WO2005031983A2

WO2005031983A2 - Sheet document provided with an electric circuit

Info

Publication number: WO2005031983A2
Application number: PCT/EP2004/010513
Authority: WO
Inventors: Klaus Finkenzeller
Original assignee: Giesecke & Devrient Gmbh
Priority date: 2003-09-19
Filing date: 2004-09-17
Publication date: 2005-04-07
Also published as: DE10343546A1; WO2005031983A3; EP1668603A2; WO2005031983A8

Abstract

The invention relates to a sheet document (10) provided with an electric circuit (12) for storing security data and with a coupling device for enabling the circuit to contactlessly communicate with an external write/read device. According to the invention, the coupling device contains a number of spatially separated coupling elements (18, 20) for different communications channels. The invention also relates to different methods for processing sheet documents, particularly stacks of sheet documents.

Description

Sheet document with an electrical circuit

The invention relates to a sheet document with an electrical circuit for storing security data and with a coupling device for contactless communication of the circuit with an external read / write device. In particular, the invention relates to the processing of sheet documents in a stack, such as the counting, sorting and checking of banknotes in a stack of banknotes, and a sheet document suitable for this.

Sheet documents in the sense of the invention are in particular security or value documents, such as banknotes, identity cards, passports, Nisa stickers, check forms, shares, certificates, flight tickets, vouchers and the like. The sheet document is at least partially flexible and / or foldable and / or crumplable. In connection with the invention, banknotes are mostly discussed below. As a rule, however, any other sheet document can be provided in the sense of the invention instead of a banknote.

Sheet documents, such as banknotes, are often sensed for processing with considerable effort. For example, conventional bank notes are processed with bank note processing machines and certain features of the bank note, such as graphic or luminescent features, watermarks or holograms, are used with sensors and used for counting, sorting or checking the authenticity of the bank notes. Damaged or soiled banknotes or banknotes with missing security features are often sorted out. When processing a stack of banknotes, the banknotes are first individually and then individually processed by individually passing them through the corresponding sensor or test units.

In order to make the processing of sheet documents easier and / or safer, it has been proposed in DE 101 63 267 AI to provide the sheet document with an electrical circuit and with means for communication with a processing device for the sheet document. During processing, information and / or data is transmitted from the processing device to the electrical circuit or from the circuit to the processing device and at least some of the transmitted information or data is used for processing the sheet document.

Proceeding from this, the object of the invention is to further develop a sheet document with an electrical circuit in such a way that improved, in particular simpler, faster and / or safer processing is made possible compared to the prior art. The invention is also intended to provide a device and advantageous methods for processing a generic sheet document.

This object is achieved by the sheet document, the processing device and the processing methods with the features of the independent claims. Developments of the invention are the subject of the dependent claims.

In a first aspect, the invention builds on the prior art in that the coupling device of the generic sheet document contains several spatially separate coupling elements for different communication channels. The several, ie two or more, preferably At least three, separate coupling elements are set up so that the sheet document has two or more different, ie separate, communication channels. In functional terms, this means that the sheet document has two or more communication channels which are separate from one another and which are separated from one another in particular in the local space or in the frequency space or both in the local space and in the frequency space. The separate communication channels make it possible to simultaneously carry out two or more separate communication processes that take place via two or more spatially separate communication channels and / or take place at two or more different frequencies. When processing the sheet documents according to the invention in a stack, it is not necessary to separate them into individual sheet documents beforehand. The division of the coupling device into a plurality of spatially separated coupling elements also makes it possible to separate the energy and data transmission between the read / write device and the sheet document or the data transmission between different sheet documents in the spatial area and / or in the frequency area. The arrangement and design of the coupling elements can then be optimized to the specific requirements of energy or data communication at the respective transmission frequency.

The coupling device preferably contains first capacitive coupling elements which provide a first communication channel, and also second capacitive coupling elements which provide a second communication channel. The coupling device further preferably contains first capacitive coupling elements which are set up to supply energy to the electrical circuit, that is to say in particular provide a first communication channel, and also second capacitive coupling elements which are set up for data communication from the circuit to the external read / write device. which in particular provide a second communication channel. The first capacitive coupling elements can in particular also be set up for data communication from the external read / write device to the circuit. Alternatively, the second capacitive coupling elements are set up for data communication from the external read / write device to the circuit.

In an advantageous embodiment, the first and second coupling elements are formed by conductive capacitive coupling surfaces. In particular, the coupling device can contain two conductive capacitive coupling surfaces as the first coupling elements and a conductive capacitive coupling surface as the second coupling element, so that a total of three electrodes are provided for coupling between the banknotes and to the read / write device. Designs with more than three electrodes are also within the scope of the invention.

According to another expedient embodiment, the first coupling elements are formed by conductive capacitive coupling surfaces for communication in a low frequency range, in particular below 300 MHz, while the second coupling elements by antennas

Communication in a higher frequency range, in particular above 300 MHz are formed.

The first and second coupling elements are preferably galvanically connected to the electrical circuit. Alternatively, the coupling elements can be inductively coupled to the circuit, as described in detail below. According to a second aspect of the invention, an inductive compensation element connected between the conductive capacitive coupling surfaces is provided in a generic sheet document whose coupling device contains at least two conductive capacitive coupling surfaces. The compensation element can compensate for the negative effect of the capacitive voltage divider, which is formed in a stack by the capacitive coupling surfaces of the individual sheet documents. In particular, with a suitable design of the compensation element, a transfer function with very low damping can be achieved.

In a preferred embodiment of the invention, the sheet document has a strip, in particular a security strip, provided with a conductive, in particular a metallic layer, or patch, which electrically connects the coupling surfaces. The conductive layer of the strip or patch is provided with a structure in order to form an inductive compensation element. Such a design of the compensation element is particularly well suited for working frequencies that are not too high, in particular for working frequencies below about 50 MHz.

According to another preferred embodiment, an inductive compensation element is formed by a planar coil, which is applied galvanically to an insulator layer covering the circuit. The electrical connection of the planar coil to the circuit underneath can take place, for example, through an opening in the insulator layer. To increase the mechanical strength, the entire component (circuit with coil) can be provided with a final passivation based on polyamide.

An inductive compensation element according to a further advantageous embodiment is particularly suitable for use at higher working frequencies. tion formed by a coil realized on the semiconductor material itself. Alternatively, an inductive compensation element can be formed by a conductor loop applied to the sheet document substrate, in particular printed with a conductive material. In an advantageous embodiment, the conductor loop has only a few turns, in particular only half a turn. Such designs of the compensation element are particularly suitable for working frequencies from a few hundred MHz to a few GHz.

According to a further preferred embodiment, an inductive

Compensation element, which is implemented as a coil on the semiconductor material itself, implemented as a planar coil in the so-called "coil-on-chip" technology. A coil and a chip card with such a coil in "coil-on-chip" technology are, for example, from DE 40 34 225 C2 known. In "coil-on-chip" technology, a coil which is provided for electrical contact with an electrical circuit arranged on a chip, for example a semiconductor chip, in particular a silicon chip, is not provided in the form of a separately produced and subsequently applied coil , but the coil is directly integrated on the chip. The "coil-on-chip" coil is manufactured in a process technology that is used to manufacture, for example Conductor tracks or comparable circuit parts on the chip is suitable, e.g. by galvanic application on the chip. According to this embodiment, a coil in "coil-on-chip" technology is used as the compensation element.

