SE531799C2 - A device for wireless operation and a method for operating the device - Google Patents

Description

25 30 '' 799 "sleep" mode and which can be activated at any time by a predetermined signal. Furthermore, there is a need for a device with an identity and possibly data that can be detected by a remote system.

SUMMARY OF THE INVENTION Accordingly, the present invention preferably seeks to alleviate, mitigate or eliminate one or more of the above-identified shortcomings in the art and the disadvantages individually or in any combination.

According to one aspect of the invention, there is provided a method of operating a device comprising a receiver, comprising: receiving a first signal with a first frequency from the receiver: and retransmitting a second signal with a second frequency after a latency time and for a period of time depending on receiving a signal with said first frequency and with a signal strength above a threshold value. The second frequency may be the same as said first frequency or may differ from said first frequency by a difference frequency.

According to one embodiment, the method comprises: receiving transmitted signals with an antenna; passing said signals received by the antenna to a resonant circuit tuned to a second frequency near said first frequency; triggering a regenerative circuit through said signals if said signal strength after the resonant circuit is above said threshold value; operating said regenerative circuit to transmit a signal at said second frequency; and attenuating said regenerative circuit after said time period so that the signal with the second frequency ceases. The method may further comprise: operating said regenerative circuit before triggering in a position power mode with a low energy consumption; and, after triggering, bringing said regenerative circuit into self-oscillation with a signal strength of a predetermined value and having said second sequence: and attenuating said self-oscillation after said time period, thereby bringing the regenerative circuit back to said low power position.

According to another embodiment, the device comprises a transmitter device and a receiver device in mutual wireless communication, the method further comprising: transmitting said signal at said first frequency through the transmitter device during a transmission time period, and listening with said transmitter device for said retransmission period after said transmission period; transmitting additional signals with new frequencies selected according to a special schedule, and listening with said transmitter transmission for retransmissions after said transmission time periods; and controlling the receiving device to retransmit only if said signals are received in a specific sequence order predetermined in the receiving device.

According to a further embodiment, the method comprises: providing said receiver with an input signal; adjusting said second frequency to a value in depending on said input signal; whereby said receiver transmits at said second frequency depending on said input signal. The new frequencies, which are selected for the additional signals, may be selected depending on the retransmissions. The returned signal can activate a control circuit to control further operation of the device.

The device can be used in an article overflow system comprising a reader and a plurality of identity markings.

According to another aspect of the invention, there is provided a device for wireless operation, comprising: an antenna for receiving transmitted signals; a resonant circuit tuned to a first frequency to select a signal having a first frequency from the signals received by the antenna; a trigger circuit received the selected signal; an oscillation circuit operated by said trigger circuit to start oscillating at a second frequency upon triggering in response to receiving a signal of said first frequency and a signal strength above a threshold value; and attenuating the circuit began to stop said oscillations after a period of time. The first frequency may be equal to said second frequency or different from said second frequency by a difference frequency.

The device may further comprise: a control circuit for operating the oscillation circuit depending on the reception of signals in a particular sequence of sequences predetermined in the device. The control circuit may be arranged to receive an input signal and adjust said second frequency depending on said input signal.

The device may have oscillation circuits with different oscillating frequencies, and said control circuit may select an oscillation circuit depending on said input signal.

The device can be used in an article monitoring system comprising a reader and several identity markings.

DETAILED DESCRIPTION OF THE DRAWINGS Additional objects, features and advantages of the invention will become apparent from the following detailed description of embodiments of the invention, taken in conjunction with the accompanying drawings, in which: Fig. 1. is a schematic diagram of an RFID system in which the invention can be used.

Pig. 2 is a schematic diagram of a prior art identity tag used in the RFID system of FIG. 1.

Pig. 3 is a schematic diagram of an embodiment of a device according to the invention.

Pig. 4 is a more detailed schematic diagram of the device according to Figs. 3.

Pig. 5 is a detailed schematic diagram of a device according to another embodiment.

Pig. 6 is a detailed schematic diagram of a circuit according to a further embodiment.

Pig. 7 is a diagram of an amplifier curve of a non-linear amplifier in the embodiments of FIG. 6.

Pig. 8 is a diagram of the bandpass property of a bandpass alteration embodiment according to FIG. 6.

