DE102014225492B4 - An RFID tag reader for transmitting a read signal, a method for setting a read signal frequency, and methods for providing compare transfer functions - Google Patents

Abstract

An apparatus for inductively or capacitively transmitting a supply signal having a supply signal frequency comprises a determining means configured to determine a transfer function describing a relationship between a first electrical signal and a second electrical signal of the apparatus for a plurality of supply signal frequencies , The apparatus further comprises comparing means arranged to compare the transfer function with a plurality of comparison transfer functions and to obtain a comparison result indicating a deviation between the determined transfer function and the comparison transfer functions. A selection device of the device is configured to select a selection function from the plurality of comparison transmission functions based on the comparison result, the selection function having a minimum deviation from the transmission function within a tolerance range, and wherein the selection device is further configured to select a selection frequency the transfer function assigned to the selection function has a maximum value within a tolerance range. The apparatus includes adjustment means configured to adjust the supply signal frequency based on the selection frequency.

Description

The present invention relates to an RFID (Radio Frequency Identification) tag reader for transmitting a read signal having a read signal frequency to a method for setting a read signal frequency and to a method for providing comparison transfer functions. The present invention relates in particular to methods for adapting an optimized carrier frequency for energy transmission in inductively coupled systems.

In RFID technology, passive transponders (tags) are preferably used - especially where the distance between the reader and the tag is low (typically less than one meter), a cheap or as small as possible transponder is to be used or where a battery change is not or only consuming is feasible. Passive transponders are usually powered by the radiated magnetic field of the reader coil. Passive sensor transponders transmit measurement data in addition to an identification number and, for example, sit in medical implants requiring wireless communication.

For readers with antenna coils of low to medium quality, the energy range is the limiting factor for the range of transponder systems. This may also apply to transponder systems with very high quality antenna coils when the reader is in a metallic environment. The energy range depends, among other things, on the selected carrier frequency.

The reader and the transponder antenna consist in an inductively coupled transponder system of air or ferrite coils, which together with a capacitor form a parallel or a series resonant circuit. The resonant circuits usually have the same resonant frequency or resonant frequencies lying close to each other. The energy range is dependent on the tuning of the resonant circuits and the carrier frequency.

With changes in the environment of the antenna coil, it is difficult to ensure a stable power supply since the equivalent inductance (s) and the equivalent resistance (s) of the antenna coils are affected. The transponder is usually attached firmly to or in an object or a living being - thus the environment does not change noticeably for the usually kept as small as possible transponder coil. In contrast, the environment changes especially for antenna coils on readers that are used mobile. Difficulties in the power supply of the transponder arise not only by too high a distance of the antenna coils, but can also occur in a strongly varying mutual inductance and detuning and losses in the antenna resonant circuit (es).

Most transponder readers available on the market operate on a fixed carrier frequency derived, for example, from standards such as ISO (International Organization for Standardization) 11785, ISO 14223 or ISO 18000-2. Some readers use adjustable tuning capacity to optimize energy transfer. The adaptation of the tuning capacitance can compensate for inductance changes in a limited range and tune the resonant circuit back to the desired resonant frequency. The tuning capacity consists of a switching array of capacitors that can be interconnected as needed. These switching arrays have very large dimensions for mobile reading devices, in particular in the case of series resonant circuits, since the circuits are designed for high voltages.

Although there are also methods that are designed for the transponder side, it should be noted here that the transponder, as mentioned above, is usually in a stationary environment for which it can already be adapted in the system development phase. By contrast, the mobile reader is used for transponders in different environments and at different distances from the surrounding materials.

From the EP 0 625 832 A1 For example, a method is known with an arrangement of capacitors whose capacitance values are binary-stepped. An algorithm successively approximates the optimal capacitance to maximize the voltage or current of the resonant circuit. This method is disadvantageous because of the physical dimensions and the cost of the required circuit, especially for mobile readers.

An experimental setup of a wireless power transfer (WPT) system employs a correction voltage source that compensates for the voltage across an undesirable imaginary part of the tank impedance when the transmitter oscillator detunes. This solution also requires a lot of hardware design.

Alternatively, natural oscillators can be used to adapt to different environments. This requires control loops, z. B. a PLL (phase-locked loop, phase locked loop) for controlling the carrier frequency.

In EP 0 857 981 B1 A method of a voltage-controlled and phase-locked oscillator with a phase comparator and a filter will be described. The carrier frequency is controlled to the resonance frequency of the antenna impedance.

Out US 2013/0088088 A1 is a WPT system is known, which uses on both sides of the system series resonant circuits. The frequency of the exciter current is regulated at the transmitter to the condition that there is no phase difference between voltage and excitation current at the amplifier output. At the receiver of the WPT system, the voltage across the load is regulated. In the case of overvoltage, this control sets a signal to the transmitter, which sets the transmitter in a burst mode.

Although the methods referenced here can regulate the carrier frequency, they regulate their carrier frequency into the resonance frequency of the antenna impedance. The carrier frequencies set with these methods do not necessarily correspond to the optimum carrier frequencies for energy transmission, for example when detuning the reader oscillator by metallic objects.

A well-known WPT system incorporates a built-in metal detector to safely shut off the system when metal is heated in the vicinity of the receiving device. The metal is detected with a measurement of the quality of the receiver resonant circuit. The transmitter receives the value of a measuring process from the receiver and compares this value with a threshold value. The measurement is carried out by a known method, which balances different voltages in the resonant circuit. The system can detect metal only near the receiver and the receiver must determine the values with a measuring method and send them back to the transmitter.

Out US 7,432,809 a method is known for animal transponders, which detects the presence of a transponder and to optimize the detection of a transponder in the body of the animal by emitting a signal. Here, the reduction of the power transmission is detected by a detection method which is also typically used in metal detectors. Although the method detects losses in the vicinity of the read coil, it can not distinguish whether they are caused by a transponder or by surrounding materials, nor can this method optimize the transmission itself.

In Simulation Methods for inductively coupled sensor system in Varying Environments (Jacobi, Hennig, Kolossa in 8 ^th Conference on Ph. D. Research in Microelectronics and Electronics (PRIME), 12-15 June 2012, pages 255-258) is a simulation approach RFID transponder described.

In Low Frequency Reader Design Approach for Metallic Environment (Jacobi, by Bögel, Grabmaier in Proceedings of 2012 European Conference on Smart Objects, Systems and Technologies - SmartSysTech - June 12-13, 2012, pages 1-6) is an influence of metal on one Circuit impedance described.

It would therefore be desirable to have energy-efficient and flexible energy transmission systems, in particular in the RFID area.

The object of the present invention is therefore to provide an RFID tag reading device for transmitting a read signal with a read signal frequency, a method for setting a read signal frequency and a method for providing comparison transfer functions, so that a high level of electrical energy in the respective variable operating environment is transferable.

This object is achieved by an RFID tag reading device according to independent claim 1, by a method for setting a read signal frequency according to independent claim 24 and a method for providing comparison transfer functions according to independent claim 25 and a computer program according to independent claim 26.

The core idea of the present invention is to have recognized that the above object can be achieved in that a transfer function of the RFID tag reading device can be determined, which describes a current and possibly changing environmental situation of the same well, and that based on the determined Transmission function, a transmission signal frequency can be determined, in which the RFID tag transmitting device, taking into account the environmental situation has a good voltage or energy transfer characteristic, so that a high level of electrical energy is transferable to tags and / or efficient operation of the RFID tag transmitting device is possible.

According to an exemplary embodiment, an apparatus for inductively transmitting a supply signal having a supply signal frequency comprises a determination device that is designed to determine values of a transfer function that describes a relationship between a first electrical signal and a second electrical signal of the device for a plurality of To determine supply signal frequencies. The apparatus further comprises comparing means arranged to compare the values of the transfer function with values of a plurality of comparison transfer functions and to obtain a comparison result indicating a deviation between the determined transfer function and the comparative transfer functions. A selection device of the device is designed to select, based on the comparison result, a selection function from the plurality of comparison transmission function, wherein the selection function has a minimum deviation from the comparison transmission function within a tolerance range. The selection device is further configured to select a selection frequency at which a function (H _E ) assigned to the selection function has a maximum function value or maximum value of a function value within a tolerance range. An adjuster of the device is configured to adjust the supply signal frequency based on the selection frequency. It is advantageous in this exemplary embodiment that the comparison transmission functions can be correlated with predetermined situations or scenarios of the device, for example an RFID tag reading device and / or a wireless energy transmission device (WPT), and a current situation is assigned to a (predetermined) situation or scenario may approximate one of the predetermined situations or scenarios. This allows adjustment of the supply signal frequency such that a high level of energy can be transferred independently of an actual determination of the current situation.

