Patent Publication Number: US-2006011449-A1

Title: Note, reading apparatus and note identification system

Description:
The invention relates to a note, to a reading apparatus and to a note identification system.  
      To improve the security of banknotes, it is possible to provide electronic chips in such a banknote. Suitable applications are the authenticity check at banks (particularly at a central bank), and especially improving and simplifying the authenticity check in businesses, particularly in businesses in the retail trade.  
      On the basis of the prior art, retail businesses perform an authenticity check on a banknote by irradiating the banknote with UV light. This method is not sufficiently secure against forgery, however, and is therefore a high security risk.  
      [1] discloses a banknote which has a transponder chip containing data for the monetary value and the registration number of the respective banknote. The transponder chip from [1] is equipped with a conventional macroscopic antenna coil into which electromagnetic radiation can be coupled in order to read information stored in the chip.  
      However, the banknote known from [1] is expensive to produce, since the conventionally manufactured transponder chip is cost-intensive on account of its large surface area and on account of the high cost involvement for forming the antenna.  
      [2] discloses a note having at least one semiconductor chip and a capacitive antenna which is connected to the semiconductor chip, the antenna overlapping a conductive layer on the note in order to increase the coupling capacitance.  
      [3] discloses a banknote having an electric circuit which is arranged on or in the banknote and which can send or receive information.  
      [4] discloses a security paper which has a coated foil-like support embedded in it, the support having electronic circuits and antennas.  
      The invention is based on the problem of providing a note which can be produced inexpensively while having a high level of security against forgery.  
      The problem is solved by a note, by a reading apparatus for reading information contained in an electronic chip on a note and by a note identification system having the features based on the independent patent claims.  
      The inventive note contains a support element with the flexibility of paper and an electronic chip on and/or in the support element, and also a circuit monolithically integrated in the chip and a field coupling element which is monolithically integrated in the chip, which is set up to interact with an electromagnetic field and which is coupled to the integrated circuit.  
      The inventive reading apparatus for reading information contained in an electronic chip on a note contains a holding device for holding the note and an electromagnetic radiation source for emitting electromagnetic radiation to a field coupling element on the note, which field coupling element is monolithically integrated in the chip on the note. In addition, the reading apparatus contains a detection device for detecting an electromagnetic signal emitted by the field coupling element on the note and an ascertainment device for ascertaining information contained in the chip on the note from the electromagnetic signal emitted by the field coupling element on the note.  
      In addition, the invention provides a note identification system which has a note having the features described above and a reading apparatus having the features described above for reading information contained in an electronic chip on the note.  
      A basic idea of the invention can be seen as being to provide an electronically readable note, whose central piece is an electronic chip on and/or in a mechanically flexible supple paper support element, with a circuit and a field coupling element (clearly an antenna) in fully monolithically integrated form in the chip. On account of the miniaturized manufacturability of the chip, which can be manufactured particularly using silicon microtechnology, provision can be made for the required chip surface area to be very small. This means that the invention makes it possible to produce an inexpensive note in the region of one Euro cent. With typical production costs for a banknote of ten Euro cents, the inventive note is thus a competitive solution to the problem of electronically readable notes. In comparison with the known authenticity check based on UV light, the inventive note permits improved security against forgery.  
      The invention provides a quick and reliable method for detecting the authenticity of notes, e.g. banknotes. In line with one preferred refinement, an electronically readable chip is implemented in a banknote.  
      To match the implementation of the chip in the note, a reading apparatus is provided for reading such a chip using electromagnetic communication between the field coupling element on the note, i.e. a device for interacting with an external electromagnetic field, and the reading apparatus.  
      During manufacture of the note, the support element with the flexibility of paper is produced using a paper production method, and an identification chip is also incorporated into the paper. The chip can be encased with a protective shell beforehand. Following production of the banknote, the chip can have information read from it and possibly written to it using the inventive reading apparatus, e.g. using high frequency (HF) or ultra high frequency (UHF). Data which can be stored in the chip (e.g. a serial number for a banknote and/or for the chip, a value for a banknote, a security code, etc.) improve the authenticity check on the banknote.  
      Since the inventive chip is preferably contained in the support element with the flexibility of paper, i.e. in a pliable paper material, a sufficiently high level of insulation between the chip and the surroundings is made possible. Electric power can be coupled into the note, particularly by capacitive or inductive means.  