Pig. 9 is a schematic diagram of a device according to a further embodiment.

Pig. 10 is a diagram of frequency selection.

Pig. ll is a diagram similar to Pig. 10 of another frequency selection scheme.

Pig. 12 is a diagram of a bandpass filter of the device according to any of the above embodiments.

Pig. 13 is a schematic diagram of a device including a "wake-up" feature.

Pig. 14 is a schematic diagram of a device comprising a number of regenerative circuits.

Pig. 15 is a detailed schematic diagram similar to FIG. 6 of another embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS The embodiments described below describe the best mode and enable one skilled in the art to practice the invention. The different properties of the embodiments can be combined in other ways than those described below. The invention can be made in many different forms and should not be construed as limiting the embodiments set forth herein.

Rather, these embodiments are provided so that this description will be detailed and complete and will fully express the scope of the invention to those skilled in the art. The invention is limited only by the appended claims.

Pig. 1 is a schematic view showing an RFID system 10 comprising a reader 11 and a number of labels 12, 13, 14, 15, 16. Although five labels are shown, such systems may include a large number of labels, some of which are within the scope of a particular reader. 1 1.

The reader 11 comprises a combined receiver and transmitter (transmitter / receiver) which transmits a radio signal with predetermined frequencies and listens for response signals from the markings 12, 13, 14, 15, 16.

The markings 12, 13, 14, 15, 16 can be different configurations depending on the system.

The marking 12, 13, 14, 15, 16 may be a passive device absorbing energy, for example at said predetermined frequencies. The reader 11 can sense the absorbance and determine a property of the marking 12, 13, 14, 15, 16. The passive device does not need a power supply unit.

A more versatile, active label includes a receiver and a transmitter.

The receiver is a low power receiver which (intermittently) listens for radio signals transmitted by the reader. When the receiver senses a radio signal, for example in a predetermined frequency range, the marking is activated and a power supply source is connected to the transmitter to transmit a response. The answer may be a confirmation signal and / or may include certain information, such as the identity of the label and / or additional data.

The internal power supply can be expanded with energy obtained from the radio signal transmitted by the reader. Such a label needs an internal power supply source, but energy consumption can be very low in stand-by mode. However, the receiver must be activated at regular or controlled intervals even if there is no reader within reach, thereby consuming energy.

The label can have an identity and can respond to the reader only if the identity matches a signal sent by the reader. Such an identity may be a series of frequencies transmitted by the reader. The reader may be arranged to transmit signals at different frequencies in different frequency bands, for example frequencies f0. to f79 included in a free band in the 2.4 GHz range that is open to low power devices. Such a frequency band may include 80 bands with a frequency range of 1 MHz, cf. B1uetooth® standards.

The reader can, for example, send the frequency series f1, f5, f33, f2 and the marking with the identity vector (1, S, 33, 2) will be activated and send a response. 10 15 20 25 30 35 531 799 The label is produced in large quantities and should be as cheap as possible.

Thus, there is a requirement for a design that is as simple as possible. Furthermore, energy consumption should be minimized so that small batteries can be used. The battery should last for the entire life cycle of the product, which may be five years or more.

The receiver in the tag may be constructed as a heterodyne receiver, as shown in Fig. 2. The tag 20 includes an antenna 21 connected to a broadband amplifier 22 with an output connected to a mixer 23. The signal from the antenna is mixed with a signal of a predetermined frequency. from an oscillator 24, such as a VCO, a voltage controlled oscillator. The difference signal from the mixer 23 is fed to a narrowband, intermediate frequency IF amplifier 25 and the amplified signal is delivered to an output terminal, which is connected to some evaluation circuit, not shown. Thus, the frequency of VCO 24 determines which antenna signal frequency is amplified by the IF amplifier 25. However, the energy consumption of such a receiver is relatively large. Activation of the receiver only for short periods of time at long intervals reduces the energy consumption of the label 20.