In the production of the sheet document described, the conductive capacitive coupling surfaces and the conductor loop are advantageously applied to the sheet document substrate in a common working step, in particular printed on with conductive printing ink. In a third aspect of the invention, in a generic sheet document which contains at least two conductive capacitive coupling surfaces, the conductive capacitive coupling surfaces are electrically connected to a first coupling coil, and the electrical circuit is connected to a planar second coupling coil which is galvanically connected an insulator layer covering the circuit is applied. This enables contactless inductive coupling between the capacitive coupling surfaces and the circuit. The leaf document created according to this aspect of the invention has on the one hand a capacitive coupling to the outside, i.e. communicates with a read / write device or other pieces of leaf document (leaf documents) via the capacitive coupling surfaces, and on the other hand has an internal inductive coupling in which the communication between the electrical Circuit and the capacitive coupling surfaces via two coupling coils.

The circuit and the second coupling coil are expediently arranged on or within the first coupling coil. In order to further increase the magnetic coupling, the first and second coupling coils are advantageously arranged with a common central axis. In particular, it is preferred that the geometric dimensions of the first and second coupling coils essentially match. According to a particularly preferred embodiment, the first and the second coupling coils are stacked one above the other in the vertical direction, ie in a direction perpendicular to the two parallel planes of the two coils, and are arranged with a common central axis, the first and the second coil being further preferred have essentially the same geometrical shape, so that the first and the second coil appear substantially congruent with one another in a view along the vertical direction. The first coupling coil is preferably likewise planar and preferably has only a few turns, in particular only half a turn for high frequencies of over approximately 300 MHz.

In an expedient development, the sheet document has a galvanically separated arrangement of the capacitive coupling surfaces - in particular on a second surface of the sheet document, which is arranged opposite to a first surface of the sheet document on which the capacitive coupling surfaces are arranged - one with a conductive one , in particular a strip or patch provided with a metallic layer, which electrically connects the capacitive coupling surfaces in order to increase the parasitic capacitance between the coupling surfaces to a desired capacitance value. In view of the capacitive coupling surfaces, the strip or patch preferably coincides with at least partial areas of each of the two coupling surfaces, but the strip or patch and the coupling surfaces with one another and the two coupling electrodes are galvanically separated from one another, so that the strip or patch is a first electrode forms a capacitor, which is formed by the capacitive coupling surfaces on the one hand and the strip or patch on the other hand, and the capacitive coupling surfaces form a two-split second electrode of this capacitor.

According to a further aspect, the invention comprises a method for processing a stack of sheet documents, in particular a stack of banknotes, in which the sheet documents have an electrical circuit for storing security data and a coupling device for contactless communication of the circuits with an external read / write device, which have a comprises coupling coil connected to the circuit. The communication of the read / write device with the sheet document stack is carried out according to the invention at an operating frequency which is different from the resonance frequency of the coupling coil connected to the circuit. The communication is advantageously carried out at an operating frequency which is above the resonance frequency of the coupling coil connected to the circuit by at least a factor 2, preferably at least a factor 5, in particular by about a factor 10.

In a further method for processing generic sheet documents, in particular bank notes, energy is transmitted contactlessly from a read / write device to the sheet document via a first communication channel. The contactless data communication (data transmission) from the circuit to the external read / write device is carried out via a second (different) communication channel which is separate from the first communication channel.

According to an advantageous embodiment of the method, the contactless data communication (data transmission) from the external read / write device to the circuit is also carried out via the first communication channel. Alternatively, this data communication can be carried out via the second communication channel.

According to a preferred development of the method, there is contactless data communication between the circuits of different

Sheet documents via the second or a third communication channel.

The communication of different communication channels is carried out in a variant of the method via spatially separated coupling elements of the leaf document carried out. In another variant, the communication of different communication channels takes place at different frequencies. It goes without saying that the two possibilities can be combined so that the communication of different communication channels takes place both via spatially separated coupling elements and at different frequencies. The coupling elements can then be optimized for the frequency used.

According to an expedient embodiment of the method, the transmission (of data and / or energy) of the first communication channel is carried out in a low frequency range, in particular below 300 MHz, and the communication of the second communication channel in a higher frequency range, in particular above 300 MHz.

Another method for processing a stack of sheet documents, in particular a stack of banknotes, the attenuation of which has at least a local minimum as in a predetermined electromagnetic frequency range, is characterized by the following method steps:

a) arranging the stack of sheet documents between a transmitting device and a receiving device,

b) selection of a subrange of the predetermined frequency range,

c) coupling an electromagnetic alternating field of a transmission frequency from the selected partial area into the sheet document stack with the transmission device and determining the energy of the alternating field of documents transmitted with the receiving device,

d) varying the transmission frequency within the selected partial area in order to find at least a local minimum of the attenuation of the sheet document stack, and

e) using the found transmission frequency minimal attenuation as the working frequency for the further processing of the banknote stack.

In this way, a working frequency with particularly low damping can be easily determined, the use of which facilitates further processing. In the method described in step d), the transmission frequency is preferably varied within the selected partial range until at least one local maximum and one local minimum of the attenuation are found. In particular, it can be provided that the transmission frequency in step d) is successively increased or decreased in small steps. The sub-range of the predetermined frequency range is expediently selected within a pass band of the sheet document stack.

The mentioned method is particularly suitable for the processing of such sheet document stacks, the sheet documents of which contain an electrical circuit with conductive capacitive coupling surfaces between which an inductive compensation element is connected, since such stacks typically show a transfer function of an nth order filter, where n is the number of Sheet documents are in the stack, so that the transmission function in the pass band fluctuates in terms of attenuation as a function of frequency between relatively high and relatively low attenuation values. A further method for processing a stack of sheet documents, in particular a stack of banknotes, the damping of which has a number of local minima as in a predetermined electromagnetic frequency range is characterized by the following method steps:

a) arranging the sheet document stack between a transmitting device and a receiving device provided with a load modulator,

b) selection of a subrange of the predetermined frequency range,

c) coupling an electromagnetic alternating field of a transmission frequency from the selected partial area into the sheet document stack with the transmitting device and determining the energy of the alternating field transmitted through the sheet document stack with the receiving device,

d) varying the transmission frequency within the selected partial area in order to find at least two local minima of the attenuation of the sheet document stack,

e) modulating the load modulator with a test frequency and determining the remaining modulation amplitude at the input of the sheet document stack at the transmission frequencies determined in step d) with locally minimal attenuation,

f) determining and selecting that transmission frequency of locally minimal attenuation at which the modulation amplitude determined at the input is maximum, and g) using the selected transmission frequency as the working frequency for further processing of the banknote stack.

This procedure determines an operating frequency with low damping and at the same time a large modulation amplitude (= modulation depth).

In an advantageous development of the method, the transmission frequency in step d) is varied within the selected partial range until at least n local maxima and n local minima of the damping are found, n being greater than or equal to 2. The transmission frequency in step d) is advantageously increased or decreased successively in small steps. The sub-area in step b) is expediently selected within a pass-through area of the sheet document stack.

The described method is particularly suitable for the processing of such sheet document stacks whose sheet documents contain an electrical circuit and a coupling device with a circuit for load modulation. During the further processing of the sheet document stack, data communication from the circuits of the individual sheet documents to a read / write device is carried out at the working frequency.