      Preferred developments of the invention can be found in the dependent claims.  
      In the inventive note, the field coupling element may be an antenna. The field coupling element refers particularly to an element which can be used to produce electromagnetic coupling to an external electromagnetic field, i.e. an element which can interact or communicate with such an external electromagnetic field.  
      Clearly, an antenna can be regarded as an electromagnetic LC arrangement in particular, i.e. as a type of electromagnetic resonant circuit. The antenna may be inductance-dominated or capacitance-dominated, depending on whether the dominating influential variable in the LC element is the capacitance C or the inductance L of the antenna.  
      In the case of the note, the field coupling element can be set up for capacitive interaction with an electromagnetic field. Expressed in another way, the field coupling element can be used to couple an electromagnetic field and the associated power into the chip using capacitor coupling, for example between an electrode on the field coupling element and an external electrode on a reader.  
      The field coupling element can have a first metalized region for capacitive interaction with an electromagnetic field. Clearly, such a first metalized region can form one plate of a capacitor which is used to provide the capacitive interaction. The second plate of the capacitor can then be implemented using a reading apparatus based on the invention.  
      The first metalized region can be formed either on the top or on the bottom of the chip.  
      The top of the chip can be defined particularly as that side of the chip on or in which an integrated circuit is formed, i.e. which side is processed (particularly using semiconductor technology). The back or bottom of the chip is thus that side of the chip which is opposite the processed side of the chip.  
      In the case of the note, the field coupling element can have a second metalized region, which is electrically decoupled from the first metalized region, for capacitive interaction with an electromagnetic field.  
      This second metalized region may be provided on the same side of the chip as the first metalized region. In line with this refinement, it is possible, by way of example, for both the first metalized region and the second metalized region to be provided on the front or on the back of the chip and to be arranged at a prescribed distance from one another, for example, next to one another. Possible unwanted interactions between the two metalized regions can be eliminated by providing appropriate field shielding or by providing the metalized regions at a sufficiently great distance from one another.  
      As an alternative to the refinement described, the second metalized region can be provided on the opposite side of the chip from the first metalized region. In line with this refinement, by way of example, the first metalized region can be formed on the front of the chip and the second metalized region can be formed on the back of the chip, or vice versa. Unwanted interaction between the two metalized regions is thus avoided on account of the sufficiently great distance between the two metalized regions and on account of the interposed chip material.  
      In the case of the note, the field coupling element can be set up (as an alternative to or in addition to the capacitive coupling described) for inductive interaction with an electromagnetic field.  
      The field coupling element can have a metalized region for inductive interaction with an electromagnetic field. In line with this refinement, the chip communicates with a reader, for example, by means of coil coupling, so that the reader is provided with a reading coil in this case. The communication element used on the note in line with this refinement is a coil, preferably integrated on the chip, which may be in the form of a planar coil in spiral form, for example. A vertical coil arrangement is also possible.  
      The metalized region can thus be formed as an inductance on one side of the chip, preferably on the front or on the back of the chip.  
      The integrated circuit can have a memory device. The memory device can be used to store data.  
      The memory device may be a nonvolatile memory device.  
      In particular, the memory device may be a rewritable memory device (e.g. an EEPROM, “electrically erasable and programmable read only memory”) or a write-once memory device (e.g. an OTP “one time programmable memory”).  
      The memory device can store at least one of the following pieces of information: a serial number for the note, a value for the note or a security code. By means of communication between the note and the reader, a reader can thus read a serial number for the note, for example, and in this way perform an authenticity check on the note. However, it is also possible for communication to take place in the opposite direction, i.e. for the reader to program information into the memory device on the note. Thus, by way of example, a monetary value account which is coded in the form of encrypted data on the note, may have a prescribed sum of money debited from it by the reading apparatus.  
      The integrated circuit may have at least one of the following components: a cryptography module, a rectifier circuit or a load modulator circuit. The functionality of the integrated circuit is almost arbitrary and can be tailored specifically to a given application. The fact that the inventive note can be provided in miniaturized form means that said components can be implemented as integrated circuit components and hence with a very small surface area requirement. A cryptography module can be used to increase security. A rectifier circuit can be provided in order to convert an input-coupled AC voltage on chip into a DC voltage which can be used to supply power to components on the integrated circuit (e.g. a memory device).  