Fig. 3 shows an embodiment of an active label comprising a non-linear reinforced part. The marking 30 comprises an antenna 31 connected to a bandpass filter 32, which may be an inductor connected in series with a capacitance. An amplifier 33 is connected across the bandpass filter. The amplifier 33 may be a threshold amplifier, in which the signal must be above a particular threshold value in order to be amplified. When the signal from the antenna 31 is above said threshold value, after filtering through filter 32, the signal is amplified by amplifier 33 and fed back to the input of filter 32 as an even larger signal. Since the amplifier 33 is connected with positive feedback, the amplifier 33 will enter the self-oscillation g within a short period of time, called the latency period. The oscillations produce a signal transmitted by the antenna 31. The reader ll can sense this transmitted signal as a response. The signal produced by the amplifier 33 is emitted at an output to a control circuit of the mark 30. At the same time, the output signal controls a switch 34 in the feedback loop of the amplifier 33 via a control line 35. When the oscillation signal is large enough, the switch 34 opens and connects a resistor 36 into the feedback loop. , which causes the oscillations to cease.

Thus, the marking 30 according to Fig. 3 produces an oscillation signal when the antenna 31 receives a signal with a particular frequency and sufficient signal strength. This oscillation signal continues until it is interrupted by switch 34. Thus, the reader ll can send a signal for a short period of time and then listen for signals of the same frequency. If such a signal is sensed after the reader signal has ceased, this indicates that a mark corresponding to that frequency is present within the range of the reader 11.

Fig. 4 shows a more detailed embodiment of a marking 40 constructed according to the principle discussed in connection with the embodiment according to Fig. 3.

The mark 40 comprises an amplifier 41, the dry gain of which is determined within two resistors 42 and 43, which are connected between the output of the amplifier and the negative input and ground. The gain can, for example, be set to 10 times. Two diodes 44, 45 are connected in parallel and in opposite directions are connected to the positive input of the amplifier 41. The other end of the diodes 44, 45 are connected to an antenna 46 and to an LC tank circuit comprising an inductor 47 and a capacitor 48 tuned to a particular frequency.

The marking circuit according to Fig. 4 is operated as follows. Any signal on the antenna 46 will be shorted to ground via either the inductor 47 or the capacitor 48 and the output of the amplifier 41, which is at ground potential. However, a signal at the resonant frequency of the LC circuit will cause the LC circuit to oscillate. If the signal strength from the antenna 46 at said resonant frequency exceeds a predetermined value set by a knee voltage of the two diodes 44, 45 (normally about 0.8 volts), the signal passes to the positive input of the amplifier 41 and is amplified by the amplifier 41 and fed back. to the positive input via the LC circuit. The positive feedback causes the circuit to self-oscillate with an amplitude limited only by the supply voltage of the amplifier 41. The oscillations are radiated through the antenna 46. A switch 49 is connected across the resistor 42. If the switch 49 is closed, the gain of the amplifier 41 is greatly reduced and the oscillations will cease. A circuit, not shown in Fig. 4, controls the switch 49.

Fig. 5 describes a more general circuit diagram of a label 50. The circuit comprises an antenna 51 connected to a tank circuit comprising an inductor 52 and a variable capacitor or varactor 53. A voltage at the control line 54 controls the capacitance. The tank circuit includes a first resistor 54 (R), which substantially comprises the resistance of the metal wires of the inductor. A circuit 55 forming a negative resistance (s) is connected in series with the first resistor 54. An amplifier similar to that shown in Fig. 4 may form a negative resistance. The negative resistance 55 is variable in depending on the voltage across the resistance; a high voltage results in a higher value of the negative resistance. When the voltage is high enough, the negative resistance outweighs the first resistance and the circuit begins to self-seal. The antenna 51 transmits the oscillations. A threshold circuit 56 connected to a control circuit 57 also senses the oscillations. The control circuit 57 emits signals to the actuator 54 and to an attenuation switch 58 connected across the negative resistance 55. When the attenuation switch is closed, the oscillations cease. Furthermore, the control circuit generates a voltage controlling actuator 54, which will be described in more detail below.

F ig. 6 is a more detailed schematic diagram of an amplifier 60 with voltage-dependent gain, a warp amplifier. Amplifier 60 includes three transistors 60, 61, 62 and four resistors 63, 64, 65, 66 connected to form an amplifier. The output of transistor 61 is fed back to the input of transistor 60 in a positive feedback circuit, via an inductor 67 and a capacitor 68. During normal operation, without any input signal at the antenna 69, resistor 63 maintains the base of transistor 60 under a knee voltage of the transistor and practically no current passes through transistor 60. The same applies to resistor 64 and transistor 62, which also means that no current passes through transistor 61. The circuit is in a rest position draining virtually no current from the power supply.