Another method for processing a stack of sheet documents containing one or more sheet documents, in particular a stack of banknotes, the damping of which has several local minima in a predetermined electromagnetic frequency range, is characterized by the method steps: a) arranging the sheet document stack between a transmitting device and a receiving device provided with a load modulator,

b) selection of a subrange of the predetermined frequency range,

c) coupling a first alternating electromagnetic field of a first transmission frequency from the selected partial area and a second alternating electromagnetic field of a second transmitting frequency, which differs from the first transmitting frequency, from the selected partial area into the sheet document stack with the transmitting device and determining the energy of the alternating field transmitted by the sheet document stack with the receiving device,

d) varying the first transmission frequency within the selected partial area and determining and selecting a first transmission frequency in which the damping of the sheet document stack has an at least local minimum,

e) modulating the load modulator with a test frequency,

f) varying the second transmission frequency within the selected partial range and determining and selecting a second transmission frequency at which the modulation amplitude determined at the input is maximum, and

g) using the selected first and second transmission frequencies as working frequencies for the further processing of the stack of banknotes. The first transmission frequency is set so that the attenuation is minimal, ie the energy transfer in the stack is maximum. The second frequency is set so that the modulation amplitude at the input is maximum. The first transmission frequency, which is set to optimal energy transmission (minimal attenuation), is preferably used for energy transmission and / or data transmission to the sheet documents, that is to say, for example, from a read / write device to the respective bank note. The second transmission frequency, which is set to optimal data transmission capacity (maximum modulation amplitude at the input), is preferably used for data transmission from the sheet documents, that is to say for example for data transmission from a bank note to the read / write device or for data transmission between different bank notes.

The amplitude of the electromagnetic alternating field with the first transmission frequency is preferably at least as large as, preferably greater than the amplitude of the electromagnetic alternating field with the second transmission frequency. Optionally, the amplitude of the alternating electromagnetic field with the first transmission frequency is significantly greater than the amplitude of the alternating electromagnetic field with the second transmission frequency. This is expedient since the energy transmission, for which a larger amplitude is recommended than for the data transmission, is only carried out at the first transmission frequency.

According to a development of the method, at least two local minima of the are varied in step d) by varying the first transmission frequency

Damping of the sheet document stack is determined, the process steps being carried out further: h) after step e) and optionally before or after step f): determining and selecting that first transmission frequency of locally minimal attenuation at which the modulation amplitude determined at the input is maximum, and

i) Using the first transmission frequency selected according to step h) as working frequencies for the further processing of the banknote stack.

According to this development, the first transmission frequency is not only tuned to the fact that the attenuation is minimal, but also to the fact that the modulation amplitude is maximal as a function of the value of the first transmission frequency. As a result, the first transmission frequency at which the energy supply takes place is simultaneously set for the best possible data transmission. In addition, as in the embodiment on which the further development is based, the second transmission frequency is still tuned to ensure that the modulation amplitude is maximum as a function of the value of the second transmission frequency, so that the second transmission frequency is set up for data transmission that is as clear as possible.

The sequence of the process steps can be the given alphabetical one, but can also be selected appropriately in another way.

Optionally, at least one further alternating electromagnetic field of a further transmission frequency, which differs from the first and second transmission frequency, is coupled into the sheet document stack from the selected partial area. Preferably, not only a single further, but a plurality of further alternating electromagnetic fields with different transmission frequencies are coupled into the sheet document stack. The further transmission frequency (s) are preferred, as is the second transmission frequency, used for data transmission from a banknote to the read / write device or for data transmission between different banknotes. One or more of the further transmission frequencies can optionally be selected in accordance with steps f) and g), ie by setting the respective transmission frequency to a maximum modulation amplitude at the input. According to an alternative, the further transmission frequency or at least some of the further transmission frequencies, unlike the second transmission frequency, is intentionally not set to a maximum modulation amplitude at the input or output, so that sheet documents are inside the sheet document stack, for the second transmission frequency with at the input or output of the sheet document stack of maximized modulation amplitude is disadvantageous, yet can successfully transmit data.

According to a further method for processing a stack of sheet documents, in particular a stack of banknotes, in which the sheet documents contain an electrical circuit and a coupling device with a circuit for load modulation, the following method steps are carried out:

a) arranging the sheet document stack between a transmitting device provided with a modulation device and a receiving device,

b) coupling an electromagnetic alternating field of a transmission frequency from the selected partial area into the sheet document stack with the transmitting device, determining the energy of the alternating field transmitted through the sheet document stack with the receiving device, and outputting an output signal corresponding to the determined energy, c) generating an input signal for the modulation device from the output signal of the receiving device, pulses with a defined pulse duration being generated from level changes in the output signal, and

d) supplying the input signal to the modulation device and correspondingly modulating the alternating field generated by the transmission device, as a result of which a load modulation signal generated by the circuit of a sheet document at any point in the stack is fed back to the starting area of the stack.

The data transmission between the electronic circuits of the sheet documents of the stack can thereby be optimized or even made possible over the entire stack length. The pulses in step c) are advantageously generated with a pulse duration that is slightly longer than the time period for switching on the load resistor defined for a load modulator of a sheet document. The duration of a load change is expediently chosen to be longer than the transit time of a signal through the sheet document stack.

The invention also includes a device for processing a stack of sheet documents, in particular a stack of banknotes, in which the sheet documents contain an electrical circuit and a coupling device with a circuit for load modulation. The device contains a transmitting device for coupling an alternating electromagnetic field into an initial region of the sheet document stack, a receiving device for determining the energy of the alternating field transmitted by the sheet document stack and for outputting one of the determined energy. output signal, the transmitting and receiving device being arranged such that the sheet document stack can be inserted between them. The device further contains a modulator device which interacts with the transmitter device and which modulates the alternating field generated by the transmitter device as a function of an input signal, and a signal shaping circuit which interacts with the receiver device and which generates the input signal for the modulator device from the output signal of the receiver device that a load modulation signal generated by the circuit of a sheet document anywhere in the stack is fed back to the initial region of the stack.

In a further aspect, the invention includes a book-like document, in particular a passport document such as a passport with a plurality of interconnected security sheets, of which at least one, preferably each, is designed as a sheet document according to the invention. Such a book-like document is machine-readable and highly secure and can be checked without having to turn the pages of the document. Further exemplary embodiments and advantages of the invention are explained below with reference to the figures. For the sake of clarity, the figures are not drawn to scale and proportion.

Show it:

1 is a schematic representation of a capacitively coupled banknote with chip according to an embodiment of the invention, 2 shows a schematic illustration of a capacitively coupled banknote with chip according to another exemplary embodiment of the invention,

3 shows an equivalent circuit diagram for a stack of capacitively coupled banknotes with an inductive compensation element,

4 shows a read / write device for reading out a stack of capacitively coupled banknotes,

5 shows the course of the damping of a stack of capacitively coupled banknotes as a function of the coupled-in transmission frequency,

6 voltage-time profiles at four points of a stack of capacitively coupled banknotes when load modulation is carried out by a banknote chip of the stack,

7 shows a read / write device with feedback for reading out a stack of capacitively coupled banknotes according to an embodiment of the invention,

8 shows two exemplary embodiments for banknotes with a chip, which have an inductive compensation element, in (a) for the range of lower operating frequencies <50 MHz, in (b) for the range of higher operating frequencies, here for 868 MHz and 2.5 GHz . 9 in (a) to (d) four exemplary embodiments for inductive compensation elements, the elements shown in (a), (c) and (d) corresponding to those in FIG. 8,

10 in (a) a partial view of a banknote with a chip inductively coupled via coupling coils, and in (b) a detailed view of (a),

11 shows a basic circuit diagram for the inductively coupled chip of the banknote of FIG. 10,

12 shows an equivalent circuit diagram for a stack of capacitively coupled banknotes with an inductively coupled chip,

13 shows a simulation of the damping behavior of a stack of N capacitively coupled banknotes with an inductively coupled chip for N = 30, 100 and 200,

Fig. 14 is a schematic representation of a passport book with capacitively coupled security pages according to an embodiment of the invention.