According to a further embodiment, a method for providing comparative transmission functions of a transmission system comprises providing a model of the system which is influenced by a plurality of electrical parameters of a device for inductive transmission of a supply signal. The method includes varying a combination of electrical parameters and simulating the combination-influenced model for a plurality of supply signal frequencies of the device to obtain simulated transmission function values for the plurality of transmission signal frequencies, wherein the transmission function values relate an electrical signal to a first electrical signal describe the second electrical signal of the device and wherein the transfer function values of different transmit signal frequencies belong to a transfer function. The method comprises storing the determined transfer function values and the associated combination of parameters in a memory. The method further includes re-varying the electrical parameters, simulating, or backing up until a plurality of transfer functions are stored in the memory. An advantage of this embodiment is that a change of transfer functions by means of a variation of the electrical parameters for later adjustment of a supply signal frequency based on a modified transfer function of an RFID tag reading device can be stored.

Further embodiments provide methods for setting a read signal frequency of an RFID tag reading device. Further embodiments relate to computer programs.

Further advantageous embodiments are the subject of the dependent claims.

Preferred embodiments of the present invention will be explained below with reference to the accompanying drawings. Show it:

1 a schematic block diagram of an RFID tag reading device according to an embodiment;

2 a schematic block diagram of an RFID tag reading device, the one opposite the RFID tag reading device 1 modified comparison means and a modified selection means, according to an embodiment;

3 a schematic diagram of a transponder system, for example, the RFID tag reading device 1 and a tag located in an area of influence of the RFID tag reader, according to an embodiment;

4 a schematic diagram of a model, the example. The transponder system 3 modeled by transfer functions according to an embodiment;

5a a schematic illustration of the dependencies of the comparative transfer functions of the parameters equivalent resistance, equivalent inductance and mutual inductance according to an embodiment

5b a schematic representation of a number of values that can be obtained for the comparison transfer functions, according to an embodiment;

6 a schematic course of a partial transfer function, wherein the abscissa represents the frequency axis and the ordinate exemplifies an amount of the partial transfer function;

7 an exemplary and schematic representation of an array in which, for example, the transmission signal frequencies to be selected can be stored, according to an embodiment;

8th a schematic flow diagram of a method for setting a read signal frequency of an RFID tag reading device according to an embodiment; and

9 a schematic flow diagram of a method for providing comparative transfer functions of an RFID tag reading device according to an embodiment.

Before embodiments of the present invention are explained in more detail in detail with reference to the drawings, it is pointed out that identical, functionally identical or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that shown in different embodiments Description of these elements is interchangeable or can be applied to each other.

Hereinafter, advantageous embodiments of the present invention will be described with reference to an RFID tag reading device. This is designed to generate an electrical voltage in a transponder device (tag) by means of a supply signal (read signal) and a coupling to the wireless energy transmission, in particular an inductive or capacitive coupling, d. H. to transmit electrical energy (power) to them. The advantageous embodiments of the embodiments can be readily transferred to a wireless power transfer system (WPT system), in which by means of an inductive or capacitive coupling between a device for power supply (power source), a supply signal to one or more consumers is transmitted. In both applications, a tuning of the supply signal frequency, with which the read signal of the RFID tag reading device or the supply signal is transmitted (sent), advantageous to a high match of the supply signal frequency with a frequency at which a transfer function of the system has a high value (Amount) or even a maximum to receive.

In the following, reference will be made to transfer functions of a device, in particular an RFID tag reading device. A transfer function is hereinafter referred to as a ratio between a first electrical signal and a comparable, that is in a dependent, second electrical signal, such as an output variable and an input variable. In simple terms, the dependency can be understood as an influence of a system on an input signal thereof, so that the output signal is obtained based on the system influence from the input signal. The first electrical signal may be a signal which is assigned to a receive variable of the RFID tag reading device, wherein the second signal may be a corresponding variable assigned to a transmitting device. By way of example, this may be an amplifier voltage of the RFID tag reading device (second electrical signal) and a signal (first electrical signal) obtained therefrom by the RFID tag reading device, the received signal being from an environment and / or or a transponder device (tag) is influenced. A ratio between the received signal and the transmitted signal or the electrical variable associated with the signals enables a transmission function of the reading device or the transponder system to be obtained. The electrical signals can be voltage signals, current signals or power signals. Embodiments described below allow use of transfer functions based on similar signals, such as when both electrical signals are voltage signals or based on various signals, such as when one of the signals is a voltage signal and one of the signals is a current signal.

1 shows a schematic block diagram of an RFID tag reading device 10 with a transmitting device 12 and a receiver device 14 , The transmitting device 12 and the receiver device 14 can also act as a common facility 15 be arranged for emitting and receiving a magnetic or electric field. The transmission and reception can be carried out by means of a coupling for wireless energy transmission, which can be designed as inductive coupling and / or capacitive coupling. Is the device 15 For example, designed as a resonant circuit for capacitive or inductive coupling, the device can 15 also the antenna 18 with include. The antenna 18 can, for example, as a transmitting coil or capacitor plate of the device 15 be executed to the inductive or capacitive transmission of the read signal 22 to enable.

The transmitting device 12 is designed to receive an electrical signal 16 to provide that to an antenna 18 in the form of a read signal 22 is sent out. The electrical signal 16 may, for example, be a drive signal, which is designed to excite a resonant circuit with a transmitting coil. In an environment of the RFID tag reader 10 arranged transponder devices (tags) and / or metallic objects lead to an influence on the read signal 22 so that at the RFID tag reading device 10 a modified read signal 22 ' is superimposed or preserved. From the superimposed signals can from the receiver device 14 a wired signal 24 to be provided. Although the read signal 22 and the modified read signal 22 ' when two signals are shown, the signals 22 and 22 ' also as the read signal 22 be understood, which by an inductive coupling with a tag and / or a coupling with a metallic object to the modified read signal 22 ' is changed. For example, a tag may be configured to receive the read signal 22 to modulate and / or to the read signal 22 To withdraw energy.

The RFID tag reader 10 includes a detection device 26 which is adapted to provide a transfer function H _M between the electrical signal 24 (second electrical signal) and the electrical signal 16 (first electrical signal) to determine. The determination device 26 is configured to determine transfer function values H _M (f) for a number NF of transmission signal frequencies, such as by providing a control signal 28 to the transmitting device 12 , The number NF may be influenced by a size of the frequency range to be considered within which an adaptation of the transmission signal can or should take place and, for example, comprise a number of at least 3, at least 5 or at least 10 transmission signal frequencies at which (frequency-discrete) the transmission function values H _M (f) can be determined. The transfer function H _M can take place by means of a combination (stringing together) of the transfer function values H _M (f).

The RFID tag reader 10 further comprises a comparison device 32 which is _configured to have the transfer function H _M and / or the transfer function values H _M (f) or amounts thereof with a plurality of comparison transfer functions H _Sx or (absolute) values H _Sx (f) of the comparative transfer functions H _Sx relative to the transfer function H _M comparable frequency points to compare. The comparison may be made with respect to values or a range of values that includes the supply signal frequencies within which the device 10 is adjustable. Alternatively, the comparison can also be carried out with respect to all detected values of the determined transfer function H _M. In simple terms, the comparison can be carried out for the entire determined transfer function H _M or for a subarea thereof. The comparison can be made, for example, by a difference or quotient formation, for example of values or magnitude values between the transfer function H _M and the comparison transfer function H _Sx for some or each of the LF transmit signal _frequencies f. A (total) deviation between the transfer function H _M and one or more of the comparative transfer functions H _Sx can be described, for example, the quality function and / or as the sum of the quotients or differences of the function values. The comparison transfer functions H _Sx may be _stored as a plurality of points or as a continuous function (mapping _rule ).

The comparison device 32 is adapted to calculate the deviation between the transfer function H _M and one, several or each of the comparison transfer functions H _S or the values of the functions as the comparison result 34 a selection device 36 provide. The comparison result may, for example, be a quality function that is created based on the comparison or the comparisons. The selection device 36 is designed to be based on the comparison result 34 or the comparison results 34 select a selection function H _S from the plurality of comparison transfer functions H _Sx . This can be done, for example, by means of a later-described optimization of the quality function. Within a tolerance range, the selection function H _S has a minimal deviation from the transfer function H _M relative to the other comparison transfer functions H _Sx . The tolerance range can have an absolute or relative value. By way of example, an absolute value can be understood as _meaning that the selection function H _{S is} that of the comparative transfer functions H _{Sx which} has the minimum distance to the determined transfer function H _M among the considered comparison transfer functions. As a further relative tolerance range, for example, a tolerance range of 20%, 10% or 5% can be understood, which has the deviation of the comparison transfer function H _Sx with respect to the transfer function H _M.