      The note can be set up as a banknote, as a ticket, as a ski pass, as betting slip, as a share, or as a bill, for example. In these applications, a high level of security against forgery is particularly advantageous.  
      The text below describes refinements of the inventive reading apparatus for reading information contained in an electronic chip on a note. Refinements of the reading apparatus also apply to the inventive note, which interacts with the reading apparatus, and vice versa.  
      The inventive reading apparatus can be provided with a reading electrode and a ground electrode which can have the field coupling element on the note inserted between them. In line with this configuration of the reading apparatus, it is possible for capacitive field coupling elements, in particular, to interact with the reading apparatus by virtue of a respective metalized layer on the note and one of the two electrodes of the reading apparatus clearly forming a capacitor, which allows capacitive coupling of electromagnetic energy into the note.  
      As an alternative or in addition, the reading apparatus may have a reading coil in whose surrounding area it is possible to place the note&#39;s field coupling element. In line with this refinement, it is possible for, in particular, a note with an inductive field coupling element to be read by utilizing inductive electromagnetic coupling between an integrated coil on the note and the reading coil.  
      The electromagnetic radiation source can be set up to emit electromagnetic radiation in the high frequency range or in the ultra high frequency range. In principle, the frequencies used can be chosen arbitrarily, provided that the voltages which then need to be applied to the electrodes for the purposes of reading do not become so high and provided that the frequency intervals used do not overlap frequency intervals which are reserved elsewhere. However, the locally very restricted provision of this electromagnetic radiation, which is limited to the region of a reading apparatus, means that it is also possible to operate at frequencies which are actually reserved for other applications. It is then necessary to prevent the radiation from leaving a surrounding area around the note and the reading apparatus, e.g. using shielding.  
      The refinements of the reading apparatus and of the note also apply to the note identification system.  
      In summary, the invention implements a note and a reader very inexpensively, because it can be done in miniaturized form. It should be noted that the invention also provides a note whose chip is encased by an electrically insulating encapsulation, with the field coupling element being provided outside of the encapsulation.  
      A chip based on the invention may have a thickness of 40 μm and a chip size of 0.1 mm 2  for example, which means that the chip can be produced inexpensively, since only a small amount of semiconductor surface area (e.g. on a silicon substrate) is required. The thickness of a banknote may typically be 100 μm.  
      Exemplary embodiments of the invention are illustrated in the figures and are explained in more detail below. 
    
    
      In the figures:  
       FIG. 1  shows a banknote identification system based on a first exemplary embodiment of the invention,  
       FIG. 2  shows a banknote identification system based on a second exemplary embodiment of the invention,  
       FIG. 3  shows a schematic equivalent circuit diagram from which the capacitive coupling for the banknote identification system from  FIG. 1  can be seen,  
       FIG. 4  shows a banknote identification system based on a third exemplary embodiment of the invention. 
    
    
      Identical or similar components in different figures are provided with identical reference numerals.  
      The illustrations in the figures are schematic and are not to scale.  
      The text below describes a banknote identification system  100  based on a first exemplary embodiment of the invention with reference to  FIG. 1 .  
      The banknote identification system  100  contains a banknote  101  and a reader  102 . The banknote  101  has a paper support  103  as a flexible, pliable and hard-wearing support element and has an electronic chip  104  in the paper support  103 . The chip  104  has a circuit (not shown in  FIG. 1 ) monolithically integrated in it. In addition, the chip  104  has a field coupling element monolithically integrated in it, said field coupling element being set up for capacitive interaction with an electromagnetic field and being coupled to the integrated circuit. The field coupling element or in other words an antenna, is formed from a first metalized layer  105  on a top face of the silicon chip  104  and from a second metalized layer  106  on a bottom face of the silicon chip  104 .  
      The banknote  101  is inserted into a holding region  107  in a reader  102 . The holding region  107  is provided as a gap between a base  108  and a cover  109  for the reader  102 . The base  108  has a ground electrode  111  formed in it, and the cover  109  has a reading electrode  110  formed in it. The reading electrode  110  and the ground electrode  111  are arranged such that when the banknote  101  has been inserted they provide sufficiently good capacitive coupling to the banknote  101 , particularly to the metalized layers  105 ,  106  on the banknote  101 . In this case, the reading electrode  110  and the first metalized layer  105  clearly form a first capacitor, and the second metalized layer  106  and the ground electrode  111  form a second capacitor for the capacitive coupling.  