The invention is first explained using the example of processing banknotes in a stack of banknotes.

Figure 1 shows a schematic representation of a capacitively coupled banknote with chip. In the case of the banknote, which is generally designated by reference number 10, a chip 12 with an electrical circuit is applied to a banknote substrate 14, for example cotton paper. The Chip 12 is connected via connecting lines 16 to three large-area conductive capacitive coupling electrodes 18 and 20, which are used for the energy and data transmission between the bank note 10 and a read / write device 22. In the exemplary embodiment, the coupling electrodes 18, 20 are printed on the banknote substrate 14 using conductive printing inks.

In the exemplary embodiment, the two external coupling electrodes 18 are used on the one hand for the energy supply of the chip 12 and on the other hand for the data communication 24 from the read / write device 22 to the chip 12 (hereinafter referred to as downlink). The electrode 20 in the middle is used for data communication 26 from the chip 12 to the read / write device 22 (hereinafter referred to as uplink). In addition, in the exemplary embodiment, data communication between the chips 12 of different banknotes 10 (hereinafter referred to as interlink) is also implemented via this electrode 20. The communication channels with regard to energy and data downlink on the one hand and data uplink and data interlink on the other are thus spatially separated from one another in the exemplary embodiment.

In an alternative embodiment, the data downlink, that is to say the data communication 24 from the read / write device 22 to the chip 12, can also take place via the central electrode 20, so that only the energy transfer is carried out via the outer coupling electrodes 18.

Another exemplary embodiment, in which, in addition to spatial separation, communication channels in the frequency domain are also separated, is shown in FIG. 2. There, additional antennas 32 are applied to the banknote substrate 14 in addition to the chip 12 and a first pair of large-area coupling electrodes 30. The coupling electrodes 30 and the antennas 32 are each electrically connected to the chip 12. The chip 12 is supplied with energy via a capacitive coupling to the read / write device 22, which is implemented by means of the coupling electrodes 30. The data downlink 24 from the read / write device 22 to the chip 12 is also implemented in the exemplary embodiment via the capacitive coupling. The range below 300 MHz is preferred as the frequency range for the capacitive coupling.

The data uplink 26 from the chip 12 to the read / write device 22 is carried out in a higher frequency range, preferably in the range above 300 MHz. The antennas 32 are particularly set up for communication at these higher frequencies. In the exemplary embodiment shown, the energy transmission and the downlink communication 24 take place at a frequency of e.g. 30 MHz, the uplink communication, however, at a frequency of 868 MHz.

The behavior of a stack of N capacitively coupled banknotes in operation can be described by an electrical equivalent circuit. By stacking the banknotes on top of each other, two capacitive coupling surfaces lying one above the other form a capacitance Ck. For the sake of simplicity, banknotes with two capacitive coupling surfaces are considered below. The handling of banknotes with several coupling elements proceeds analogously.

If the coupling device contains two capacitive coupling surfaces, two coupling capacitors are available for each banknote. For the chip 12 on the banknote, the two coupling capacitors appear as a series connection of the individual capacitors, so that only Ck / 2 is effective in the equivalent circuit diagram. When it came to feeding energy into the stack, issued that the available supply voltage decreases rapidly towards the end of the stack. A very high voltage would therefore have to be fed in at the input of the stack in order to be able to provide sufficient energy to operate a chip even at the end of the chain.

In order to improve the energy transfer in the stack, an inductance L _p is therefore connected in parallel to the parasitic capacitance C _p , as shown in the equivalent circuit diagram in FIG. 3. In addition to the banknote 10, further banknotes 10-2, 10-3 and the continuation of the stack are indicated there. The value of the inductance L _p is chosen according to the invention in such a way that the phase angle of the current i 2 generated by the parasitic capacitance C _p is compensated for as far as possible by the inductance within the stack. It should be noted that the banknotes 10, 10-2, 10-3 ... in the stack influence one another, so that the resonance frequency of the elements C _p and L _p in the parallel resonance circuit generally does not correspond to the operating frequency of the stack. Examples of the specific implementation of such an inductance L _p are described in detail below in connection with FIGS. 8 and 9.

FIG. 4 shows a read / write device 40 for reading out a stack 42 of capacitively coupled banknotes 10. While in conventional RFID readers the voltage source and the receiver are operated on the same coupling unit (antenna), in the read / write device 40 there are The voltage or signal source 44 and the receiving device 48 are separated and each connected to the banknote stack 42 via separate coupling units or antennas 46 and 50. Energy and data are coupled into the stack 42 via the signal source 44 at the top. The data sent by the banknotes 10, for example a serial number, is read out by coupling the receiving device 48 to the opposite underside of the stack 42. The signal source 44 and the receiving device 48 can also be equipped with a modulator 52 or a load modulator 56 , whose function and mode of action are explained below. In addition to the receiving device 48 at the end of the stack, a further receiving device 54 can be provided parallel to the signal source 44.

The equivalent circuit diagram of FIG. 3 represents an Nth order bandpass for a stack of N banknotes. The numerically simulated frequency dependence of the attenuation D for a stack with N = 120 banknotes is shown in FIG. 5. As can be seen from the course of the attenuation 60 in FIG. 5, the bandpass formed by the banknote stack has a wide passband 62 in which electrical energy can be transmitted to the individual banknotes 10 with very little attenuation. Outside the passband 62, the damping very quickly reaches very large values. In the exemplary embodiment shown, the frequency range from 10 MHz to 160 MHz is shown, the pass band 62 being approximately 100 MHz wide.

As can also be seen in FIG. 5, the attenuation within the passband exhibits a strongly varying or fluctuating behavior, that is to say there are alternating individual frequencies at which the attenuation has a local maximum 64 or a local minimum 66. The exact location of the local extremes depends on the values of the capacities involved, in particular on the coupling capacitance Ck. The coupling capacitance Ck itself is determined by the size of the coupling electrodes, the properties of the dielectric, which is a mixture of banknote paper and air, and given by the distance between the coupling electrodes, in particular the paper thickness. It goes without saying that the electrical properties of the coupling capacities and thus also the exact position of the individual frequencies with locally maximum or minimum attenuation vary from stack of banknotes to stack of banknotes, since the banknotes in a stack, for example, may not lie exactly on one another, may be dirty or wrinkled, or air pockets can arise between the individual banknotes in the stack.