The selection device 36 is designed to select a selection frequency f _Opt at which a transfer function associated with the selection function H _S , which describes, for example, the energy transfer to the transponder, has a maximum value within the tolerance range. The maximum value may, for example, relate to a function value or an absolute value. As it relates to 4 is explained, an overall transmission system can be understood as a combination of partial transmission functions, wherein one of the partial transmission functions describes the energy transmission from the RFID tag transmission device to the tag. The energy transfer may relate to the transmission of an electrical voltage, an electrical current and / or an electrical power. An energy transfer function can be determined from a ratio between two similar energy quantities but also a ratio between two different energy quantities. Thus, for example, an energy transfer function and / or a total transfer function, which is influenced by the energy transfer function, a ratio between two voltages, such as an output voltage in relation to an input voltage of a (sub) system but also any other ratio of a current to a voltage or power, a voltage to a current or a power and / or a power to a current or a voltage.

This partial transfer function may be determined during a system design depending on various system parameters and in the selector 36 be deposited, such as in a memory. The comparison transfer functions H _Sx and the partial transfer function are influenced by the environment of the RFID tag transmission device and can be assigned to one another, for example via parameters of the influencing or the system change, or can be regarded as belonging to one another. This means that each energy transfer function between RFID tag transmitting device and transponder-describing energy transfer _{function is} assigned a comparison transfer function H _Sx . Based on the determination of a total transfer function of the system, a state of the partial transfer function may be inferred, with system adaptation based on the state of the partial transfer function. In simple terms, the transmitted transfer function H _{M describes} an influencing state of the RFID tag reading device 10 , The selection device 36 is _designed to select that comparative transfer function H _Sx which describes this state of influence approximately or as well as possible within the tolerance range explained above.

The RFID tag reader 10 includes an adjustment 38 configured to adjust the read signal frequency based on the selection frequency f _Opt , such as by means of a control signal 42 to the transmitting device 12 or any other signal suitable for setting the frequency.

By selecting the selection frequency f _Opt and the corresponding setting of the transmission signal frequency to the frequency f _Opt , the RFID tag reading device is set to receive the read signal 22 within a frequency tolerance range with the selection frequency. The frequency f _Opt (selection frequency) may be a frequency supplied by the RFID tag reader 10 is adjustable so that the frequency tolerance range of the selection frequency is 0 or about 0. The frequency f _Opt can deviate from a theoretical (approximately mathematically determinable) optimum transmission frequency, for example when a signal generator for generating a signal with the corresponding frequency is a digital signal generator with discrete frequencies and the theoretical frequency is arranged between two discrete frequencies , That means the read signal 22 can be sent out with the frequency at which an energy transfer from the RFID tag reading device 10 towards a tag and / or influencing the RFID tag reading device 10 is minimal by surrounding metallic objects, or a level of transmitted electrical energy is high to maximum.

The comparison transfer functions H _Sx may, for example, be provided in the form of function values for the RFID tag reading device 10 adjustable read signal frequencies stored in a memory. Alternatively, the comparison _transfer functions H _Sx may be _stored as a function (mapping) of the frequency be. The partial transfer function may have a maximum at a frequency (the frequency f _opt ) that is different than an adjustable transmit signal frequency. The frequency tolerance range may then be within a range of 30%, 20%, or 10% of a frequency value at which the functional maximum is located, and / or the transmit signal frequency of the RFID tag reading device which is the least frequency spaced apart from the particular functional maximum of the partial transmission function having.

In simple terms, the RFID tag reading device allows an adaptation of the transmission signal frequency with respect to a frequency at which a transmission function, which the transmission from the reading device to a tag or from a power source to a consumer) has a high or maximum value. This makes it possible to obtain an efficient energy transfer and differs from known concepts in that they are designed to set the frequency of the transmitted signal to the frequency of the maximum of a total transfer function or to a resonant frequency which, on a frequency of, if necessary, by a transponder or surrounding material influenced transmitting loop or based this corresponds.

The determination device 26 , the comparison device 32 , the selection device 36 and / or the adjustment device 38 may be implemented as a hardware circuit or, alternatively, at least partially in software, ie, as program code executable by, for example, a processor, field programmable gate array (FPGA), or the like.

2 shows a schematic block diagram of an RFID tag reading device 20 that is one opposite the RFID tag reading device 10 modified comparison device 32 ' and a modified selection device 36 ' having. The comparison device 32 ' includes a memory 44 which is _adapted to store the comparison transfer functions H _Sx or their values. Further, the parameter values correlated with the respective comparison transfer function are in the memory 44 saved. The parameter values relate to electrical parameters of the transponder system, such as an equivalent resistance, a replacement inductance and / or a mutual inductance, between the RFID tag reading device 20 and one day, wherein the parameters are from an environment of the transponder system and optionally the coupling between the RFID tag reader 20 and the day are affected. A combination p of parameters can each be assigned to a comparison transfer function H _Sx . A comparison result 34 ' may comprise a deviation between the respective comparison transfer function and the determined transfer function H _M as well as the respective parameters of the comparative transfer function H _Sx , where p describes the combination of the electrical parameters, for instance in the form of a vector.

One opposite the selection device 36 modified selection device 36 ' the RFID tag reading device 20 is _configured to select the selection _frequency f _Opt based on the combination p of parameters associated with the selection function H _Sx . This includes the selection device 36 ' a memory 46 in which information regarding an assignment of a transmission frequency to be selected is stored as a function of the respective parameter set p, which is shown as a function of the selection frequency f _Opt of the combination p of the parameter values (f _Opt (p)).

An assignment of the selection frequencies f _Opt (p) to parameter sets, ie to combinations p of electrical parameters, enables an estimation of the current state of the RFID tag reading device based on the electrical parameters, which allows a precise modeling of the RFID tag reading device 20 allows. In the store 46 Furthermore, information relating to the transfer functions H _Sx associated _{Teilübertragungsfunktionen} (energy transfer functions) H _E are stored. The energy transfer functions H _E are also dependent on or associated with the combinations p of the parameters. The information may, for example, be the frequency at which the energy transfer function associated with the comparison transfer function has the maximum value, so that this frequency can be selected as the selection frequency f _Opt . The electrical parameters can affect a variety of electrical properties of the device 20 Respectively. Is the device 20 trained to the supply signal 22 can emit inductively, the electrical parameters, for example, to a replacement resistance of the device 20 and / or a transmitting coil thereof, a Ersatzinduktivität and / or a mutual inductance, which from an environment of the device 20 acts on this, relate. Is the device 20 trained to the supply signal 22 Capacitive send, so the electrical parameters can, for example, to a replacement resistance of the device 20 and / or a coupling capacitor thereof, a Ersatzinduktivität the coupling capacitor and / or a counter-capacity, which from an environment of the device 20 acts on this, relate. The coupling capacitor can be understood, for example, as a capacitor plate, which enables energy transfer with a correspondingly arranged capacitor plate of a device to be coupled.

3 shows a schematic equivalent circuit diagram of a transponder system 30 , for example, the RFID tag reading device 10 or as transmitting device and receiver device 14 trained facility 15 to send and receive a magnetic or electric field and a day 48 located in an area of influence of the RFID tag reading device 10 is included. The transponder 48 is simplified as a parallel resonant circuit comprising an inductance of a coil 52 (S _T), a capacitance (condenser) 54 (C _T ) and one parallel to the capacitor 54 and the coil 52 arranged resistance 56 (R _C ) executed. The transponder 48 may also have any other components for operating the same. The transponder 48 is inductive with the RFID tag reading device 10 coupled, so that from this a voltage U _T in the coil 52 is induced by starting with a rectifier (not shown) an operating voltage for the transponder chip can be obtained. The transponder can be installed (arranged) in a metallic housing, for example for medical applications.

The RFID reader 10 includes a transmitting coil 58 (S _L ), a spare resistor 62 (R _I ) and a capacitive voltage divider 64 , The transmitting coil ( 58 ), the equivalent resistance 62 and the capacitive voltage divider 64 are interconnected to a series resonant circuit. The capacitive voltage divider 64 includes a first capacitor 66 (C _R ), which is parallel to two series-connected capacitors 68a (C _D1 ) and 68b (C _D2 ) is interconnected. At the capacitive voltage divider is for example at or parallel to the capacitor 68b a voltage U ' _Rec tapped by a measure of an inductive coupling from the coil 58 towards the coil 52 and / or to metallic objects 72 in an environment of the RFID tag reader 10 is affected. Alternatively, the voltage can also be applied to another capacitor (tuning capacitor) 66 or 68a to be obtained. A division of the capacitor 66 decreasing voltage allows lower signal amplitudes and protection against override of receiver or measuring circuits.

Is the metallic object 72 arranged adjacent to the RFID tag reader, may be part of the coil 58 generated field voltages in the metallic object 72 induce and can cause eddy currents there, so that an energy of the field is reduced. An approximation of the metallic object 72 can be determined, for example, by means of the voltage U ' _Rec , if this is based on the presence and / or approach of the metallic object 72 changes. Between the voltage (signal) U ' _Rec and the voltage (signal U _R ), a transfer function can be determined.

The influencing may be frequency-selective, so that the corresponding transfer function between the two signals of the voltage U _R and the voltage U ' _Rec at different frequencies may have different values and / or different amounts and / or so that the influencing at different frequencies different or different can cause strong effects on the transfer function.