      The banknote  101  has a thickness of approximately 100 μm, and the chip  104  in the banknote  101  has a length of approximately 300 μm.  
      A memory device which forms part of the integrated circuit on the chip  104  stores the serial number of the banknote, the value of the banknote and a security code for checking of the authenticity of the banknote  101 .  
      Since the chip  104  is insulated from the surroundings, an electric power (which is required for reading the signal and, in particular, provides the electromagnetic power which is required for operating the circuit on the chip  104 ) is input-coupled in capacitive fashion in  FIG. 1 . For this purpose, the banknote  101  is positioned between the two electrodes  110 ,  111 .  
      In line with  FIG. 1 , the reading electrode  110  and the ground electrode  111  are part of the reader  102 . Alternatively, the reading electrode  110  may also be in the form of an electrode of a mobile reader, and the ground electrode  111  may be incorporated in the base  108 .  
      The reading apparatus  102  is set up to read information contained in the electronic chip  104  and contains an electromagnetic radiation source (not shown in  FIG. 1 ) for emitting electromagnetic radiation to the metalized planes  105 ,  106  on the banknote  101  and also a detection device (not shown in  FIG. 1 ) for detecting an electromagnetic signal emitted by the metalized planes  105 ,  106  on the banknote  101 . In addition, the reading apparatus  102  contains an ascertainment device (not shown in  FIG. 1 ) for ascertaining information contained in the chip  104  on the banknote  101  from electromagnetic signals emitted by the metalized planes  105 ,  106  on the banknote  101 .  
      The banknote identification system  100  from  FIG. 1  with the banknote  101  and the reader  102  clearly forms an arrangement comprising two capacitances, namely a first capacitance between reading electrode  110  and the top metalized layer  105  of the chip  104 , and a second capacitance between the back&#39;s metalized portion  106  of the chip  104  and the ground electrode  111 . Alternatively, the back&#39;s metalized portion  106  may also be omitted, in which case the second capacitance is formed from the electrically conductive substrate of chip  104  and the ground electrode  111 . When a suitable alternating field with sufficient amplitude is applied, this sets up an electric voltage between the front of the chip and the back of the chip, this voltage being able to be used to generate the operating voltage for operating the integrated circuit on the chip  104 .  
       FIG. 3  shows an equivalent circuit diagram  300  for the arrangement from  FIG. 1 .  
       FIG. 3  shows that the reading electrode  110  has been put at an electric operating potential  301 , whereas the ground electrode  111  is at the electric ground potential  302 . The reading electrode  110  and the first metalized layer  105  have a first capacitance C 1  formed between them, and the second metalized layer  106  and the ground electrode  111  have a second capacitance C 2  formed between them.  
      The setup of an operating voltage in the chip  104  may be implemented in similar fashion to that in conventional high frequency identification chips (RFID (Radio Frequency Identification Device) transponders). In line with the invention, the methods for interchanging the information between chip  104  and reader  102  may also be in a similar form to those in RFID technology.  
      It should be noted that in the case of the configuration shown in  FIG. 1  the reader  102  contains both the base  108  and the cover  109 , which form a slot  107  into which a banknote  101  can be inserted. Alternatively, a capacitive measuring system based on the invention may be formed from a banknote, a ground electrode integrated in a base and a reader which moves over the banknote. In line with this refinement, only the components above the banknote  101  in  FIG. 1  are part of the reader.  
      The text below gives a few numerical examples to illustrate the relevant electrical variables. At a frequency of 13.65 MHz, the impedance of the two capacitances C 1 , C 2  is 1.3 MΩ in each case. At a frequency of 900 MHz, the impedance of the two capacitances C 1 , C 2  is 20 kΩ in each case. In line with current CMOS technology, a power of 140 μW is required on the chip at a frequency of 13.56 MHz and a power of 9.0 mW is required at a frequency of 900 MHz. The impedance of the chip is in the range between approximately 5 kΩ and 20 kΩ.  
      This estimate relates to a distance of 100 μm between the two electrodes  110 ,  111 . At a greater distance, the voltage U required increases accordingly, i.e. even for a 900 MHz application it will barely be possible to have much greater reading distances than 1 mm. This is important in order for reading of the chip not to be able to take place unnoticed (e.g. through pockets or the like), which reduces the risk of deception.  