The transistor 60 is in a position on a gain diagram shown in Fig. 7, in which the gain is below "one". However, if a signal appears at the antenna 69 with an amplitude sufficient to pass the transistor above the knee voltage, indicated by line 71, and into the range in which the gain is above the "one", the transistor 60 begins to draw current. As a result, the voltage across resistor 64 increases and transistor 62 begins to draw current as does transistor 61. The combination of transistors forms an amplifier with 180 degree phase shifts across each of transistors 60 and 61. The output (collector) of transistor 61 is fed back via inductor 67 and capacitor 68 to the input (base) of transistor 60. Thus, the circuit begins to self-oscillate at the frequency determined by inductor 67 and capacitor 68.

The circuit will resonate for antenna signals selected by an LC tank circuit comprising an inductor 75 and a capacitor 76 tuned to a first frequency (f1).

The LC tank circuit 75, 76 is isolated from the circuit 60-68 by a capacitor 64b. Such resonant signals will trigger the transistor 60 and initiate self-oscillations at a second frequency (f81, f82) determined by the inductor 67 and the capacitor 68.

The oscillations will cause the circuit to enter the saturation range indicated by line 72 in Fig. 7. A capacitor 64a is connected in parallel with the resistor. An output signal from the injection electrode of transistor 60 is supplied to a control circuit 79, which controls a switch 78 to attenuate the oscillations.

The circuit shown in Fig. 6 is thus operated in the sub-threshold error range of the transistors 60, 61, where practically no energy consumption occurs. Only when an antenna signal is received as described above does the circuit begin to consume energy.

Thus, the circuit always actively listens for radio signal without draining the power supply.

The circuit according to Fig. 6 can be said to be meta-stable, due to the fact that the gain in the positive feedback loop is below "one". When a signal over a particular arnplitud is received, the circuit becomes unstable. The gain increases to above "one" and the circuit begins to oscillate. The circuit is driven to self-oscillations with rapidly increasing hearth amplitude. However, the "propulsion" takes a certain time, until the self-oscillations begin, called the latency period.

Thus, the response time of the circuit may be in the range of a few microseconds, until the circuit has begun to self-oscillate. The LC circuit filters out signals that do not have the desired frequency so only a signal with a predetermined frequency and above a predetermined signal strength will trigger the circuit.

It is noted that an antenna signal with a frequency outside the predetermined center frequency will still trigger the circuit if it is close enough and has a sufficiently high signal strength.

Fig. 15 shows a circuit similar to that of the embodiment of Fig. 6 but without the first LC tank circuit 75, 76. Furthermore, a resistor 64c and a capacitor 64d have been added to stabilize the injection electrode of the transistor 61 during the oscillations. Furthermore, the capacitor 64d will form a ground path for the LC circuit 67, 68.

Fig. 8 shows a diagram of the Q-value of the circuit according to Fig. 5 or Pig. 6. At the center frequency, the Q-value is for example "two" when the circuit is in an area with maximum gain of the circuit, ie. on the straight line between lines 73 and 74 in Fig. 7. Thus, with an excitation frequency of fc, the circuit will begin to self-oscillate relatively rapidly. If the excitation frequency is in the frequency band between fl and f! however, the circuit will still start to self-oscillate (possibly with a longer latency period), because the gain will be above "one". However, as soon as the self-oscillation occurs, the oscillation frequency will shift relative to the center frequency fc. This property can be used and is called dissonance below.

Suppose the reader sends a signal with a frequency fl. Then any tag with a frequency band including the reader frequency will begin to self-oscillate and transmit a signal. The transmitted signal will be the center of the frequency of the tag. Thus, when the reader can send a signal with a frequency f1, which is indicated in Fig. G. 8, a signal with the frequency response 81 according to Figs. 8 to start oscillating around a frequency f8l and a marking with a frequency response 82 according to Fig. 8 will start to oscillate around a frequency f82.