In other words shows 3 an inductively coupled transponder system, which is represented by means of an equivalent circuit diagram.

Although the detection of the first electrical signal for determining the transfer function has been previously described as the voltage U ' _Rec across the capacitor 68b is detected, the parameter estimate can also be based on another voltage signal, such as a third capacitor in the voltage divider or by means of a tapped in coil voltage U _L at the transmitting coil 58 , at a resistance of the institution 15 or the transmitting device 12 , About a voltage U _RI , which drops at a series resistance of the resonant circuit, take place. Alternatively or additionally, a transfer function H _{M can} also be detected on the basis of an impedance measurement. Alternatively, another signal correlated with the voltage U ' _Rec may be used to obtain or determine the transfer function, such as a coil current I _L , a voltage drop across the coil 58 or the resistor R _I , an inductively detected coil voltage, a coil voltage which is detected by means of a capacitively coupled capacitor plate, or a power signal, and a second electrical signal suitable for this purpose. The current I _L , for example, correlates with the voltage U _R when it is applied. Alternatively, it correlates voltage U _R with the current I _L when the current I _{L is} impressed. Includes the facility 15 a current source, a (total) transfer function can be easily formed by using the current I _L , such as by forming a ratio U _R / I _L. This in 3 described embodiment uses the receiver voltage across the capacitor C _D2 ( 68b ), since this can be tapped in many RFID tag readers in a simple manner, that is present anyway. This voltage can be used, for example, for data detection. It goes without saying that a large number of further electrical energy quantities can be used to obtain the overall transfer function. It is understood further. that the energy quantities can be designed to differ in exemplary embodiments. Includes the facility 15 For example, a parallel resonant circuit, which is about the coil 58 and the capacitive voltage divider circuit connected in parallel therewith 64 has, so can the Current I _L flowing through the coil may be different from a current provided by a current source (not shown) and feeding the parallel resonant circuit.

4 shows a schematic diagram of a model 40 , eg the transponder system (complete system) 30 modeled using transfer functions. The model 40 includes a total transfer function 74 (H _G ), which is a ratio of an environment-influenced voltage U _Rec and an affected voltage U ' _Rec with respect to the drive signal 16 (U _R ) describes. For example, U _R denotes the voltage at an amplifier output of the transmitting device 12 , For the receiving branch of the reader, the voltage U _Rec in a series resonant circuit, as in 3 is shown, for example via a tuning capacitor 66 (C _R ) tapped and divided down if necessary, so as not to override the recipient. The voltages U _Rec or U _Rec 'can, for example, the first electrical signal 24 be, which is used to determine the transfer function. The transfer function H _M determined may, for example, the overall transfer function H _G correspond, so that the transfer function H _M may correspond to the measured value of the modeled overall transfer function H _G.

A total transfer function 74 (H _G ) is based on three partial transfer functions 76 (H _SP ), 78 (H _E ) and 82 (H _D ), the context of which is explained below. H _SP denotes a so-called superposition transfer function which describes a voltage transfer from an amplifier output on the RFID tag reading device to a first part (U _Rec1 ) of the voltage U _Rec at the receiver tap of the RFID tag reading device.

H _E denotes a so-called energy transfer function, which here describes a voltage transfer from the amplifier output to the RFID tag reading device to the resonant circuit of the transponder and can also be described as a ratio of the voltages U _R and U _T. The energy transfer function HE is in the form of a control signal 84 controlled by the presence, movement and / or operation of the transponder (s). In the absence of the transponder, the energy transfer function H _E can be assumed to be "0". For example, a reduced replacement load resistance results 56 (R _C ) of the transponder or to reduced amounts of the energy transfer function H _e .

H _D denotes a so-called data transfer function which describes a voltage transfer from the resonant circuit of the transponder to a second component U _{Rec2 of} the voltage U _Rec at the receiver _tap of the RFID tag reading device. In this case, the voltage U _{Rec2 is to be} regarded as a mathematical auxiliary quantity, which merely serves for better understanding. The voltages U _Rec1 and U _Rec2 can be added together to form the voltage U _Rec . The voltage U _Rec1 can correspond to the voltage U _Rec if no transponder is active on the RFID tag reading device.

The data transfer function H _D is also influenced by the presence or the operation of the transponder, wherein the energy transfer function H _E as the Hin channel of the reader with respect to the transponder and the data transfer function H _D can be described as a return channel. The two transfer functions H _E and H _D can thus be considered as a series circuit, which is connected in parallel to the superposition transfer function H _SP . The total transfer function H _G can, for example, via the context H _G = H _SP + H _E · H _D to be discribed.

The presence of metallic objects and / or transponders influences the model 40 with respect to the energy transfer function H _E and the data transfer function H _SP . The nature of this influence can be determined in advance, simulated or recorded and stored in the device by means of a comparison transfer function and / or the resulting parameter values.

In simple terms, influencing an environment of the RFID tag reading device based on an influence of the energy transfer function 78 , the data transfer function 82 , the super position transfer function 76 (H _SP ) and / or the resulting influence on the overall transfer function 74 be determined. An adjustment of the transmission signal frequency or a selection of the selection frequency can be based on a maximum of the transmission function 78 . 82 . 76 or 74 or a maximum amount value.

5a shows a schematic clarification of the dependencies of the comparative transfer functions H _Sx of the parameters equivalent resistance R ', Ersatzinduktivität L' and mutual inductance M, each of which is a vector V _R of length NR, V _L of length NL and V _M of length NM summarized. The parameters can be combined as desired to a respective set of parameters, so that there are a number of V possible comparison transfer functions resulting with V = NR × NL × NM. A number NR, NL and / or NM and the values of the entries may be different or equal to each other, for example corresponding to a number of values of the respective parameter to be taken into account in all or all of the values associated with the later application of the system. The number NR, NL and / or NM may, for example, be a value of at least 2, at least 5 or at least 10, alternatively also at least 15.

Alternatively or additionally, the comparison transmission functions can also be influenced by further parameters, so that a comparison with the comparison transmission functions and the determination of the supply signal frequency is based on the further parameters. If, for example, an influence on the transponder coil is taken into account, as can be done based on the mutual inductance M, for example, and if ferrite coils approach each other, this parameter change can also be taken into account. For this purpose, for example, a fourth and fifth parameters can be stored, which describe, for example, an inductance (fourth parameter) and a resistance (fifth parameter) of the transponder coil, so that a combination of the parameters for obtaining the comparative transfer function (s) is also based thereon. If the device is designed to capacitively transmit the supply signal, the fourth parameter may relate to a capacitance and the fifth parameter may relate to a resistance of a coupling capacitor of the receiver device coupled to the device. Such a consideration can alternatively also take place by means of the already existing parameter, in this case the mutual inductance M. According to embodiments, devices for inductively or capacitively transmitting a supply signal, such as an RFID tag reader and / or energy sources of a WPT system, may also be configured to adjust the frequency of the transmitted power signal based on two parameters, such as the equivalent resistance R and the equivalent inductance L, to be determined. The mutual inductance M can, for example, be regarded as immutable or to a non-relevant extent variable and neglected for the determination of the frequency. This makes it possible to determine the frequency to be set with less computational complexity, since the number V, for example, has only a value of NR × NL.

Alternatively, if the transponder 48 or another device is capacitively coupled to the device, the parameter estimation may be based on the capacitor's (spare) capacitance and the replacement (parallel) resistor. Alternatively or additionally, in the case of a capacitive coupling, a counter-capacitance (third parameter), which acts on the device from an environment, can be taken into account in the estimation of the electrical parameters. Alternatively or additionally, the influencing of the transponder described above in the system can be taken into account in the form of the fourth and / or fifth parameter. The fourth and / or fifth parameters may also relate to influencing the capacitances of the capacitive coupled device. In principle, a determination of the supply signal frequency may also be based on a subset, preferably at least two, of the parameters explained above.

As it is in 5b For each of the V comparison _{transmission functions} H _{Sx where} x = 1,..., V, a number of LF values of the respective comparison transmission function may be stored at a respective frequency, where NF is a number of frequency support points and / or possible transmission signal frequencies of the RFID Day reading device corresponds. This means that, for example, a number of V × NF values in a comparison value memory, for example the memory 44 , can be deposited.

6 shows a schematic course of an energy transfer function H _E , which is assigned to a comparison _transfer function H _Sx or selection function, wherein the abscissa represents the frequency axis and the ordinate an amount of the transfer function H _E.

At a frequency f _max , the transfer function H _E and / or its magnitude has a maximum (maximum value) (| H _E | _max ). The maximum value is exemplified as the maximum amount of the energy transfer function H _E , which is a partial transfer function of the associated overall transfer function. Alternatively, it may be another maximum value, such as a maximum function value. Preferably, the maximum value (| H _E | _max ) is a global maximum, at least within the frequency range within which the supply signal frequency is adjusted. The frequency f _Opt can be assigned to the transfer function H _E and / or the parameter values and stored in a memory, for example in the memory 46 , This allows, by means of an estimation of the parameters, the Comparison transfer function H _{Sx are} assigned, the energy transfer function H _E and / or the selected frequency f _Opt can be selected.