In order to find a working frequency with the lowest possible damping, a sub-area 68 of the pass-through area 62 of the bandpass filter is now selected before the actual processing of the banknote stack 42. Within this sub-range, the signal frequency of the signal source 44 is increased in small steps starting from the smallest frequency value, and in each case the output voltage supplied by the receiving device 48 at the lower end of the stack is measured as a measure of the energy transmitted through the stack. The step size can be approximately 10 kHz for a width of the subrange of 10 MHz, for example.

This measurement is continued until at least one local minimum 66 and one local maximum 64 of the energy transfer function are clearly identified. It goes without saying that a local minimum of the damping D corresponds to a local maximum of the output voltage output by the receiving device 48 and vice versa. The transmission frequency associated with the determined minimum of attenuation is then used as the working frequency for the actual processing of the stack of banknotes. Another method for determining a suitable operating frequency will now be explained with reference to FIG. 6. In this case, an arrangement is preferably used for data transmission from the chips 12 in the stack of banknotes to a read / write device 40, as shown in FIG. 4, in which the data sent by the individual chips 12 at the end of the stack 42 is read out by a receiving device 48 become. If the chips 12 in the stack carry out load modulation for data transmission, this does not only act in the direction of the exit of the stack and the receiving device 48, but also at the point of feeding, that is, back to the signal source 44.

This is illustrated in FIG. 6, in which a stack of N = 120 capacitively coupled banknotes with a chip was simulated by the corresponding equivalent circuit. In the situation shown, the chip of the banknote carries out load modulation at position i = 80 in the stack (i = 1 ... N). The load modulation can be clearly recognized by the voltage-time profile 74 of this chip. The load modulation can also be detected without any problems at the exit of the stack (curve 76). As the first two curves show, which show the voltage curve at signal source 44 (curve 70) and on a chip in the first third of the stack (curve 72), the modulation signal itself can still be detected at signal source 44.

Such behavior is expressly desired when processing stacks of banknotes, since communication between the chips 12 of different banknotes (interlink) can also take place, which enables, for example, the implementation of effective anti-detection algorithms. For example, by bit-by-bit arbitration of the serial data stream generated by the chips 12, a unique serial number can be transmitted to the receiving device 48 within only one iteration loop. However, it has been found that the transmission behavior of a load modulation signal to the signal source 44 is heavily dependent on the selected operating frequency. For example, at a different operating frequency than selected in FIG. 6, the load modulation of the chip shown above could no longer be detected at the input.

In order to optimize the transmission of the load modulation signal to the signal source 44 and thus to enable the interlink communication, the working frequency according to the invention can be determined as follows before the actual processing of the stack of banknotes.

First, at least two local minima 66 of the attenuation of the energy transmission are determined, as described above in connection with FIG. 5. Preferably, however, a larger frequency range is searched than in the exemplary embodiment described in FIG. 5 in order to determine a larger number of local minima 66 of the attenuation of the energy transmission.

The receiver 48 of the read / write device 40 is equipped for the implementation of this method with a load modulator 56 which simulates the load modulation of a chip 12 in the last position in the stack. The load modulator 56 at the end of the stack is now modulated with a test signal of a test frequency and the modulation amplitude of the test signal remaining at the input of the stack is measured at all of the previously determined individual frequencies of the local minima 66 of the attenuation of the energy transmission.

Then that transmission frequency with locally minimal attenuation is selected as the working frequency at which the signal source 44 still measurable modulation achieved by the test signal a maximum amplitude. At this frequency, low attenuation and a large modulation amplitude are then achieved at the same time.

Alternatively, the working frequency can be determined by feeding in a second signal with a second frequency f2, which is not equal to fl, at the input of the stack, in addition to the transmission signal with frequency fl. If the load modulator 56 is modulated with the test signal f3 at the end of the stack, then both frequencies fl and f2 are also modulated with the test signal f3 at the input of the stack. The frequency f2 is now tuned in a larger range, and the degree of modulation at the input of the stack is measured on the signal f2. A frequency is then selected for f2 at which the degree of modulation reaches a maximum value. The frequency fl is set according to any of the methods described above, i.e. while minimizing the attenuation and / or maximizing the modulation amplitude. For data transmission from chips 12 to reader 40, at least signal f2 modulated by load modulation in the stack, but preferably signals fl and f2 are demodulated. The communication channel with frequency fl is used for downlink communication, i.e. for the transmission of energy and / or data from the read / write device to a respective bank note. Since energy is transmitted at the frequency fl, in order to achieve the best possible energy transmission, the frequency is set to a value of fl that the attenuation of the signal with the frequency fl by the stack of banknotes is minimal. The communication channel with the frequency f2 is used for the

Uplink communication and / or interlink communication used, i.e. for the transfer of data from a banknote to a

/ Reader or between banknotes. So that the data at the frequency f2 are optimally transmitted, the frequency f2 is set to a value of f2 that the modulation amplitude is maximum.

Optionally, for the second communication channel, i.e. used for the transmission of data uplink from a banknote to the reader / writer or interlink between banknotes, in addition to the frequency f2, further frequencies f4, f5, f6, f7 etc. For some of the other frequencies f4, f5, f6, f7 etc., the value of the frequency is set analogously to the value of the frequency f2. The frequency f2 and the further frequency (s) can be set either one after the other or simultaneously. For other of the other frequencies f4, f5, f6, f7 etc., quite the opposite, the frequency is not set to the maximum modulation amplitude at the input, but e.g. set to minimum modulation amplitude at the input. This ensures that banknotes inside the stack of banknotes, where the modulation amplitude happens to be very low when the modulation amplitude at the input or output is maximum, still have a frequency at which they successfully transmit data to the outside, e.g. to the read / write device and / or to other banknotes. In this way, the second communication channel provided for the uplink or interlink communication with its plurality of frequencies f2, f4, f5, f6, f7 etc. offers all banknotes of the stack of banknotes the possibility of sending data.

One possibility of further improving the data communication between the banknote chips of a banknote stack (interlink) will now be described with reference to FIG. 7. As already selected above, it is fundamentally desirable if the individual chips in a stack of banknotes can communicate with one another. This results in particular in the case of very large stacks, for example a stack of banknotes with N = 1000 banknotes However, the problem is that a load modulation, which is carried out by a chip at the end of a stack, is only effective with such a small amplitude at the beginning of the stack, even if the operating frequency is skillfully chosen, that the chips at the beginning of the stack do the load modulation of the chip can no longer detect at the end of the stack. In order to counter this problem, the invention proposes to expand the read / write device 40 from FIG. 4 as shown in FIG. 7. The same elements as in Fig. 4 are provided with the same reference numerals.

The banknotes of the stack are designated by reference numerals 80-1, 80-2, ... 80- (N-2), 80- (N-1), 80-N. A chip 12 of a bank note 82 arranged at any point in the interior of the stack carries out load modulation in the situation shown. In order to make the load modulation signal 90 of these chips detectable for all other chips in the stack, the load modulation signal 92 detected at the end of the stack is fed back to the input of the stack.

For this purpose, the read / write device contains, in addition to the signal source 44, a modulation circuit 52 at the beginning of the stack and a receiving device 48 at the end of the stack. The receiver 48 provides an output voltage 92 proportional to the energy transmitted through the stack. This causes load modulation of a banknote chip 12 in the stack to be output by the receiving device 48 as a modulated voltage 92 which is proportional to the load change 90.

