Radio transponder and method for data transmission between a radio transponder reader and the radio transponder

Abstract

A radio transponder and method for data transfer between a radio transponder reading device and the radio transponder, wherein a control unit of the radio transponder controls a change in a load impedance via a control signal having a selected switching pulse frequency and a selected switching pulse quantity to produce a response signal, where the control unit codes multiple-valued at least ternary symbols into the control signal, and where symbol values are assigned to respective switching pulse sequences each having a unique combination of switching pulse frequency, switching pulse number and phase shift such that only combinations for which the quotient of switching pulse number and switching pulse frequency lies within a predefined value range are selected.

Claims

1. A method for data transmission between a radio transponder reader and a radio transponder, the method comprising: modulating, by the radio transponder reader, at least one control command onto a radio carrier signal and transmitting the modulated radio carrier signal to the radio transponder; receiving, by the radio transponder, the modulated radio carrier signal via an inductive antenna arrangement, a load modulation unit comprising a variable load impedance being connected to the inductive antenna arrangement; generating, by a control unit of the radio transponder, a response signal by controlling a change of the load impedance via a control signal having a selected switching pulse frequency and a selected number of switching pulses; coding, by the control unit, multi-value, at least ternary, symbols into the control signal; and assigning respective symbol values to switching pulse sequences each having a unique combination of switching pulse frequency, number of switching pulses and phase shift; wherein only combinations whose quotient of number of switching pulses and switching pulse frequency is within a stipulated range of values are selected.

2. The method as claimed in claim 1, wherein the symbols are coded utilizing at least a first and a second switching pulse frequency, a first and a second number of switching pulses and a first and a second phase shift.

3. The method as claimed in claim 2, wherein the symbols are coded utilizing at least a first and a second switching pulse frequency and a first and a second number of switching pulses; and wherein a quotient of first number of switching pulses and first switching pulse frequency and a quotient of second number of switching pulses and second switching pulse frequency differ from one another by no more than 10%.

4. The method as claimed in claim 2, wherein precisely one symbol value is additionally utilized, said precisely one symbol value including an assigned tiny switching pulse sequence which deactivates a load modulation for a stipulated period.

5. The method as claimed in claim 4, wherein the stipulated period is within the stipulated range of values of the quotient of number of switching pulses and switching pulse frequency.

6. The method as claimed in claim 1, wherein the symbols are coded utilizing at least a first and a second switching pulse frequency and a first and a second number of switching pulses; and wherein a quotient of first number of switching pulses and first switching pulse frequency and a quotient of second number of switching pulses and second switching pulse frequency differ from one another by no more than 10%.

7. The method as claimed in claim 6, wherein precisely one symbol value is additionally utilized, said precisely one symbol value including an assigned tiny switching pulse sequence which deactivates a load modulation for a stipulated period.

8. The method as claimed in claim 7, wherein the stipulated period is within the stipulated range of values of the quotient of number of switching pulses and switching pulse frequency.

9. The method as claimed in claim 1, wherein precisely one symbol value is additionally utilized, said precisely one symbol value including an assigned tiny switching pulse sequence which deactivates a load modulation for a stipulated period.

10. The method as claimed in claim 9, wherein the stipulated period is within the stipulated range of values of the quotient of number of switching pulses and switching pulse frequency.

11. The method as claimed in claim 1, wherein the control signal comprises essentially square-wave pulses or temporarily has no signal strength.

12. The method as claimed in claim 11, wherein the square-wave pulses each have a pulse duration which corresponds to half of one period duration.

13. The method as claimed in claim 1, wherein the control unit assigns the symbol values to switching pulse sequences in accordance with a code table stored in a memory unit of the radio transponder; and wherein the radio transponder reader stores a corresponding code table.

14. The method as claimed in claim 1, wherein the control unit utilizes the switching pulse sequences assigned to the symbol values to control a load modulation via combined frequency shift keying, phase shift keying and modulation deactivation.

15. The method as claimed in claim 1, wherein selected symbol values represent control commands for data flow control between radio transponder reader and radio transponder, for at least one of (i) collision detection during simultaneous transmission attempts by multiple radio transponders and (ii) identification of a start or end of a data frame.

16. The method as claimed in claim 1, wherein the radio transponder reader codes the control command and subsequently modulates said control command onto the radio carrier signal.