Alternatively, the respective frequency f _{Opt can} also be within a tolerance range 86 around the maximum of a respective energy transfer function 78 (H _E ) or their amount may be arranged around, such as when the mathematical maximum does not match a set or adjustable transmission signal frequency of the RFID tag reading device and / or if the energy transfer function 78 (H _E ) is present as a continuous function. The stored and adjustable frequency f _Opt may be, for example, the frequency having the smallest frequency difference to the frequency f _max . The smallest distance can be determined, for example, by means of a difference or a quotient between the two frequencies f _max and f _Opt . Alternatively, the adjustable frequency f _{Opt may be} that frequency at which the magnitude of the energy transfer function 78 (H _E ) as close as possible to the amount of energy transfer function 78 (H _E ) is at f _max .

7 shows an exemplary and schematic representation of an array A _f (p), in which, for example, to be selected transmit signal frequencies f _{opt are} stored, for example in the memory 46 , The three parameters L ', R' and M can be stored in vectors and be understood so that the vectors span a three-dimensional space in which each point p represents a frequency value f _Opt , which _depends on the combination p of the parameters L ' _x , R ' _x and M _x depends.

The selection device can thus be designed to select the selection frequency f _opt to be selected directly on the basis of the determined or estimated parameter set (combination) p.

Alternatively or additionally, the array A _f (p) may also have frequencies which (possibly within a tolerance range) have a maximum, the data transfer function 82 , the super position transfer function 76 or the total transfer function 74 assigned.

In other words, changing environmental influences in a transponder system can lead to a changed proportionality factor between the inductor flux and the generating current, a so-called substitute inductance L ', of the coil generating the induction flux. Similarly, an equivalent equivalent resistance R 'describes the resistance of the wire and any losses resulting from other influences. These influences may be due to the surrounding materials, e.g. B. by conductive materials in which eddy currents occur, or by ferromagnetic materials.

The varying influences of the environment on the antenna resonant circuit on the reader (RFID tag reading device) and thus also the transfer functions of the transponder system can be detected by means of the variable parameters L 'and R' of the reader coil. In general, when the environment on the reader coil is affected, an increase over the initial (uninfluenced) value is possible or expected with the equivalent resistance R ', while an increase as well as a decrease compared to the initial value can occur at the equivalent inductance L'. These changes may cause attenuation and detuning to lower and higher resonant frequencies, respectively, in a single tuned circuit. Furthermore, a third parameter, the mutual inductance M, in particular for mobile readers, can be regarded as variable.

In the presented here novel concept of carrier frequency adaptation, the carrier frequency (read signal frequency) is optimized both at high coupling and at high distances and correspondingly low coupling between the reader and the transponder coil. The model used for optimization (Model 40 ) can map the effects of different environments on an LF transponder system by modifying the variable parameters (eg, L ', R', and M) entering the coefficients of the transfer functions.

For a first simple consideration of the principle, it can be assumed that the transponder resonant circuit (coil 52 , Resistance 56 and capacitive capacitor 54 ) was tuned to an initial resonant frequency f ₀ , taking into account its environment and remains tuned at this frequency.

The reader oscillation circuit is tuned in a neutral environment without further knowledge of the environment in a later reading to the frequency f ₀ or a nearby frequency.

definiert werden, also als Maximum der Energieübertragungsfunktion H_E (Teilübertragungsfunktion). Sie entspricht beispielsweise der Frequenz im Maximum des Betrags der Energieübertragungsfunktion 78 des Modells 40, wobei f_C bzw. f die Menge aller in dem System einstellbaren Trägerfrequenzen umfasst. Mittels des hier vorgestellten adaptiven Verfahrens ist diese optimale Trägerfrequenz f_Opt im Lesegerät ermittelbar, ohne die Spannung U_T im Transponder zu kennen.The optimal carrier frequency (read signal frequency) f _Opt for the system, for example, via

be defined, ie as the maximum of the energy transfer function H _E (partial transfer function). For example, it corresponds to the frequency at the maximum of the amount of energy transfer function 78 of the model 40 where f _C or f comprises the set of all carrier frequencies that can be set in the system. By means of the adaptive method presented here, this optimum carrier frequency f _Opt can be determined in the reading device without knowing the voltage U _T in the transponder.

kann die gemessene Gesamtübertragungsfunktion H_GM, etwa die Übertragungsfunktion H_M, wie sie in 1 beschreiben ist, bei den Frequenzen V_F(nf) aus

ermittelt werden. Das bedeutet, das Signal U_Rec bzw. U'_Rec ist von der Beeinflussung der Parameter abhängig. Der Vektor V_F kann dabei so gewählt werden, dass der Aufwand für die Ermittlung der Koeffizienten und die anschließende Berechnung möglichst gering gehalten wird, und trotzdem alle charakteristischen Merkmale der Gesamtübertragungsfunktion H_G sicher erfasst werden.Since U _{T is} not known, the coefficients of the energy transfer function are also 78 initially unknown. However, knowing the constant parameters and the identification of the parameters designated as variable, the coefficients can be completely determined and thus also the optimum carrier frequency f _Opt . The variable parameters can be in a parameter vector p = [L ' _R R' _R M] will be summarized below. On the reading device, the transmission signal U _R , about the electrical signal 16 , and the received signal U _Rec , about the electrical signal 24 , known. Real or complex values of the total transfer function can be calculated using the real or complex ratio (amplitude and possibly phase information) of the voltages 74 (H _G ) are determined at the respective carrier frequency f. It may alternatively z. B. also made an impedance measurement. The coefficients of the total transfer function H _G are determined for a limited number NF of carrier frequencies that can be stored in a vector V _F. With nF ε {1, ..., NF} ⊂

For example, the measured total transfer function H _GM , such as the transfer function H _M , as shown in FIG 1 at the frequencies V _F (nf)

be determined. This means that the signal U _Rec or U ' _Rec depends on the influence of the parameters. The vector V _F can be chosen so that the cost of determining the coefficients and the subsequent calculation is kept as low as possible, and yet all characteristic features of the overall transfer function H _G are detected safely.

Alternatively or additionally, the total transfer function H _{G can} also be determined by other measures, for example by excitation of the system with band-limited pseudo noises or with a chirp signal. The pseudo noise or chirp signal in the frequency domain can be designed to excite the system at all relevant carrier frequencies. Furthermore, other suitable, known methods can be used, such. B. Method with a pulse-shaped signal.

ein diskretisierter Parametervektor aus den variablen Parametern L', R' und M, der als p_D = [V_L(n_L)V_R(n_R)V_M(n_M)] darstellbar ist. Bei der Berechnung der Koeffizienten bei mehreren Frequenzen kann somit das vierdimensionale Array H_GS mit H_GS(n_F, n_L, n_R, n_M) = H_G(V_F(n_F), p_D(n_L, n_R, n_M)) der Größe NL × NR × NM × NF abgeleitet werden.Advantageously, the method for frequency adaptation in an application can be implemented quickly and in a resource-saving manner. For an estimation of the parameter vector p to be selected, first the model in 4 calculates a four-dimensional array H _GS with simulated total transfer functions, which later in the implementation, ie in the RFID tag reading device, serves the parameter estimation. For this purpose, the three variable parameters are limited to ranges which comprise, for example, a possible or to be considered value range, and which store discrete values in the vectors V _L , V _R and V _M with the respective lengths NL, NR and NM. For each simulation, this results in the variables n _L ∈ {1, ..., NL}, n _R ∈ {1, ..., NR} and n _M ∈ {1, ..., NM}, n _L , n _R , n _M ⊂

a discretized parameter vector from the variable parameters L ', R' and M, called as p _D = [V _L (n _L ) V _R (n _R ) V _M (n _M )] is representable. When calculating the coefficients at several frequencies, the four-dimensional array H _GS can thus be used with H _GS (n _F , n _L , n _R , n _M ) = H _G (V _F (n _F ), p _D (n _L , n _R , n _M )) of size NL × NR × NM × NF.

dargestellt werden. Das bedeutet, dass p_Opt demjenigen Parametersatz aus den Parametersätzen (Kombinationen) p bzw. p_D entspricht, dessen aufsummierte quadrierte Abweichung zwischen dem Betrag der gemessenen Übertragungsfunktion und dem Betrag der Vergleichsübertragungsfunktion, der die jeweilige Kombination p zugeordnet ist, einen minimalen Wert aufweist. Die dargestellte Summenbildung kann bspw. eine von der Vergleichseinrichtung erhalten und als Vergleichsergebnis oder Teil hiervon der Auswahleinrichtung bereitgestellten Gütefunktion erhalten werden. Die Auswahleinrichtung kann basierend auf der erhaltenen Gütefunktion eine Optimierung derselben ausführen, so dass ein Ergebnis der Optimierung die geschätzten Parameter darstellt, bzw. diese basierend auf den ermittelten Ergebnis der Optimierung(-sfunktion) erhalten werden können.With an estimation method, e.g. As the method of least (squares) squares, the parameters of a function can be estimated. Thus, the parameter vector p _Opt can be determined, the associated Transfer function approximately and / or best describes the measured transfer function. With the method selected here by way of example, this therefore corresponds to the parameter vector, in which the sum of the quadratic distances between the associated simulated total transfer function H _GS and the measured total transfer function H _GM becomes minimal. This can be as

being represented. This means that p _Opt corresponds to that parameter set from the parameter sets (combinations) p or p _D , whose accumulated squared deviation between the magnitude of the measured transfer function and the amount of the comparative transfer function to which the respective combination p is assigned has a minimum value. The summation shown can, for example, be obtained from the comparison device and obtained as a comparison result or part thereof of the selection device provided quality function. The selection means may perform an optimization thereof based on the obtained quality function, so that a result of the optimization represents the estimated parameters, or these can be obtained based on the determined result of the optimization (-sfunktion).