The modulated output voltage 92 of the receiving device 48 is fed to a signal shaping circuit 84 which generates 92 pulses with a defined pulse duration from the voltage changes of the output signal (reference symbol 94). These pulses are with a slightly larger Ren pulse duration generated as the time period for switching on the load resistor defined for the load modulator of a bank note 82. The signal 94 shaped in this way is used to control the modulator 52, which changes the output voltage of the signal source 44 for the duration of a pulse, attenuating in the exemplary embodiment that the resulting signal 96 from all chips in the stack - especially also from the chips on Start of the stack - interpreted as a load modulation signal from a single banknote chip.

It goes without saying that the duration of a load change is selected to be greater than the transit time of a signal through the stack. It is also a matter of course that the temporal arrangement and sequence of the transmitted load and voltage changes represents a sequence of data to be transmitted.

The method described with reference to FIG. 7 is particularly suitable for banknotes with two communication channels at different frequencies fl, f2 and / or in combination with the method for processing banknotes in which two different transmission frequencies fl, f2 are used for two different communication channels , In this case, the signal source 44 outputs two signals with different frequencies fl, f2, both of which are received at the receiving device. The modulated output voltage 92b with frequency f2 of the receiving device 48 is fed to a signal shaping circuit 84 which generates 92 pulses with a defined pulse duration from the voltage changes of the output signal (reference symbol 94). These pulses are generated with a slightly longer pulse duration than the time period for switching on the load resistor defined for the load modulator of a bank note 82. The signal 94 shaped in this way is used to control the modulator 52, which outputs the output voltage with the frequency for the duration of a pulse. The frequency of the signal source is changed so that in the exemplary embodiment it weakens that the resulting signal 96 is interpreted by all chips in the stack - especially also by the chips at the beginning of the stack - as a load modulation signal of an individual banknote chip.

FIG. 8 shows two exemplary embodiments for banknotes with chip 12, which have an inductive compensation element with inductance L _p , as was described above with reference to FIG. 3. 8 (a) shows a design of a banknote for the range of low working frequencies <50 MHz, and FIG. 8 (b) shows a design for the range of higher working frequencies, here for 868 MHz and 2.45 GHz. The compensation elements of FIG. 8 will now be explained in more detail with further reference to FIGS. 9 (a) to (d).

8 (a) and 9 (a) provides a strip 100 or a patch with a metallic coating which is applied to the banknote. The metallic coating of the strip 100 is structured (reference symbol 102) in such a way that an inductance of the desired value L _{p is} formed. The use of such a metal-coated strip offers several advantages. On the one hand, the strip offers a convenient option for contacting the flat electrodes 104. If these are printed with a conductive printing ink, they cannot simply be contacted using conventional methods such as bonding, soldering or flip-chip assembly. In contrast, the strip 100 can be applied to the banknote substrate 14 in such a way that an electrical connection is established between the previously printed electrodes 104 and the strip. Alternatively, the electrodes 104 can also be printed on the substrate after the strip 100 has been applied. Although not expressly shown in the figure, the metallic coating of the strip 100 is interrupted at the installation position of the chip 12, so that a connection point of the chip 12 is electrically connected to a first coating segment and a second connection point of the chip 12 is electrically connected to a second coating segment ,

Another preferred implementation of an inductive compensation element consists in applying a coil 106 to the chip 12 by means of a galvanic deposition process, see FIG. 9 (b). Suitable methods for producing such a “coil on chip” are known. For example, the coil is placed as a planar spiral arrangement directly on the insulator of a silicon chip and is electrically connected to the circuit underneath through openings in the insulator layer. In order to increase the mechanical strength of the entire component ensure, for example, a final passivation based on polyamide is carried out.

While the “coil on chip” structures or structures on a metallized strip or patch are preferably used for working frequencies in the frequency range up to approximately 100 MHz, working frequencies in higher frequency ranges, for example at 868 MHz or 2.45 GHz, can be used two further possibilities can be used to implement an inductive compensation element.

One possibility, as shown in FIGS. 8 (b) and 9 (c), is to realize a coil 108 on the semiconductor material 110 (for example silicon, a-Si, p-Si, organic semiconductors) itself. Such components, known as MEMS (microelectro-mechanical components and systems), are known per se and are used in communication technology, for. B. used in satellite receivers or in UMTS mobile phones. Especially in the frequency range above 500 MHz, the inductance L _p required for compensation can assume very small values. It is known from the construction of radio devices for these frequency ranges that simple conductor loops already have an inductance of a few tens of nH. According to a further embodiment of the invention, as shown in FIGS. 8 (b) and 9 (d), it is therefore provided that a conductor loop 114 made of a conductive material, e.g. B. a conductive ink to apply to the banknote substrate. An additional advantage results from the fact that this conductor loop represents an effective short circuit for voltages with a low frequency, in particular for DC voltage, and thus effectively protects the chip 12 at its inputs against static electricity (discharge sparks).

It goes without saying that a banknote can also be equipped with a plurality of inductive compensation elements in order to allow operation at different working frequencies. For example, the banknote shown in FIG. 8 (b) contains both a coil 108 arranged directly on the semiconductor material for communication at 868 MHz, and a half conductor loop 114 for communication at 2.45 GHz.

Another exemplary embodiment of the invention will now be explained with reference to FIGS. 10 to 12. In the exemplary embodiments described so far, it was assumed that the chips 12 of the banknotes are connected to the large-area capacitive coupling surfaces via galvanic contacting, for example by means of flip-chip assembly. Alternatively, the electrical coupling of the chip to the capacitive coupling surfaces can also take place without contact. FIG. 10 shows in (a) a partial view of a bank note 10 with a chip 12 which is inductively connected to the large-area capacitive citative coupling surfaces 120 is coupled. For this purpose, the coupling surfaces 120 are electrically connected to a coupling coil 122 with inductance L1. The coupling coil 122 can be applied, for example, in terms of printing technology in the same work step as the coupling surfaces 120 and, depending on the desired working frequency, consists of at least half a turn, as shown for example in FIG. 9. Usually, however, a coil with one or more coil turns is used, as shown in Fig. 10 (b).

The chip 12 is provided with a second coupling coil 124, which is galvanically deposited on the chip, with inductance L2 ("coil on chip", CoC). The chip 12 with the second coupling coil 124 is applied to the banknote substrate in such a way that the second coupling coil 124 comes to rest on or within the first coupling coil 122. A particularly good coupling is achieved if the second coupling coil 124 and the first coupling coil 122 are located on a common central axis. The geometric dimensions of the coupling coil 122 are preferably selected such that they are identical to the geometric dimensions of the second coupling coil 124 in order to achieve the best possible magnetic coupling between the two coils.

FIG. 11 shows a basic circuit diagram for the inductively coupled chip of the banknote of FIG. 10. The chip 12 is inductively coupled to the capacitive coupling surfaces 120 via the two coupling coils 124 and 122. Also shown is the capacitance Cpl, which occurs as a parasitic capacitance between the coupling surfaces 120 due to the design. Since the parasitic capacitance cannot be eliminated, it is increased according to the invention by the parallel connection of additional capacitances, for example using a metallized strip or patch, if necessary optimize the electrical transmission behavior in the stack with an adjusted total capacity value.

