading the electronic label of a tube, 
       FIG. 5  depicts schematically a tube storage rack, 
       FIG. 6  depicts schematically a case of the supply of an indicator light by a second passive antenna. 
   

   DETAILED DESCRIPTION 
   In the case of  FIG. 1 , the passive antenna  30  is continuously in a state of functioning although it resonates only according to the radio-frequency signal transmitted by the antenna  10 . It is not switched according to an on or off mode. 
   In a preferential embodiment of a system according to the invention depicted in  FIG. 2 , the passive antennae  30  are organised in a matrix  3  of L rows and C columns, each of these antennae  30  being located by its coordinates (i,j), i varying from 1 to L, j varying from 1 to C. 
   In  FIG. 2 , each of the coordinates (i,j) locates an antenna  30 , but the matrix  3  may comprise holes, some coordinates (i,j) not locating any antenna  30 . In another embodiment, the passive antennae can also be organised according to a volume. 
   In order to be able to select the passive antenna  30  which it is wished to make able to resonate, each of these passive antennae  30  is controlled by a switch. 
   The system depicted in  FIG. 2  is considered. Each row of passive antennae is controlled by a control means  31   i , preferentially a logic-control analogue switch; each column of passive antennae is controlled by a control means  32   j , also preferably a logic-control analogue switch. Hereinafter, as an example of control means, such logic-control analogue switches will be adopted. Finally, each passive antenna (i,j) is controlled by two switches  31   i  and  32   j . When the switch  31   i  and the switch  32   j  are closed, the passive antenna (i,j) is ready to resonate under the action of the radio-frequency signal transmitted by the antenna  10  of the reader. 
   Thus L+C logic-control analogue switches suffice to control L×C passive antennae instead of the L×C switches a priori necessary. 
   The result is a financial saving which is all the more considerable, the greater the number of passive antennae. 
   An example of an application of the invention to low-temperature storage units for samples for analysis will now be described. 
   During surgical interventions for example, fragments of tissues from organs are taken and then placed in tubes and preserved at very low temperature with a view to their subsequent analysis. 
   So as to identify each tube, the normal marking via a bar code printed on a label is advantageously replaced with an electronic label. This is because normal labels subjected to difficult cryogenic temperature conditions sometimes fall off during the various manipulations of the tubes. 
   As depicted in  FIGS. 3   a ) and  3   b ), this electronic label comprising an antenna  20  is integrated in a module  6  fixed to the tube  5 , for example by injection, or placed in a dish welded to the base of the tube  5 . 
     FIG. 4  depicts a system for reading an electronic label on the tube  5  by means of its antenna  20 : it comprises the antenna  10  of the reader  1  and a matrix  3  of passive antennae  30 . 
   As depicted in  FIG. 4 , the antenna  10  is sufficiently large to be placed around all the tubes  5 . This antenna  10  can be replaced with a smaller antenna which is moved or with several antennae. 
   The matrix  3  comprises a control device  34  for the L switches  31  situated along an X axis and the C switches  32  situated along a Y axis. 
   The tube  5  situated facing the passive antenna  30  located by the coordinates (L,C) will for example be considered. 
   The label on the tube  5  is read by effecting a coupling between the antenna  10  of the reader  1  and the passive antenna  30  located by its coordinates (L,C) and by a coupling between this antenna  30  and the antenna  20 . The passive antenna  30  at (L,C) is used by closing the switch  31   L situated on the X axis and the switch  32   C  situated on the Y axis. 
   Another passive antenna  30  situated at ( 1 , 1 ) for example could just as well have been used for reading the label on the corresponding tube, placed above this antenna  30 . 
   As depicted in  FIG. 5 , the tubes  5  are generally placed in racks  7 . In order to read, by means of the antenna  20 , the electronic labels fixed to the tubes  5 , a matrix of passive antennae  30  can be slid under each rack  7 . Each rack  7  can also include such a matrix. 
   Each rack  7  can also be referenced by means of an electronic label comprising an antenna  20 ′, which can be read by means of a passive antenna  30 ′. 
   In the example which has just been described, a passive antenna  30  is associated with each electronic label. One passive antenna  30  can however be provided for several electronic labels and therefore several tubes  5  in our example. It is possible to group together, for example, 4 or 9 tubes, which will then be in the same electromagnetic field of the same passive antenna  30 . 
   The reading of each of these 4 or 9 tubes will then have recourse to an anti-collision method. Such methods have been developed to enable a contactless smart card reader to resolve the problem which is presented when several cards are presented simultaneously in the field of the reader. 
   In a preferential embodiment of the invention, a device for displaying the passive antennae used is added to the passive antenna device  30 . 
   Where the passive antennae are organised in a matrix, a display matrix is added so as to indicate visually the position (i,j) of the passive antenna used and therefore of the electronic label currently being read or written to. 
   The display matrix consists of indicator lights  33  depicted in  FIG. 4 . The indicator light corresponding to the passive antenna (i,j) comes on when this antenna is activated. 
   The indicator light  33  associated with the passive antenna  30 , consisting for example of a diode (Light Emitting Diode or LED) can be connected and controlled by the two switches controlling the corresponding passive antenna: the diode comes on when the two switches  31   i  and  32   j  are closed. 
   According to another embodiment, the indicator light  33  associated with the passive antenna  30  is not connected to the passive antenna  30 . In a first case, the indicator  33  consists of a gas ionisation system such as neon, supplied and controlled by the radio-frequency signal transmitted by the passive antenna  30 . In a second case, a second passive antenna is associated with each of the passive antennae  30  and the indicator light  33 , consisting for example of a diode, is supplied and controlled by the radio-frequency signal transmitted by this second passive antenna. The second passive antenna is itself controlled by the passive antenna  30  with which it is associated. 
   In the latter case depicted in  FIG. 6 , the display matrix  4  then consists of L×C passive antennae  40 , each of these passive antennae being associated with a diode  33 . An enlargement of a passive antenna  40  is included in this  FIG. 6 ; the transmission of light by the diode is represented by the two arrows. 
   In the example which has just been presented, the electronic label is situated between the reader and the passive antenna; in another configuration, the passive antenna could just as well have been situated between the reader and the electronic label.