In simple terms, the comparison device can be designed to provide the comparison result based on a quality function. The selector may be configured to obtain the selection frequency based on an optimization function relating to the quality function. A result of the optimization, such as p _Opt, indicates an estimate of the electrical parameters.

As an alternative to the illustrated determination by means of the difference of the amounts, the vector p _{Opt can} also take place by means of a processing of the difference of the complex values, if there is phase information, this phase information should be as reliable as possible.

Alternatively, other non-differentiating algorithms may be used to estimate the electrical parameters, such as by optimization algorithms based on an interpolation, a downhill simplex algorithm or a bisection method (non-differentiating optimization methods). In order to speed up the estimation, in particular over calculation for all possible combinations (so-called brute force), the selection means may be arranged to determine or estimate the electrical parameters using a differentiating optimization method. For example. For this purpose, a Newton method, a modified Newton method, a gradient method, a logarithmic method or a conjugate gradient method can be implemented. An examination of the result can indicate whether the function to be minimized is strictly convex and, if necessary, measures can be derived therefrom. Measures to avoid a local minimum as a result can be realized by checking the minimum found, by suitably setting the starting point or several starting points and / or by manipulating the solution space.

With regard to an implemented optimization algorithm (method), a quality function can be selected and / or stored in a memory of the selection device and / or values thereof can be obtained by means of the comparison result. The quality function can be designed such that the optimization problem formulated in the context of the optimization algorithm is linearized, for example when an LQ (= linear-quadratic) method is used. These include, for example, an amount formation of the deviation of the real and imaginary part with respect to the transfer functions, comprising an addition in the quality function or a deviation of the complex amounts of the transfer functions. A motivation of these approaches is that usual optimization methods optimize functions with one-dimensional, real-valued value range. However, the transfer functions and thus the optimization problem can be complex. This may lead to a requirement that the optimization problem be transformed into a one-dimensional and real-valued optimization problem. Alternatively, various additional linearizing coordinate transformations, such as. As a logarithm or related to a computational effort to perform simple rational functions or trigonometric functions, eg. Cordic algorithms are used.

In summary, the parameter estimation can be performed by means of an optimization algorithm. The optimization algorithm may be applied to a possibly linearized, one-dimensional, and / or real-valued merit function to optimize it. This can be done, for example, according to a so-called L2 (Least Square or L ² ) standard with the aid of differentiating algorithms (Newton, Gradients etc.) or alternatively non-differentiating algorithms (Downhill Simplex, Interpolation, ...) be optimized. The optimizations refer, for example, to a minimization (such as a deviation or an error) or a maximization (such as a match).

The linearized quality function can be obtained, for example, from a non-linear quality function by means of a non-linear coordinate transformation. If the quality function is, for example, complex-valued, then a real-valued transfer function based on an amount formation of one or more possibly pre-transformed complex functions and / or by means of a subtraction, etc., can be obtained.

After estimating the parameter vector, the variable parameters L ', R' and M can also be assumed to be known. Thus, the energy transfer function H _E (f) and its global maximum, which in turn yields the optimal carrier frequency, can be calculated. In view of a fast and efficient implementation, a method can be used for this step, which minimizes this computational effort during operation, for example by a corresponding array in a memory of the selection device 36 or 36 ' is deposited, in which the previously determined relationships are deposited.

dargestellt werden. Die Auswahleinrichtung kann ausgebildet werden, um die Auswahlfrequenz basierend auf der Kombination geschätzter Parameter p_Opt, die als ein Ergebnis einer Optimierungsfunktion bezüglich einer Gütefunktion erhalten werden kann, zu bestimmen.By means of the model 40 can be similar to the overall transfer function 74 (H _G ) also an array with energy transfer functions 78 (H _E ) are calculated. In turn, the parameter vector p _{D can be} used for this purpose. The energy transfer function may be evaluated in advance for all identifiable vectors P _D and all adjustable and / or candidate carrier frequencies to determine the optimum (frequency). From the possible energy transfer functions known a priori in the application, a three-dimensional array A _f (p _D ) of size NL × NR × NM can be calculated, which directly contains the optimum carrier frequencies for all parameter combinations which can be estimated during operation. The array can be called

being represented. The selector may be configured to determine the selection frequency based on the combination of estimated parameters p _Opt , which may be obtained as a result of an optimization function related to a merit function.

With knowledge of the optimum carrier frequencies f _Opt , the transponder can be optimally supplied with energy at the corresponding frequency. If the communication is aborted, the procedure can be repeated if necessary, ie the transmission signal frequency can be set again. A combination p _D can be understood as synonymous with a combination p. The respective frequency f can be understood as one of the adjustable or to be considered transmit signal frequencies.

In a known application of the transponder system to which the same is interpretable, the reliability and speed of the method can be further improved by weighting and / or partially excluding certain parameter combinations in their (occurrence) probability. For example, in the case of a detuning of the resonant circuit by the environment, losses normally occur which can be weighted accordingly.

8th shows a schematic flow diagram of a method 100 for setting a read signal frequency of an RFID tag reading device, such as the RFID tag reading device 10 of the 20 , The procedure 100 includes a step 110 in which values of a transfer function describing a relationship between a first electrical signal and a second electrical signal of the RFID tag reading device are determined for a plurality of read signal frequencies.

In one step 120 For example, the values of the transfer function are compared with (respective) values of a plurality of comparison transfer functions to obtain a comparison result indicating a deviation between the detected values of the transfer function and the values of the comparative transfer functions.

In one step 130 selecting a selection function from the plurality of comparison transfer functions based on the comparison result, wherein the selection function has a minimum deviation from the comparison transfer function within a tolerance range.

In one step 140 a selection frequency is selected at which a partial transfer function assigned to the comparison transfer function has a maximum value (maximum of the functional value and / or the absolute value value) within a tolerance range.

In one step 150 the read signal frequency is adjusted based on the selection frequency.

In other words, the described concept or method can be carried out partially or completely blindly in the reading device for the local processes in the surrounding material, ie. H. no additional sensory acquisition or modeling of environmental conditions is required. Significant or even decisive is the recognition of the variable parameters.

9 shows a schematic flow diagram of a method 200 for providing comparative transfer functions of a transponder system with an RFID tag reader, such as the RFID tag reader 10 or 20 and possibly a nearby transponder. In one step 210 becomes a model, about the model 40 , the transponder system which is influenced by a plurality of electrical parameters of the transponder system. In one step 220 a combination of the electrical parameters is varied, such as a vector p, in which the parameters L ', R' and / or M are varied, wherein in each case a parameter L ', R' and M are combined into a combination. Alternatively or additionally, parameters of the transponder device can also be taken into account, as described in connection with FIG 5a is described. The varied parameters describe only a part of the system, ie good results can already be achieved if only a part of the system parameters is considered variable, such as those listed above.

In one step 230 the combination-influenced model of the transponder system is simulated for a plurality of transmission frequencies of the RFID tag reader to obtain simulated transmission function values for the plurality of transmission signal frequencies, wherein the transmission function values correlate a first electrical signal and a second electrical signal of the RFID Tag-reading device describe and wherein the transfer function values of different transmission signal frequencies can be combined into a transfer function or the transfer function are assigned.

In one step 240 the determined transfer function values and the combinations of parameters are stored in a memory.

In one step 250 is the varying of the electrical parameters (step 220 ), simulating (step 230 ) or the deposit (step 240 ) again until a plurality of transfer functions are stored in the memory.