An equivalent circuit diagram for a stack of N capacitively coupled banknotes 10 with an inductively coupled chip 12 is shown in FIG. 12. A mathematical analysis of the equivalent circuit shown shows very good transmission behavior with regard to energy transmission in the frequency range around 100 MHz. In contrast, in the area of the resonance frequency of the second coupling coils 124 of the chips, which is measured outside the stack at 13.56 MHz, no energy transfer in the stack is possible. This situation is illustrated in Figure 13, which shows the attenuation of a stack with N = 30 (curve 130), N = 100 (curve 132) and N = 200 (curve 134) as a function of frequency from 1 MHz to 1 GHz shows.

It is therefore expedient to use a working frequency for communication with the stack which differs from the resonance frequency of the coupling coils (here 13.56 MHz). For example, in the exemplary embodiment, the working frequency used in the stack is selected to be 10 times greater than the resonance frequency of the CoC. It is clear that transponder chips designed for these frequencies are used.

Claims

Patent claims

1. Sheet document, in particular bank note, with an electrical circuit for storing security data and with a coupling device for contactless communication of the circuit with an external read / write device, characterized in that the coupling device contains several spatially separated coupling elements for different communication channels.

2. Sheet document according to claim 1, characterized in that the coupling device contains first capacitive coupling elements for the power supply of the electrical circuit, and that the coupling device further contains second capacitive coupling elements for data communication from the circuit to the external read / write device are set up.

3. Sheet document according to claim 2, characterized in that the first capacitive coupling elements are set up for data communication from the external read / write device to the circuit.

4. Sheet document according to claim 2, characterized in that the second capacitive coupling elements are set up for data communication from the external read / write device to the circuit.

5. Sheet document according to at least one of claims 2 to 4, characterized in that the first and second coupling elements are formed by conductive capacitive coupling surfaces, in particular that the coupling device as the first coupling elements two conductive capacitive coupling surfaces and contains a conductive capacitive coupling surface as a second coupling element.

6. Sheet document according to at least one of claims 2 to 5, characterized in that the first coupling elements are formed by conductive capacitive coupling surfaces for communication in a low frequency range, in particular below 300 MHz, and the second coupling elements by antennas for communication in a higher frequency range , in particular above 300 MHz.

7. Sheet document according to at least one of claims 2 to 6, characterized in that the first and second coupling elements are electrically connected to the electrical circuit.

8. Sheet document, in particular bank note, with an electrical circuit for storing security data and with a coupling device for contactless communication of the circuit with an external read / write device which contains at least two conductive capacitive coupling surfaces, characterized in that one between the conductive capacitive coupling surfaces switched inductive compensation element is provided.

9. Sheet document according to claim 8, characterized in that the sheet document has a strip or patch provided with a conductive, in particular a metallic layer, which electrically connects the coupling surfaces and the conductive layer is provided with a structuring, in order in this way an inductive compensation element to build.

10. Sheet document according to claim 8 or 9, characterized in that an inductive compensation element is formed by a planar coil which is galvanically applied to an insulator layer covering the circuit.

11. Sheet document according to at least one of claims 8 to 10, characterized in that an inductive compensation element is formed by a coil realized on the semiconductor material itself.

12. Sheet document according to at least one of claims 8 to 11, characterized in that an inductive compensation element is formed by a conductor loop applied to the sheet document substrate, in particular printed with a conductive material.

13. Sheet document according to claim 12, characterized in that the

Conductor loop has only a few turns, in particular only half a turn.

14. Sheet document according to at least one of claims 8 to 13, characterized in that the coupling device a plurality of spatially separated

Coupling elements for different communication channels according to one of claims 1 to 7 contains.

15. Sheet document, in particular bank note, with an electrical circuit for storing security data and with a coupling device for contactless communication of the circuit with an external read / write device which contains at least two conductive capacitive coupling surfaces, characterized in that the conductive capacitive coupling surfaces are electrically connected to a first coupling coil, and that the circuit is connected to a planar second coupling coil, which is galvanically applied to an insulator layer covering the circuit, so as to enable contactless inductive coupling between the capacitive coupling surfaces and the circuit.

16. Sheet document according to claim 15, characterized in that the first coupling coil is planar.

17. Sheet document according to claim 15 or 16, characterized in that the first coupling coil only a few turns, in particular only half

Turns.

18. Sheet document according to at least one of claims 15 to 17, characterized in that the circuit and the second coupling coil are arranged on or within the first coupling coil.

19. Sheet document according to at least one of claims 15 to 18, characterized in that the first and second coupling coils are arranged with a common central axis, preferably that the geometrical dimensions of the first and second coupling coils essentially match.

20. Sheet document according to at least one of claims 15 to 19, characterized in that the sheet document has a strip or patch provided with a conductive, in particular a metallic layer, which electrically connects the capacitive coupling surfaces to the parasitic capacitance between the coupling surfaces to increase a desired capacity value.

21. Sheet document according to at least one of claims 15 to 20, characterized in that the coupling device contains a plurality of spatially separate coupling elements for different communication channels according to one of claims 1 to 7.

22. Sheet document according to at least one of claims 15 to 21, characterized in that an inductive compensation element connected between the conductive capacitive coupling surfaces is provided according to one of claims 8 to 14.

23. The method for producing sheet document according to at least one of claims 1 to 22, in which the coupling device comprises conductive capacitive coupling surfaces, characterized in that the conductive capacitive coupling surfaces are printed on the sheet document substrate with conductive printing ink.

24. A method for producing sheet document according to claim 12 or 13, characterized in that the conductive capacitive coupling surfaces and the conductor loop are applied to the sheet document substrate in a common working step, in particular are printed with conductive printing ink.

25. Method for processing a stack of sheet documents, in particular a stack of banknotes, in which the one or more sheet documents in the stack of sheet documents have an electrical circuit for storing security data and a coupling device for contactless communication of the circuits with an external read / write device, which has one with the circuit connected coupling coil, characterized in that the communication of the read / write device with the sheet document stack is performed at an operating frequency that is different from the resonant frequency of the coupling coil connected to the circuit.

26. The method according to claim 25, characterized in that the communication is carried out at an operating frequency which is at least a factor 2, preferably at least a factor 5, in particular by about a factor 10 above the resonance frequency of the coupling coil connected to the circuit.

27. The method according to claim 25 or 26, characterized in that the sheet document stack is formed from sheet documents according to at least one of claims 1 to 22, or with sheet documents producible according to claim 23 or 24.

28. Method for processing one or more sheet documents, in particular bank notes, each having an electrical circuit for storing security data, in which energy is transmitted contactlessly from a read / write device to the sheet document via a first communication channel, and in which a contactless one Data communication from the circuit to the external read / write device is carried out via a second, different communication channel.

29. The method according to claim 28, characterized in that contactless data communication is carried out from the external read / write device to the circuit via the first communication channel.

30. The method according to claim 28, characterized in that contactless data communication is carried out from the external read / write device to the circuit via the second communication channel.

31. The method according to at least one of claims 28 to 30, characterized in that contactless data communication between the circuits of different sheet documents takes place via the second or a third communication channel.

32. The method according to at least one of claims 28 to 31, characterized in that the communication of different communication channels takes place via spatially separated coupling elements of the sheet document.

33. The method according to at least one of claims 28 to 32, characterized in that the communication of different communication channels takes place at different frequencies.

34. The method according to claim 33, characterized in that the communication of the first communication channel is carried out in a low frequency range, in particular below 300 MHz, and the communication of the second communication channel is carried out in a higher frequency range, in particular above 300 MHz.