17. A radio transponder, comprising: an inductive antenna arrangement configured to receive a modulated radio carrier signal transmitted by a radio transponder reader, said modulated radio carrier signal comprising at least one control command modulated onto the radio carrier signal; a load modulation unit connected to the antenna arrangement and comprising a variable load impedance; a control unit configured to: generate a response signal by controlling a change of the load impedance via a control signal which has a selected switching pulse frequency and a selected number of switching pulses, and code multi-value, at least ternary, symbols into the control signal; wherein the radio transponder is configured to assign respective symbol values to switching pulse sequences each having a unique combination of switching pulse frequency, number of switching pulses and phase shift; and wherein only combinations whose quotient of number of switching pulses and switching pulse frequency is within a stipulated range of values are selectable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is outlined in more detail below using an exemplary embodiment with reference to the drawing, in which:

(2) FIG. 1 shows a schematic depiction of a radio transponder system having a radio transponder and a radio transponder reader connected thereto in accordance with the invention;

(3) FIG. 2 shows a first switching pulse sequence for load modulation for the radio transponder shown in FIG. 1 in accordance with the invention;

(4) FIG. 3 shows further switching pulse sequences and associated symbol values in accordance with the invention; and

(5) FIG. 4 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(6) The radio transponder system schematically depicted in FIG. 1 comprises a radio transponder reader/writer 200 and a radio transponder 100 inductively couplable thereto. Accordingly, the radio transponder 100 and the radio transponder reader/writer 200 each have an inductive antenna arrangement 101, 201. The antenna arrangements 101, 201 are therefore depicted as inductances coupled to one another in FIG. 1. The radio transponder reader/writer 200 in the present exemplary embodiment additionally comprises a data input 202 for receiving control commands to be transmitted to the radio transponder 100, a modulation unit 203, a demodulation unit 204 and a data output 205 for providing information read from the radio transponder 100. In the present exemplary embodiment, the radio transponder 100 is an RFID tag. Accordingly, the radio transponder reader/writer 200 is an RFID reader/writer.

(7) The radio transponder 100 comprises a load modulation unit formed by a load impedance 102 and by a control unit 104 for the load impedance 102. Additionally, the radio transponder 100 has a memory unit 105 that can be read or written to via the radio transponder reader/writer 200. The memory unit 105 stores at least one identifier assigned to the radio transponder 100, which identifier is not usually changed. The control unit 105 and the memory unit 105 in the present exemplary embodiment are integrated in a circuit 110 that comprises both units.

(8) The radio transponder 100 additionally comprises a capacitor arrangement 103 arranged in parallel with the antenna arrangement 101 and the load impedance 102. The capacitor arrangement 103 is preferably variable with respect to its capacitance and in particular forms a tunable resonant circuit with the antenna arrangement 101. To adjust its capacitance, the capacitor arrangement 103 can have, for example, a plurality of capacitors arranged in parallel with one another that are each arranged in series with a fuse and can be disconnected via the respective fuse to tune the resonant circuit. In the present exemplary embodiment, the radio transponder 100 is operated passively, i.e., the transponder 100 has no power supply of its own, but rather is supplied with power via an electromagnetic alternating field generated by the radio transponder reader/writer 200.

(9) For the purpose of data transmission between the radio transponder reader/writer 200 and the radio transponder 100, the radio transponder reader/writer 200 uses its antenna arrangement 100 to generate an electromagnetic alternating field that comprises at least one carrier frequency selected on the radio transponder reader/writer 200. In particular, the radio transponder reader/writer 200 modulates at least one coded control command onto a radio carrier signal at the selected carrier frequency and transmits the modulated radio carrier signal 1 to the radio transponder 100.

(10) The radio transponder 100 receives the modulated radio carrier signal 1 via its inductive antenna arrangement 101 and uses its control unit 104 to decode the control command transmitted by the radio transponder reader/writer 200. To generate a response signal 2, the control unit 104 of the radio transponder 100 controls a change of the load impedance 102 via a control signal 141. In this manner, the radio transponder 100 codes and modulates its response into the electromagnetic alternating field generated by the radio transponder reader/writer 200, specifically by changing the field via load modulation.

(11) The variable load impedance may, in the simplest case, be provided by a switchable load resistor, for example. Here, the control unit 104 of the radio transponder 100 generates the response signal 2 by controlling connection of the load resistor via the control signal 141. When the load resistor is connected, the radio transponder 100 consumes an energy component of the electromagnetic alternating field generated by the radio transponder reader/writer 200. This is detected by the radio transponder reader/writer 200 via its demodulation unit 204. In this manner, the radio transponder reader/writer 200 can provide information read from the memory unit 105 of the radio transponder 100, for example, at its data output 204.