In other words, the power supply of one or more transponders can be improved and / or stabilized with the method for carrier frequency adaptation. Depending on the environmental influence and the quality of the transponder and the reader oscillation circuit, the described concept can achieve high values regarding an induced voltage and / or a transmittable energy compared to known static or adaptive methods. The optimum carrier frequency corresponds for example to the frequency of the maximum of the energy transfer function, possibly within a tolerance range. Depending on the quality of the reader and / or the transponder antenna coil and the impedance of the transponder chip, this optimum carrier frequency deviates significantly from the resonant frequency of the impedance to which known methods would regulate, which leads to high or increased operating efficiencies compared to these methods , In particular, significant improvements to known adaptive systems can be achieved when the reader sweep circuit, including the source's equivalent internal resistance (amplifier), is of low to medium quality. Furthermore, the method presented here shows the more effect, the higher the quality of the transponder oscillating circuit or the higher the chip impedance of the transponder.

The quality of the transponder resonant circuit may have, for low to medium values, for example a value between Q = 5 and Q = 100, between Q = 7 and Q = 50 or between Q = 10 and Q = 30. At a high to very high quality of the reader coil (Q> 195) and a very low impedance chip impedance, such as a real part of 20 kΩ, a determined by means of the concept presented here carrier frequency compared to known adaptive method, a difference of 22.18, for example kHz (for example for a system in the low frequency range, which has an initial resonance frequency of about 125 kHz). This can lead to an improvement (increase) of the transponder-generated voltage U _T of up to 2.83 dB (approximately factor 1.39). With the same reader coil and increased chip impedance, for example, having a real part of 200 kΩ, the concept can provide an improvement of up to 7.3 dB (approx Factor of 2.31). Assuming an average Q = 44 for the reader coil, the increased chip impedance can provide an improvement of up to 9.24 dB (about a factor of 2.9) over a known adaptive system. These values are to be understood as exemplary values without limiting effect and merely represent an illustration of the advantageous effect of the increased energy transfer that can be achieved if, instead of regulating the supply signal frequency to the system eigenfrequency, a regulation takes place based on a maximum of an energy transfer function.

Although described embodiments describe a voltage source and a series resonant circuit on the reader and a parallel resonant circuit on the transponder, the reader may also have a series resonant circuit. Alternatively or additionally, a current source can also be arranged in order to excite the series or parallel resonant circuit on the reading device. Although the transponder is described in previous embodiments so that it has a parallel resonant circuit, alternatively or additionally, a series resonant circuit may be arranged. The reader as well as the transponder can furthermore have circuits for impedance and / or level adaptation.

Although according to the embodiments described above, a system optimization (adaptation of the read signal frequency) based on the transfer function with respect to the voltage at the reader to the voltage at the transponder chip is explained, this can be transmitted in the same or similar manner to the power at the transponder chip or a current in the transponder chip as output , In addition, depending on the type of source (voltage, current or power) on the reader, the appropriate size (current, voltage or power) can be used as input to the transfer function.

Embodiments described above can be used in RFID systems and sensor transponder systems, in particular with passive transponders and in particular in systems with readers in a varying environment, varying coupling (inductive or capacitive) to the transponder and / or metal-sheathed transponders. These include, for example, sensor transponders in metal screws for harsh environments, titanium-encapsulated medical implants or transponders used in wireless pressure sensors in a vacuum insulation panel (VIP).

Embodiments may also be employed in wireless power transfer systems, particularly transmitters in a varying environment, and receiver devices having conductive materials. The conductive materials may for example form a shell (metallic sheath) of the receiver side and / or mean a capacitive coupling. In addition, scenarios are conceivable in which a coupling (inductive or capacitive) to the transmitter varies.

RFID-based radio-frequency identification systems influenced by an environment are present, for example, in the area of so-called flight cases, in which, for the most part, several transponders are to be detected between metallic loads.

Previously described embodiments thus enable a solution while maintaining the framework conditions that the solution can also be used for mobile systems, that they can be implemented in handy dimensions and can be designed energy-efficient and flexible. This can be achieved with little hardware effort. The carrier frequency is digitally adjustable, for example. The solutions presented, for example, provide a method for the case when the reader resonant circuit is detuned, such as based on a changing environment.

The antenna resonant circuits of an inductively coupled transponder system form a system of coupled oscillators. Channels for energy and data transmission can have various transfer functions ( 78 and 82 ) exhibit. In a conductive environment, transponder systems in the so-called low-frequency range (LF) are preferably used. However, conductive materials also significantly affect LF systems. The resonance frequency of the resonant circuits is detuned and eddy currents in the surrounding material lead to losses. Ferromagnetic materials also change the transfer functions. Furthermore, with very high magnetic coupling of the coils in the resonant circuits, significantly changing characteristics in the transfer functions occur.

In described exemplary embodiments, the reading device has a series resonant circuit and the transponder has a parallel resonant circuit. The carrier signal can be generated in the reader by means of a simple digitally generated square wave signal or a variable frequency sine wave signal. Legal regulations can be easily adhered to if necessary by setting limit values for the signal frequencies be set. Even with the use of a rectangular signal as a carrier signal is an almost sinusoidal signal at sufficient quality of the resonant circuit on the reactances.

An inductively coupled transponder system can be represented by means of a transformer equivalent circuit diagram, which is supplemented by the respective capacities and resistances. For this a model ( 4 ) are derived with transfer functions.

Although reference is made in the above-described embodiments to RFID tag readers or to transponder systems, wireless power transmission systems (WPTs) may be implemented in the same or similar manner with the apparatus and methods described above.

Although some aspects have been described in the context of a device, it will be understood that these aspects also constitute a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device.

Depending on particular implementation requirements, embodiments of the invention may be implemented in hardware or in software. The implementation may be performed using a digital storage medium, such as a floppy disk, a DVD, a Blu-ray Disc, a CD, a ROM, a PROM, an EPROM, an EEPROM or FLASH memory, a hard disk, or other magnetic disk or optical memory are stored on the electronically readable control signals that can cooperate with a programmable computer system or cooperate such that the respective method is performed. Therefore, the digital storage medium can be computer readable. Thus, some embodiments according to the invention include a data carrier having electronically readable control signals capable of interacting with a programmable computer system such that one of the methods described herein is performed.

In general, embodiments of the present invention may be implemented as a computer program product having a program code, wherein the program code is operable to perform one of the methods when the computer program product runs on a computer. The program code can also be stored, for example, on a machine-readable carrier.

Other embodiments include the computer program for performing any of the methods described herein, wherein the computer program is stored on a machine-readable medium.

In other words, an embodiment of the method according to the invention is thus a computer program which has a program code for performing one of the methods described herein when the computer program runs on a computer. A further embodiment of the inventive method is thus a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program is recorded for carrying out one of the methods described herein.

A further embodiment of the method according to the invention is thus a data stream or a sequence of signals, which represent the computer program for performing one of the methods described herein. The data stream or the sequence of signals may be configured, for example, to be transferred via a data communication connection, for example via the Internet.

Another embodiment includes a processing device, such as a computer or a programmable logic device, that is configured or adapted to perform one of the methods described herein.

Another embodiment includes a computer on which the computer program is installed to perform one of the methods described herein.

In some embodiments, a programmable logic device (eg, a field programmable gate array, an FPGA) may be used to perform some or all of the functionality of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor to perform one of the methods described herein. In general, in some embodiments, the methods are performed by any hardware device. This may be a universal hardware such as a computer processor (CPU) or hardware specific to the process, such as an ASIC.

The embodiments described above are merely illustrative of the principles of the present invention. It will be understood that modifications and variations of the arrangements and details described herein will be apparent to others of ordinary skill in the art. Therefore, it is intended that the invention be limited only by the scope of the appended claims and not by the specific details presented in the description and explanation of the embodiments herein.

Claims (26)