The center frequency of a mark can be set from the beginning or be adjustable, for example as indicated in Fig. 5. A variable capacitor or a variable inductor can be used to cut off the circuit. A variable capacitor or varactor is well known and comprises a diode in which the width of the barrier layer between the p-doped and n-doped regions is controlled with a gate voltage. A variable inductor or capacitor can be constructed using one or more Switches to include one or more inductors or capacitors in the LC tank circuit.

The switches can be checked during or before operation. For example, the LC tank may be tuned to the reader frequency fl from the beginning and when a signal indicating self-oscillation is present at the output, another parallel capacitor may be switched to the circuit shifting the self-oscillation frequency to a lower value (f82), or another series capacitor may be switched into the circuit. the self-oscillation to a higher value (f8l).

Alternatively, the control circuit can adjust the LC tank before operation to an expected reader transmitter frequency. After receiving the reader signal and self-oscillation, the control circuit attenuates the circuit in which self-oscillation ceases. The control circuit can then shift the LC tank to a new expected frequency from the reader, which will be explained in more detail below.

Fig. 9 describes a marking device intended to be used to explain the operation below. The circuit comprises an antenna 91 providing signals to a selective filter circuit 92 with a resonant frequency which is adjustable by a voltage at a terminal 93. The signals selected with the filter circuit 92 are passed to an amplifier 94 with an adjustable gain. The gain is adjustable by a voltage at the terminal. 95. Furthermore, gain depends on the input signal strength, as explained above. The filter 92 and the amplifier 94 form a regenerative oscillator. When the regenerative oscillator oscillates, a signal appears at the output of the filter and this signal is sensed by a comparator 96, which may be an amplifier similar to amplifier 94, but without self-oscillating ability. The output signal of comparator 96 is supplied to a control circuit 97, which can produce an output signal to terminal 93 to control the resonant frequency and the output signal to terminal 95 to attenuate amplifier 94. Furthermore, a sensor or other input device 98 provides input signals. to the control circuit 97.

It is noted that the circuit system including comparator 96 can be made in the shape shown in Fig. 6 or 15 requiring virtually no energy during stand-by operation. The control circuit can be allowed to drain with energy from the battery as it is activated only at the request of the reader.

The control circuit comprises a register 99 comprising a series of frequencies which identify the label and are unique to each label.

The operation of the reader 11 to identify the presence of a specific label may be as follows: the label may have an identity vector (0, 15, 28, S) determined by a sequence of frequencies f0, f15, f28, f5.

The reader ll, see Fi g. L, sends a signal with a first frequency fi) (activation frequency). All markings include this frequency at the first (rest) frequency. Thus, all labels within range of the reader receive a signal of sufficient strength to trigger the oscillator and all labels send a retransmission signal for a period of time, after which the oscillations are attenuated by each label. At the same time, the control circuit is activated and shifts the resonant frequency of the filter to the second frequency of the label determined by its identity vector, in this case fl 5. Another label within reach of the reader shifts its frequency to its own second frequency determined by its identity vector.

If the reader receives at least one returned signal, this indicates that at least one label is within reach of the reader. Fl Your returned signals are often received.

Then the reader 11 sends a second signal at the second frequency f1 of the tag. A marking with this frequency will be triggered and begin to self-oscillate. This causes the control circuit of the relevant mark to attenuate the oscillations and shift the resonant frequency of the filter to a third frequency flS of the mark. For all labels that do not have fl as the second identity frequency, the control circuit will not receive any signals during the second transmission, resulting in the control circuit shifting the resonant frequency of the filter to the first frequency f0, whereupon the control circuit is deactivated. If the reader receives at least one retransmitted second signal, this indicates that at least one mark with fl 5 as the second identity frequency is within reach of the reader. Several returned signals can be received.

Then the reader ll sends a third signal at the third frequency fZS of the tag. A tag with this frequency and which has not been deactivated by the control circuit will be triggered and begin to self-oscillate. This forms the control circuit of the relevant marking to attenuate oscillations and shift the resonant frequency of the filter to the fourth frequency of the marking. For all labels not having f28 as the third identity frequency, the control circuit will not receive any signal during the third transmission, resulting in the control circuit shifting the resonant frequency of the filter to the first frequency f1), whereupon the control circuit is deactivated. If the reader receives at least one retransmitted third signal, this is an indication that at least one mark with fl5 as the second identity signal and f28 as the third identity frequency is within reach of the reader. A number of returned signals are received.