      A typical banknote has a thickness of 100 μm, see  FIG. 1 . As a chip dimension, a surface area of 0.1 mm 2  is typically required, which is advantageous for the demanded low price level, and a thickness of 40 μm is proposed. It is thus possible to keep the distance to the respective outer electrode below 100 μm.  
      The chip electrodes can be produced from the top metal layer  105  and the back&#39;s metalized portion  106 . Depending on the doping of the silicon substrate for forming the silicon chip  104 , the back&#39;s metalized portion  106  may also be omitted, in which case the material of the silicon substrate adopts the functionality of the second electrode for forming the second capacitance C 2 . On account of the symmetrical design of the banknote  101 , the orientation of the banknote during reading is of no significance, which increases operating convenience.  
      The chip  104  is provided with a memory device which has either a rewriteable memory (EEPROM) or a write-once memory (OTP). It is likewise possible to enable parts of an EEPROM just for single writing (e.g. by using “TOX fuses”).  
      The text below describes a banknote identification system  200  based on a second exemplary embodiment of the invention with reference to  FIG. 2 .  
      The banknote identification system  200  is formed from a banknote  201  and from a reader  202 . The fundamental differences between the banknote identification system  200  and the banknote identification system  100  are described in more detail below.  
      First, in the refinement shown in  FIG. 2 , the reader  202  is provided independently of the base  108 . In other words, in  FIG. 2 a  banknote  201  is placed onto an arbitrary base  108 , and a reader  202  is arranged above it in such a way that capacitive coupling takes place between the metalized layers  105 ,  106  on the chip  104  and the reading and ground electrodes  110 ,  111 .  
      Another important difference between the banknote identification system  200  and the banknote identification system  100  is that in the banknote identification system  200  both the first metalized layer  105  and the second metalized layer  106  are provided on the top of the chip  104 . As  FIG. 2  shows, the first metalized layer  105  is electrically decoupled from the second metalized layer  106 . In addition, in  FIG. 2  both the reading electrode  110  and the ground electrode  111  are contained in the cover  109  of the reader  202 . When the banknote  201  has been inserted into the holding region  107 , capacitive interaction takes place between the reading electrode  110  and the first metalized layer  105 , on the one hand, and between the ground electrode  111  and the second metalized layer  106 , on the other hand. Unwanted interactions between the reading electrode  110  and the ground electrode  111  or between the reading electrode  110  and the second metalized layer  106  or between the ground electrode  111  and the first metalized layer  105  can be suppressed using suitable shielding.  
      The text below describes a banknote identification system  400  based on a third exemplary embodiment of the invention with reference to  FIG. 4 .  
      The banknote identification system  400  implements inductive coupling between a banknote  401  and a reader  402 .  
      The reader  402  differs from the reader  202  in that the reading of information or the communication with the chip  104  is effected using inductive coupling between a reading coil  403  in the reader  402  and a structured metalized layer as integrated coil  404 .  
      In line with the variant from  FIG. 4 , it is thus possible to replace the coupling capacitor principle described with reference to  FIG. 1  and  FIG. 2  with coil coupling (i.e. inductive coupling). In this case, it is possible to put just one coil on the front (or optionally also just on the back) of the silicon chip  104  if said coil has an appropriate number of windings. This avoids the back&#39;s metalized portion of the chip  104  in  FIG. 4 .  
      In the case of the capacitive coupling shown in  FIG. 1  and  FIG. 2 , the design of the reading and ground electrodes is significant. These electrode surface areas are each larger than the chip surface area, and therefore the electrode parts projecting over the chip deliver a background signal and thus make communication between reader and chip more difficult.  
      For this reason, the reading and ground electrodes are preferably split in the manner of a matrix with a respective suitably chosen base area. The individual matrix elements can be polled serially or in parallel. When a chip is detected on a matrix array, all other matrix elements can be turned off (e.g. temporarily) for the further communication.  
      Even in the case of inductive coupling (see  FIG. 3 ), the coupling factor between the chip coil and the reading coil becomes all the less favorable the larger the reading coil becomes in comparison with the chip dimension. For this reason, a split into a plurality of reading coils is also advantageous in  FIG. 4 .  
      This document has cited the following publications: 
      [1] DE 196 30 648 A1     [2] WO 01/39137 A1     [3] DE 101 63 267 A1     [4] DE 29 19 649 A1