Contraption ( 10 ; 20 ) for inductive or capacitive transmission of a supply signal ( 22 ) having a supply signal frequency (f), comprising: a determination device ( 26 ), which is designed to have a transfer function (H _M ), which determines a relationship between a first electrical signal ( 16 ) and a second electrical signal ( 24 ) of the device ( 10 ; 20 ), for a plurality of supply signal _frequencies (f _NF ) to determine; a comparator ( 32 ; 32 ' ) which is _adapted to compare the transfer function (H _M ) with a plurality of comparison transfer functions (H _Sx ) and to obtain a comparison result ( 34 ; 34 ' ), which indicates a deviation between the determined transfer function (H _M ) and the comparison transfer functions (H _Sx ); a selection device ( 36 ; 36 ' ), which is designed to be based on the comparison result ( 34 ; 34 ' ) select a selection function (H _S ) from the plurality of comparison transfer functions (H _Sx ), wherein the selection function (H _S ) has a minimum deviation from the transfer function (H _M ) within a tolerance range, and wherein the selection means (H) 36 ; 36 ' ) is further _configured to select a selection frequency (f _Opt ) at which a function (H _E ) associated with the selection function has a maximum value (| H _E | _max ) within a tolerance range; and an adjustment device ( 38 ) configured to adjust the supply signal frequency (f) based on the selection frequency (f _Opt ). Device according to claim 1, which is an RFID tag reading device and in which the supply signal ( 22 ) to a transponder device ( 48 ) is inductive or capacitive transferable read signal or in which the device is a power source of a wireless power supply system and is adapted to emit the power supply signal for the supply of inductively or capacitively coupled consumers. Apparatus according to claim 1 or 2, wherein the transfer function (H _M ) is a ratio between an output (U _rec , U ' _Rec ) and an input (U _R ) of the device ( 10 ; 20 ), in which the first electrical signal ( 16 ) of the input variable (U _R , I _L ) is assigned and in which the second electrical signal ( 24 ) is assigned to the output variable (U _rec , U ' _Rec ). Device according to Claim 3, in which the first electrical signal ( 16 ) an electrical supply signal (U _R , I _L ) of a transmitting device ( 12 ) of the device ( 10 ; 20 ) and at which the second electrical signal ( 24 ) is associated with an electrical reception signal (U ' _Rec ) obtainable by a receiving device of the device and influenced by an environment of the device. Device according to Claim 4, in which the electrical supply signal (U _R , I _L ) is one of a voltage signal (U _R ) which is applied to an amplifier output of the transmitting device (U _R , I _L ). 12 ), a current signal (I _L ) correlated with the voltage signal, a power signal correlated with the voltage signal, and the received signal (U ' _Rec ) of a voltage at a capacitor influenced by the environment of the device ( 68b ), which with a transmitting coil ( 58 ) of the transmitting device ( 12 ) forms a resonant circuit, a hereby correlated current signal, a coil voltage (U _L ), which at the transmitting coil ( 58 ) drops, a voltage (U _RI ), which is connected to a resistor ( 62 ) of the transmitting device ( 12 ) falls, a capacitively detected coil voltage and an inductively detected coil voltage of the transmitting coil ( 58 ). Device according to Claim 5, in which the transmitting coil ( 58 ) of the transmitting device ( 12 ) the resonant circuit with a capacitive voltage divider circuit ( 64 ), wherein the capacitive voltage divider circuit ( 64 ) is adapted to the second electrical signal ( 24 ). Apparatus according to claim 5 or 6, wherein the current signal (I _L ) correlated with the voltage signal is a total current of the resonant circuit. Device according to one of the preceding claims, in which the comparison transfer functions (H _Sx ) of a plurality of variable electrical parameters (L ', R', M) of the device ( 20 ) in which each of the comparison transfer functions (H _Sx ) is a combination (p) of parameter values (L ' _{1, ..., NL} , R' _{1, ..., NR} , M ' _{1, ..., NM} ) of the electrical parameters (L ', R', M) is assigned and in which the selection device ( 36 ) is adapted to select the selection frequency (f _opt ) based on the combination (p _opt ) of parameters associated with the selection function (H _s ). Apparatus according to claim 8, which is adapted to receive the supply signal ( 22 ) and in which the electrical parameters (L ', R', M) have an electrical equivalent resistance (R ') of the device ( 20 ) and a replacement inductance (L '). Device according to claim 9, wherein the electrical parameters (L ', R', M) further include a mutual inductance (M) coming from an environment of the device ( 20 ) on the device ( 20 ) includes. Device according to claim 9 or 10, wherein the electrical parameters (L ', R', M) further comprise an inductance and a resistance of a coil ( 52 ) of a device inductively coupled to the device ( 48 ). Apparatus according to claim 8, which is adapted to receive the supply signal ( 22 ) capacitively and in which the electrical parameters (L ', R', M) have an electrical equivalent resistance (R ') of the device ( 20 ) and a replacement capacity of the device ( 20 ). Apparatus according to claim 12, wherein the electrical parameters (L ', R', M) further include a counter capacitance derived from an environment of the apparatus ( 20 ) on the device ( 20 ) includes. Apparatus according to claim 12 or 13, wherein the electrical parameters (L ', R', M) further comprise a capacitance of a capacitor and an equivalent resistance of the capacitor of a device capacitively coupled to the device ( 48 ). Apparatus according to any one of claims 8-14, wherein said selecting means is _adapted to estimate the combination (p _Opt ) of electrical parameters (L ', R', M) based on the comparison result and to determine the estimated values based on the estimated parameters Selection frequency to determine. Device according to Claim 15, in which the selection device ( 36 ' ) is configured to estimate the combination (p _opt ) electrical parameters (L ', R', M) based on an optimization method. Device according to Claim 16, in which the selection device ( 36 ' ) is adapted to estimate the parameters (L ', R', M) based on a differentiating optimization method. Device according to one of claims 8-17, in which the comparison device ( 32 ; 32 ' ) is adapted to the comparison result ( 34 ; 34 ' ) based on a quality function and in which the selection device ( 36 ; 36 ' ) is adapted to obtain the selection frequency (f _Opt ) based on a quality function optimization function, wherein a result of the optimization indicates an estimate of the electrical parameters (L ', R', M). Device according to one of claims 8-18, in which the selection device ( 36 ' ) a memory ( 46 ), in which information (A _f ) is stored, which specifies a selection frequency (f) to be selected for each of a plurality of parameter combinations (p). Device according to Claim 19, in which a partial transfer function (H _E ) of a system ( 40 ) that the device ( 10 ; 20 ) and a coupled receiver device ( 48 ), in which the selection frequency (f _opt ) is within a tolerance range ( 86 ) has a maximum function, wherein the partial transfer function (H _E ) is an energy transfer from the device ( 10 ; 20 ) to the receiver device ( 48 ) describes. Device according to one of Claims 8-20, in which the electrical parameters (L ', R', M) are a mutual inductance which is determined by an inductance of a transmitting coil ( 58 ) of the transmitting device ( 12 ) on a spool ( 58 ) a receiver device ( 48 ) and a mutual inductance acting on the coil ( 58 ) of the recipient device ( 48 ) on the transmitting coil ( 52 ) includes. Device according to one of the claims 8-21, in which a probability value is assigned to the combinations (p) of parameters (L ', R', M) and in which the selection device ( 36 ' ) is adapted to estimate the parameters (L ', R', M) based on the probability value. Device according to one of the preceding claims, in which the determining device ( 26 Is formed) to (to vary f _NF) sequentially in order (for each supply signal frequency f _LF) has a value (H _x (nF), the supply signal frequency) of the transfer function (H _Sx) to be determined and in order based (on the determined values H _Sx to obtain (nF)) of the transfer function (H _Sx), the transfer function (H _Sx). Method for setting a supply signal frequency of a device for inductive or capacitive transmission of the supply signal, comprising the following steps: determining ( 110 ) of a transfer function (H _M ), which determines a relationship between a first electrical signal ( 16 ) and a second electrical signal ( 24 ) of the device ( 10 ; 20 ) for a plurality of supply signal _frequencies (f _NF ); To compare ( 120 ) values of the transfer function (H _M ) with values of a plurality of comparison transfer functions (H _Sx ) to obtain a comparison result ( 34 ; 34 ' ), which indicates a deviation between the values of the determined transfer function (H _M ) and the values of the comparative transfer functions (H _Sx ); Choose ( 130 ) a selection function (H _S ) from the plurality of comparison transfer functions (H _Sx ) based on the comparison result ( 34 ; 34 ' ), wherein the selection function (H _S ) within a tolerance range has a minimum deviation from the transfer function; Choose ( 140 ) a selection frequency (f _Opt ) at which a part transfer function (H _E ) assigned to the selection function (H _S ) has a maximum value (| H _E | _max ) within a tolerance range; and setting ( 150 ) of the supply signal frequency (f) based on the selection frequency (f _Opt ). A method according to claim 24, further _{comprising the} step of: providing the comparison transfer functions (H _Sx ) of a transmission system ( 40 ), further comprising the following substeps: 210 ) of a model of the system ( 40 ) of a plurality of electrical parameters (L ', R', M) of the device ( 10 ; 20 ) for inductive or capacitive transmission of a supply signal ( 22 ) is influenced; Vary ( 220 ) a combination (p) of the electrical parameters (L ', R', M); Simulate ( 230 ) of the model influenced by the combination (p) for a plurality of the supply signal _frequencies (f _NF ) of the device ( 10 ; 20 ) to obtain simulated transfer function _values (H _Sx (NF)) for the plurality of supply _{signal frequencies} (f _NF ), wherein the transfer function values (H _Sx (NF)) correlate a first electrical signal (H 16 ) and a second electrical signal ( 24 ) of the device ( 10 ; 20 ) and wherein the transfer function _values (H _Sx (NF)) of different supply _{signal frequencies} (f _NF ) are assignable to a transfer function (H _Sx ); Deposit ( 240 ) of the determined transfer function values (H _Sx (NF)) and the combination (p) of parameters in a memory ( 44 ; 46 ); Re-varying the electrical parameters, simulating or storing ( 240 ) until a plurality of transfer functions (H _Sx ) in the memory ( 44 ; 46 ) is deposited. A computer program comprising program code for carrying out the method of claim 24 or 25 when the program is run on a computer.

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