Finally, the reader 11 sends a fourth signal with a fourth frequency f5 of the tag. A mark with this frequency and which is not deactivated by the control circuit will be triggered and start self-oscillating. This causes the control circuit of the relevant marking to attenuate the oscillations. Only one label has this combination of frequencies. If that marking is within the reach of the reader ll, the reader ll will receive a retransmitted signal from that marking only.

The control circuit will have deactivated all other markings within reach of the reader by shifting the resonant frequency of the filter to the first frequency f1).

The reader can now send additional signals to the identified tag, for example to read values of an input signal provided by sensor 98, which may be a temperature sensor or any other device. Such interrogation of the relevant marking can occur at any frequency, which is not the first frequency f1). In another situation, the reader may be unaware of the identity of a label within the reach of the reader. Then some kind of mediation is required for the reader to obtain information about the identity of the marking area of the marking for the reader. This can take place as follows: The method uses the principle of dissonance, meaning that the marking responds to a frequency which deviates slightly from the reader frequency by a difference frequency fAl or fAZ.

First, the reader sends a signal at an activation frequency fl), see Fig. 10. All markings are originally tuned to this frequency from the beginning. Thus, all labels within range of the reader respond at a frequency that is fO plus fA1 or fA2.

If the reader receives a frequency of fO plus fAl, it shifts its frequency to a second frequency, which is fló. If the reader receives a frequency of fO plus fAZ, it shifts its frequency to a second frequency, which is f32. If both signals are received, the reader selects either of f16 or f32.

Then the reader sends a second signal at f16 (or f32) to which all the markings off for this frequency respond. If the reader receives a frequency of f16 plus fAl, it shifts its frequency to a second frequency that is f2O (l6 + 4). If the reader receives a frequency of fl 6 plus fA2, it shifts its frequency to a second frequency which is f24 (l6 + 8). If both signals are received, the reader selects either of f20 or f24. The non-responsive markings are deactivated by its control circuit.

Then the reader sends a third signal at f2O (or f24) whereupon all the markings tuned fdr this frequency respond. If the reader receives a frequency of f20 plus fAl, it shifts its frequency to a second frequency which is f21 (16 + 4 + l). If the reader receives a frequency of f20 plus fAZ, it shifts its frequency to a second frequency which is then í22 (l6 + 4 + 2). If both signals are received, the reader selects either of f21 or f22. The non-responsive markings are deactivated by its control circuit.

Finally, the reader l1 sends a fourth signal at f21 (or f22) to which all the markings tuned for this frequency respond. If the reader ll receives a frequency of t21 plus fA1 or F21 plus fA2, the reader will detect this.

Now the reader has l l four bits, which define the mark (fZl) which has responded to all the frequencies. Now the reader ll can query the marking at the selected frequency, which can be fll or any other frequency.

Then the reader can continue with the frequencies where it has received double responses.

In this way, the identity of the labels can be detected.

The sensor values can be detected with dissonance by allowing the sensor value to affect the difference frequency.

Other frequency schemes can be used, such as f0 as the first frequency, f1 or f5 as the second frequency, f1, fa, fS, f7 as the third frequency and f1, f2, f3, f4, fS, f6. f7, f8 were used to arbitrate between markings with fl «fB as the identity frequency, see Fig. 11. its control circuit.

The corresponding frequencies can be arranged as shown in Fig. 8 with f A1 = minus fA2 so that the two corresponding frequencies are centered around the trigger frequency fc. However, the detection of the corresponding frequencies by the reader can be difficult under these conditions. Thus, an arrangement where fA1 is different from fA2 would be possible, such as fA1 = minus 0.8 * fA2, see Fig. 12. Another arrangement would be that both corresponding frequencies above or below the triggering frequency fc, such as fA1 = fA2 or fA1 = 0.8 * fA2.

While two resonant frequencies can be used, such as three or four or more, fA1, fA2, fA3, fA4. .. Factor 0.8 could be another factor between 0 and 1.

The limitation is that all frequencies should be within the passband of the filter.

