System and Method for Selective Communication with RFID Transponders

Abstract

A system having an RFID transceiver is adapted to communicate exclusively with a single RFID transponder located in a predetermined confined transponder target area. The system includes a magnetic coupling device comprising a magnetic flux generator responsive to a radio frequency input signal and a magnetic field pattern former. The pattern former is configured to collect flux produced by the flux generator and to form a field pattern in the location of the transponder target area. The system establishes, at predetermined transceiver power levels, a mutual magnetic coupling which is selective exclusively for a single transponder located in the transponder target area.

1 . A method of establishing communication between a transceiver and a single RFID transponder located in a predetermined confined transponder target area, comprising: 
 generating a magnetic flux field which varies in response to a radio frequency input signal; and    collecting and forming said magnetic field pattern in the location of said transponder target area; and    establishing at predetermined power levels of the transceiver a mutual magnetic coupling which is selective exclusively for a single transponder located in said transponder target area.    
   
   
       2 . The method defined by  claim 1  including locating in said magnetic flux field a ferrite structure having a gap, said field pattern being formed within and adjacent to said gap.  
   
   
       3 . The method defined by  claim 1  including transporting a web of labels through said target area, at least some of which labels have an RFID transponder, and wherein said method includes printing on said labels.  
   
   
       4 . The method defined by  claim 1  including suppressing electric fields associated with said generating of said magnetic flux field, which fields would otherwise reach said target area.  
   
   
       5 . A magnetic coupling device, comprising: 
 a coil having a first side and a second side;    a magnetic field pattern former; and    the magnetic field pattern former covering the first side of the coil and at least a portion of the second side of the coil.    
   
   
       6 . The magnetic coupling device of  claim 5 , wherein the coil is formed as at least a first trace on a printed circuit board.  
   
   
       7 . The magnetic coupling device of  claim 5 , wherein the magnetic field pattern former has a magnetic permeability of at least 20.  
   
   
       8 . The magnetic coupling device of  claim 5 , wherein the magnetic field pattern former is ferrite.  
   
   
       9 . The magnetic coupling device of  claim 8 , wherein the ferrite is flexible and the ferrite is applied to cover the first side of the coil, around at least a first edge and at least a portion of a second side of the coil.  
   
   
       10 . The magnetic coupling device of  claim 9 , wherein the portion of the second side of the coil that is covered by the ferrite is at least 30 percent.  
   
   
       11 . The magnetic coupling device of  claim 5 , further including a first RF shield covering a first side of the coil.  
   
   
       12 . The magnetic coupling device of  claim 11 , wherein the first RF shield has a loop shape with an open circuit.  
   
   
       13 . The magnetic coupling device of  claim 11 , wherein the first RF shield is coupled to an electrical ground.  
   
   
       14 . The magnetic coupling device of  claim 11 , further including a second RF shield covering a second side of the coil.  
   
   
       15 . The magnetic coupling device of  claim 6 , further including a first RF shield covering the first trace; the first RF shield formed as a second trace on the printed circuit board.  
   
   
       16 . The magnetic coupling device of  claim 5 , further including: 
 at least one capacitor in one of series with the coil for series resonance and across the coil for parallel resonance.    
   
   
       17 . A planar coil printed circuit board magnetic coupling device, comprising: 
 a first trace on the printed circuit board forming the planar coil;    a first RF shield, the first RF shield insulated from and covering a first side of the first trace;    a second RF shield, the second RF shield insulated from and covering a second side of the first trace; and    a magnetic field pattern former covering a first side of the printed circuit board area covered by the first trace and at least a portion of a second side of the printed circuit board area covered by the first trace.    
   
   
       18 . The magnetic coupling device of  claim 17 , wherein: 
 the first RF shield is a second trace on the printed circuit board.    
   
   
       19 . The magnetic coupling device of  claim 17 , wherein: 
 the first RF shield has an open circuit.    
   
   
       20 . The magnetic coupling device of  claim 17 , wherein: 
 the magnetic field pattern former has a magnetic permeability of at least 20.    
   
   
       21 . The magnetic coupling device of  claim 20 , wherein: 
 the magnetic field pattern former is flexible ferrite.    
   
   
       22 . A method for increasing planar selectivity of a magnetic coupling device, comprising the steps of: 
 covering an area of the magnetic coupling device where a magnetic field emanation is not desired with a magnetic field pattern former.    
   
   
       23 . The method of  claim 22 , wherein the magnetic field pattern former has a magnetic permeability of at least 20.  
   
   
       24 . The method of  claim 22 , wherein the magnetic field pattern former is flexible ferrite.  
   
   
       25 . The method of  claim 24 , wherein the flexible ferrite is arranged to cover a first side of the magnetic coupling device, a first edge of the magnetic coupling device and at least a portion of a second side of the magnetic coupling device.  
   
   
       26 . A transponder communication selective module, comprising: 
 a magnetic coupling device partially covered by a magnetic field pattern former; located proximate a media feed path;    the media feed path arranged to carry a plurality of transponders sequentially past the magnetic coupling device.    
   
   
       27 . The apparatus of  claim 26 , further including a printhead arranged to apply indicia upon an outer surface of the transponders.  
   
   
       28 . The apparatus of  claim 26 , wherein the outer surface is a label.  
   
   
       29 . The apparatus of  claim 26  wherein, the magnetic coupling device is formed as at least a first trace on a printed circuit board.  
   
   
       30 . The apparatus of  claim 26 , wherein the magnetic field pattern former has a magnetic permeability of at least 20.  
   
   
       31 . The apparatus of  claim 26 , wherein the magnetic field pattern former is ferrite.  
   
   
       32 . The apparatus of  claim 31 , wherein the ferrite is flexible and the ferrite is applied to cover the first side of the magnetic coupling device, around at least a first edge and at least a portion of a second side of the magnetic coupling device.  
   
   
       33 . The apparatus of  claim 32 , wherein the portion of the second side of the magnetic coupling device that is covered by the ferrite is at least 30 percent.  
   
   
       34 . The apparatus of  claim 26 , further including a first RF shield covering a first side of the magnetic coupling device.  
   
   
       35 . The apparatus of  claim 34 , wherein the first RF shield has a loop shape with an open circuit.  
   
   
       36 . A system for sequentially communicating with a plurality of RFID transponders, comprising: 
 a magnetic coupling device located proximate a media supply path arranged to transport RFID transponders sequentially past the magnetic coupling device;    the magnetic coupling device having a magnetic field pattern former arranged to minimize magnetic flux emanation away from the magnetic coupling device, except through a gap; and    the gap dimensioned to enable inductive coupling with only a single RFID transponder at a time.    
   
   
       37 . A method for selectively communicating with a desired RFID transponder among a plurality of RFID transponders, comprising the steps of: 
 energizing a magnetic coupling device; and    passing the desired RFID transponder through a magnetic flux field generated by the magnetic coupling device;    the magnetic coupling device covered on a first side and at least a portion of a second side by a magnetic field pattern former whereby a magnetic flux field generated by the magnetic coupling device is in an area small enough so that only the desired RFID transponder is energized.    
   
   
       38 . The method of  claim 37 , wherein the magnetic field pattern former is formed from a flexible ferrite material.