35. The method according to at least one of claims 28 to 34, characterized in that the sheet document stack is formed from sheet documents according to at least one of claims 1 to 22, or with sheet documents producible according to claim 23 or 24.

36. Method for processing a stack of sheet documents containing one or more sheet documents, in particular a stack of banknotes, the damping of which has at least a local minimum in a predetermined electromagnetic frequency range, characterized by the method steps:

b) selection of a subrange of the predetermined frequency range,

d) varying the transmission frequency within the selected partial area in order to find at least a local minimum attenuation of the sheet document stack, and

37. The method according to claim 36, characterized in that the transmission frequency in step d) is varied within the selected partial range until at least one local maximum and one local minimum of the attenuation is found.

38. The method according to claim 36 or 37, characterized in that the transmission frequency in step d) is successively increased or decreased in small steps.

39. The method according to at least one of claims 36 to 38, characterized in that the partial area in step b) is selected within a pass-through area of the sheet document stack.

40. The method according to at least one of claims 36 to 39, characterized in that sheet document stacks are processed whose sheet documents contain an electrical circuit with conductive capacitive coupling surfaces between which an inductive compensation element is connected.

41. Method for processing a stack of sheet documents containing one or more sheet documents, in particular a stack of banknotes, the damping of which has a plurality of local minima in a predetermined electromagnetic frequency range, characterized by the method steps:

b) selection of a subrange of the predetermined frequency range,

c) coupling an electromagnetic alternating field of a transmission frequency from the selected partial area into the sheet document stack with the transmitting device and determining the energy of the alternating field transmitted through the sheet document stack with the receiving device, d) varying the transmission frequency within the selected partial area in order to find at least two local minima of the damping of the sheet document stack,

f) determining and selecting that transmission frequency of locally minimal attenuation at which the modulation amplitude determined at the input is maximum, and

g) using the selected transmission frequency as the working frequency for further processing of the banknote stack.

42. The method according to claim 41, characterized in that the transmission frequency in step d) is varied within the selected partial range until at least n local maxima and n local minima of attenuation are found, with n greater than or equal to 2.

43. The method according to claim 41 or 42, characterized in that the transmission frequency in step d) is successively increased or decreased in small steps.

44. The method according to at least one of claims 41 to 43, characterized in that the partial area in step b) is selected within a pass-through area of the sheet document stack.

45. The method according to at least one of claims 41 to 44, characterized in that sheet document stacks are processed whose sheet documents contain an electrical circuit and a coupling device with a circuit for load modulation.

46. The method according to claim 45, characterized in that during the further processing of the sheet document stack, data communication from the circuits of the individual sheet documents to a read / write device is carried out at the working frequency.

47. Method for processing a stack of sheet documents containing one or more sheet documents, in particular a stack of banknotes, the damping of which has a number of local minima in a predetermined electromagnetic frequency range, characterized by the method steps:

b) selection of a subrange of the predetermined frequency range,

c) coupling a first electromagnetic alternating field of a first transmission frequency from the selected partial area and a second electromagnetic alternating field of a second transmitting frequency, which differs from the first transmitting frequency, from the selected partial area into the sheet document stack with the transmitting device and determining the energy of the Sheet document stack transferred alternating field with the receiving device, d) varying the first transmission frequency within the selected partial area and determining and selecting a first transmission frequency at which the attenuation of the sheet document stack has an at least local minimum,

e) modulating the load modulator with a test frequency,

g) using the selected first and second transmission frequencies as working frequencies for the further processing of the stack of banknotes.

48. The method according to claim 47, characterized in that at least one further alternating electromagnetic field of a further transmission frequency, which differs from the first and second transmission frequency, is coupled into the sheet document stack from the selected partial area, preferably a plurality of further alternating electromagnetic fields with different transmission frequencies becomes.

49. The method according to claim 48, characterized in that at least one further transmission frequency is selected in accordance with steps f) and g).

50. The method according to at least one of claims 47 to 49, characterized in that the first transmission frequency is used for energy transmission and / or data transmission to the sheet documents.

51. The method according to at least one of claims 47 to 50, characterized in that the second transmission frequency, and optionally the further transmission frequency or further transmission frequencies, is used for data transmission from the sheet documents.

52. The method according to at least one of claims 47 to 51, characterized in that in step d) by varying the first transmission frequency, at least two local minima of the attenuation of the sheet document stack are determined, and that the method steps are carried out further:

h) after step e) and optionally before or after step f): determining and selecting that first transmission frequency of locally minimal attenuation at which the modulation amplitude determined at the input is maximum, and

53. The method according to at least one of claims 36 to 53, characterized in that the sheet document stack is formed from sheet documents according to at least one of claims 1 to 22, or with sheet documents producible according to claim 23 or 24.

54. Method for processing a stack of sheet documents containing one or more sheet documents, in particular a stack of banknotes, in which the sheet documents contain an electrical circuit and a coupling device with a circuit for load modulation, characterized by the method steps: a) arranging the sheet document stack between a transmitting device provided with a modulation device and a receiving device,

b) coupling an electromagnetic alternating field of a transmission frequency from the selected partial area into the sheet document stack with the transmitting device, determining the energy of the alternating field transmitted through the sheet document stack with the receiving device, and outputting an output signal corresponding to the determined energy,

c) generating an input signal for the modulation device from the output signal of the receiving device, pulses with a defined pulse duration being generated from level changes in the output signal, and

55. The method according to claim 54, characterized in that the pulses in step c) are generated with a pulse duration that is slightly greater than the time period for switching on the load resistor defined for a load modulator of a sheet document.

56. The method according to claim 54 or 55, characterized in that the duration of a load change is chosen to be greater than the duration of a signal through the sheet document stack.

57. The method according to at least one of claims 54 to 56, characterized in that the sheet document stack is formed from sheet documents according to at least one of claims 1 to 22, or with sheet documents producible according to claim 23 or 24.

58. Device for processing a stack of sheet documents containing one or more sheet documents, in particular a stack of banknotes, in which the sheet documents contain an electrical circuit and a coupling device with a circuit for load modulation

a transmitting device for coupling an alternating electromagnetic field into an initial area of the sheet document stack,

a receiving device for determining the energy of the alternating field transmitted by the sheet document stack and for outputting an output signal corresponding to the determined energy, the transmitting and receiving device being arranged such that the sheet document stack can be inserted between them,

a modulator device which interacts with the transmission device and which modulates the alternating field generated by the transmission device as a function of an input signal, and

- A signal forming circuit cooperating with the receiving device, which generates the input signal for the modulator device from the output signal of the receiving device, so that a load modulation signal generated by the circuit of a sheet document at any point in the stack is fed back to the starting area of the stack.

59. Apparatus according to claim 58, characterized in that the signal shaping circuit generates from level changes in the output signal of the receiving device a signal with pulses of a defined pulse duration which is slightly greater than the time duration for switching on the load resistor defined for a load modulator of a sheet document.

60. Apparatus according to claim 58 or 59, characterized in that the duration of a load change is chosen to be greater than the transit time of a signal through the sheet document stack.

61. Book-like document, in particular passport document, with a plurality of interconnected security sheets, in which at least one security sheet and preferably each security sheet is formed as a sheet document according to at least one of claims 1 to 22, or from sheet documents that can be produced according to claim 23 or 24.