The filter has been shown as an LC tank circuit comprising an inductor and a capacitor. However, any filter circuit can be used which has a resonant frequency, i.e. a bandpass filter. Such filters may include MEMS circuits, a crystal filter, ceramic filters, LC filters with more than two components, active filters. In another embodiment, the receiving device shown can be used only for "awakening" of the marking. This embodiment is shown in Fig. 13. The device comprises an antenna 131. A bandpass filter 132 and a non-linear amplifier 133 are connected to form a regenerative oscillator which begins to oscillate when the signal from the antenna triggers the regenerative oscillator. A comparator senses the oscillations and controls a switch 135, which can switch on the power supply to control circuit 136. The control circuit emits a signal to the regenerative circuit to attenuate the oscillations by opening a switch 137 and including a resistor 138 in the oscillating circuit, whereby the oscillations end. . At the same time, the control circuit closes another switch 139 to the power supply of the control circuit.

The control circuit 136 includes another receiver 140 according to any well-known principle, such as a heterodynia receiver, which takes over the continued operation of the label. The receiver is connected to the antenna 131. When the operation is completed according to any algorithm, the control circuit deactivates itself by opening the switch 139 and the tag is returned to a deactivated state pending a new wake-up signal at the predetermined frequency.

The reader can send a single frequency signal or a broadband wake-up signal comprising several frequencies or a band of frequencies, such as a "Dirac" pulse. The labels that receive a signal at the predetermined frequency of sufficient signal strength will wake up. In this way, the marking will be in a low power position for a long time until a wake-up signal is received. If a spurious wake-up signal is received, the label will only wake up for a very short period of time, until the control circuit has verified that the wake-up signal is not a valid wake-up signal issued by a reader.

The reader can send a wake-up signal comprising a Bluetooth® interrogation sequence of frequencies as a wake-up signal. In this case, the embodiments according to F in g. 9 can be used to analyze the Bluetooth signal. If a correct sequence of signal is received, the control circuit is activated and takes over the control, for example according to any prior art method or any of the embodiments described above.

Fig. 14 shows another embodiment in which a plurality of regenerative circuits 142, 143 are connected to the same antenna 141. Each regenerative circuit comprises an attenuating switch 144 and 145, respectively. Two regenerative circuits 142, 143 are shown in Fig. 14, but any number can be used. The first regenerative circuit 142 is tuned to the frequency f81 corresponding to a logic "one" and the second regenerative circuit 143 is tuned to the frequency ñšZ corresponding to a logic "zero". a signal received by a sensor 147.

The operation for interrogating the marking is as follows. The reader has identified the marking in any way described above. The marking is interrogated at a frequency determined in advance, such as frequency fl indicated in Fig. 8.

The control circuit operates Switches 144 and 145 depending on the most significant bit of the sensor value of sensor 147, which may be a temperature sensor with an eight bit value intended to be sent to the reader. If the most significant bit is "one", switch 144 closes and switch 145 opens, if the most significant bit is "zero", switch 145 closes and switch 144 opens. Then the reader sends an interrogation signal at frequency fl. If the most significant bit is "one", regenerative circuit 142 begins to oscillate at frequency fl šl. If the most significant bit is "zero", regenerative circuit 143 begins to oscillate at frequency P82. The reader detects the answer. Then, the control circuit attenuates the oscillations and controls the switches 144 and 145 according to the next bit in the signal and the reader transmits a second interrogating signal at frequency f1, and so on.

After eight interrogation signals, all eight bits of the temperature signal have been sent to the reader.

The same principle can be used with a single regenerative circuit, the control circuit controlling a varactor or similar device depending on the sensor signal.

The embodiment with a number of regenerative receivers can be used to advantage also during identification as indicated above. Such an embodiment may have four control circuits, each tuned to the frequencies f0 + fAl, fl6 + fA1, t20 + fAl on fZ1 + fAl. as described above in connection with Fig. 10. If all four regenerative circuits are triggered in a sequence, the reader has received the identity of that label and can continue to query the label, for example as described above. The device according to any of the embodiments described above can be manufactured in a CMOS technology. However, other technologies can also be used, such as discrete components, for example MOSFET transistors with a very low energy consumption in the low power mode.

The embodiments can be incorporated into a computer software product which enables implementation of the method and functions described herein. The recovery can be performed when the computer software product is loaded and run in a system with computer capacity.