(12) FIG. 2 depicts a first switching pulse sequence 11 for the control signal 141 by way of illustration, where the control signal has a selected switching pulse frequency f.sub.1 and a selected number of switching pulses n.sub.1 (in this case: 4). This results in a symbol duration T.sub.1=n.sub.1/f.sub.1 for the first switching pulse sequence that is the reciprocal of a possible data rate. An actual data rate is normally lower than this possible data rate if additional coding rules, for example, Manchester coding or pulse position coding, are also taken into consideration. These additional coding rules firstly provide opportunities for detecting transmission errors. The additional coding rules can secondly allow further functionalities, such as collision detection or insertion of additional redundancy for increased data transmission security.

(13) Based on the first switching pulse sequence 11 shown in FIG. 2 and further switching pulse sequences 10, 12, 13 depicted in FIG. 3, the control unit 104 codes symbols that each represent one of multiple values into the control signal 141. In any event, the coded symbols are at least ternary, i.e., the coded symbols have 3 values. In the present exemplary embodiment, quaternary symbols are used, which can assume U, V, W or X as symbol values and therefore have an information content of 2 bits. The control unit 104 assigns the symbol values U-X to the switching pulse sequences 10, 11, 12, 13 in accordance with a code table stored in the memory unit 105 of the radio transponder 100. A corresponding code table is also stored in the radio transponder reader/writer 200. The first switching pulse sequence 11 has the symbol value V assigned to it in the code table, for example, while a second switching pulse sequence 12 is assigned the symbol value W, a third switching pulse sequence 13 is assigned the symbol value X and a fourth switching pulse sequence 10 is assigned the symbol value U.

(14) In the present exemplary embodiment, the first to third switching pulse sequences 11, 12, 13 each have a unique combination of switching pulse frequency f.sub.1, f.sub.2, f.sub.3=f.sub.1, number of switching pulses n.sub.1=4, n.sub.2=5, n.sub.3=4 and phase shift φ.sub.1=0°, φ.sub.2=0°, φ.sub.3=180°. Only combinations whose quotient of number of switching pulses n.sub.i and switching pulse frequency f.sub.i is within a stipulated range of values D.sub.min−D.sub.max are admissible. The symbols are preferably coded using at least a first (f.sub.1=f.sub.3) and a second (f.sub.2) switching pulse frequency and also a first (n.sub.1=n.sub.3) and a second (n.sub.2) number of switching pulses, the quotients n.sub.1/f.sub.1=n.sub.3/f.sub.3, n.sub.2/f.sub.2 of which differ from one another by no more than 10%. In this manner, the possible data rate remains sufficiently constant in each case.

(15) The fourth switching pulse sequence 10 assigned to the symbol value U is a tiny switching pulse sequence that comprises no switching pulses. This tiny switching pulse sequence deactivates a load modulation for a stipulated period that is within the stipulated range of values D.sub.min−D.sub.max of the quotient of number of switching pulses n.sub.i and switching pulse frequency f.sub.i. The control signal 141 thus either comprises essentially square-wave pulses or temporarily has no signal strength. In the present exemplary embodiment, the square-wave pulses each have a pulse duration that corresponds to half of one period duration (duty factor 50%). All in all, the control unit uses the switching pulse sequences 10, 11, 12, 13 assigned to the symbol values U-X to control a load modulation using combined frequency shift keying, phase shift keying and modulation deactivation.

(16) It is fundamentally possible for selected symbols to represent control commands for data flow control between the radio transponder reader/writer 200 and the radio transponder 100, for collision detection during simultaneous transmission attempts by multiple radio transponders and/or for identification of a start or end of a data frame.

(17) FIG. 4 is a flowchart of the method for data transmission between a radio transponder reader 100 and a radio transponder 200.

(18) The method comprises modulating, by the radio transponder reader 200, at least one control command onto a radio carrier signal and transmitting the modulated radio carrier signal 1 to the radio transponder 100, as indicated in step 410.

(19) Next, the radio transponder 100 receives the modulated radio carrier signal 1 via an inductive antenna arrangement 101, as indicated in step 420. In accordance with the invention, a load modulation unit comprising a variable load impedance 102 is connected to the inductive antenna arrangement 101.

(20) Next, a control unit 104 of the radio transponder 100 generates a response signal 2 by controlling a change of the load impedance 102 via a control signal 141 having a selected switching pulse frequency and a selected number of switching pulses, as indicated in step 430.

(21) Next, the control unit 104 codes multi-value, at least ternary, symbols into the control signal 141, as indicated in step 440.

(22) Next, respective symbol values U-X are assigned to switching pulse sequences 10, 11, 12, 13 each having a unique combination of switching pulse frequency, number of switching pulses and phase shift, as indicated in step 450. In accordance with the invention, only combinations whose quotient of number of switching pulses and switching pulse frequency is within a stipulated range of values are thus selected.

(23) Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.