Computer programs, software programs, software products or software in the present context means any expression in any programming language, code or notation of a set of instructions intended to obstruct a system with processing capabilities to perform a particular function directly or after conversion to another language; code or listing.

Unless otherwise defined, all terms (including technical and scientific terms) as used herein have the same meaning as generally understood by one of ordinary skill in the art to which the present invention pertains. It should further be understood that terms, such as those defined in commonly used encyclopedias, should be interpreted to have a meaning consistent with their meanings in the context of the relevant technique and should not be construed in an idealized or overly formal sense unless expressly stated herein.

It should also be emphasized that the singular forms "en", "ett" and "de / den / det" used herein are intended to include the plural forms as well, unless the amiat is expressly stated. It is further understood that the terms "includes", "includes", "includes" and / or "includes", when used in this specification are assumed to specify the presence of said properties, units, steps, operations, elements, and / or components but exclude not the presence or addition of one or andra your other properties, units, steps, maneuvers, elements, components and / or groups thereof.

The present invention has been described above with reference to particular embodiments. However, embodiments other than those described above are equally possible within the scope of the invention. Different method steps than those described above, performing the method by hardware or software or a combination of hardware and software may be provided within the scope of the invention. The various features and steps of the invention may be combined in combinations other than those described. The various embodiments described above do not limit the scope of the invention, but the scope of the invention is limited only by the appended claims.

Claims (12)

l0 15 20 25 30 35 531 759 17 PATENT REQUIREMENTS A method of operating a device comprising a receiver (30), comprising: receiving a first signal having a first frequency from the receiver, the first signal being transmitted by a reader; characterized by operating the receiver in a metastable first operating state in a low power state with a low power consumption; and transmitting the receiver from the first metastable operating state to an oscillating second operating state upon receiving said first signal with said first frequency and with a signal strength above a threshold value; retransmitting a second signal with a second frequency after a latency period; interrupting said oscillations in said second oscillating operating state after a period of time by means of an extinguishing circuit. The method of claim 1, wherein said second frequency is the same as said first frequency. The method of claim 1, wherein said second frequency differs from said first frequency by a difference frequency. The method of claim 1, 2 or 3, further comprising: receiving transmitted signals with an antenna (31); passing said signals received by the antenna to a resonant circuit (32) tuned to a second frequency different from said first frequency; triggering said receiver circuit (30) with said signals if the signal strength after the resonant circuit (32) is above said threshold value; driving said receiver circuit (30) to, after said triggering, transmit a signal at said second frequency; and attenuating (34, 35) said receiver circuit or said time period so that the signal with the second frequency ceases. 10 15 20 25 30 35 531 799 18 The method of claim 4, further comprising: driving said receiver circuit in said metastable first operating state pre-trigger; and triggering, after triggering, said receiver circuit to self-oscillating with a signal strength of a predetermined value and with said second frequency; and attenuating said self-oscillation after said time period, thereby bringing the receiver circuit back to said low power state. A method according to any one of the preceding claims, wherein the returned signal activates a control circuit (57) for controlling the further function of the device. A method according to any one of the preceding claims, wherein said device is used in an article monitoring system (10) comprising a reader (11) and a plurality of identity markings (12, 13, 14, 15, 16). A wireless operating device, comprising: an antenna (31) for receiving signals transmitted by a reader (1 1); a resonant circuit (32) tuned to a first frequency for selecting a signal with said first frequency from the signals received by the antenna; a trigger circuit (36) for receiving said selected signal; an oscillation circuit (33, 32, 36) biased for operation in an inactive, metastable first operating state in a low power state with a low power consumption and operated by said trigger circuit to start oscillating at a second frequency upon triggering depending on receiving a signal with said first frequency and a signal strength above a threshold value; and an extinguishing circuit (34, 35) for interrupting said oscillations after a period of time. The device of claim 8, wherein said first frequency is equal to said second frequency. The device of claim 8, wherein said first frequency differs from said second frequency by a difference frequency. 53 '1 795 19 The apparatus of any of claims 8 to 10, further comprising: a control circuit (57) for receiving an input signal and adjusting said second frequency depending on said input signal. Device according to any one of claims 8 to 11, wherein the device is used in an article monitoring system (10) comprising a reader (11) and a plurality of identity markings (12, 13, 14, 1 5, 16).