Circuit for a passive radio frequency identification tag comprising an inclination sensor and method for manufacturing the circuit

Abstract

The present invention relates to a circuit (1) for a passive radio frequency identification tag operating in the UHF band, configured for wireless communication with a reader that emits a read signal. The circuit is fabricated as a single chip comprising one or more transducers for measuring strain, a first sub-circuit (43) configured to acquire transducer measurements, and a second sub-circuit (2, 3) configured to wirelessly transmit the acquired measurements to the reader. Furthermore, the present invention relates to a system and method.

Description

Technical Field

[0001] The present invention relates to a contactless device, for example in the form of an RFID device, comprising a sensor for recording events over a long period of time without the need for an external power supply. The invention relates in particular to a circuit for a passive radio identification tag operating in the UHF band, which includes a power recovery phase and a communication phase, and which is configured to communicate wirelessly with a reader that emits periodic reading signals.

Background Art

[0002] In a manner known in the prior art, a circuit in the form of an RFID (Radio Frequency Identification) can function as an RFID tag, also known as a marker, and can be combined with an object to be monitored. The circuit includes a sensor for measuring at least certain physical parameters related to this object, such as, for example, ambient temperature, humidity, or acceleration, or optionally is connected to such a sensor by an interface.

[0003] The circuit generally takes the form of an adhesive label that is adhered to the object to be monitored or to a device integrated into the object to be monitored. The object to be monitored is, for example, an industrial device, a commodity, a product, or an organism that needs to be monitored by measuring at least one physical parameter.

[0004] Generally, such a contactless device includes a memory storage module capable of storing measurement values acquired by a measurement module, an antenna capable of transmitting these measurement values to an interrogator via an electromagnetic signal, and in particular a power source for supplying the measurement module.

[0005] Such systems customarily include an RFID reader or interrogator and a contactless device equipped with an RFID circuit (or tag) (or multiple circuits) that is attached to or fixed to the object to be tracked. The RFID reader generally emits a UHF signal, also known as an interrogation signal, to the RFID circuit. The use of the UHF signal has the following advantages, namely high communication speed and the possibility of communicating with multiple tags simultaneously.

[0006] For this purpose, the contactless device includes one or more sensors for measuring at least one physical parameter. The sensor can be configured as a transducer that converts a certain physical signal into another physical signal, such as converting mechanical strain into electricity.

[0007] Many types of sensors are known. For example, a strain sensor is described by B. Rue, B. Olbrechts, J.-R. Raskin and D. Flandre, ‘‘A SOI CMOS smart strain sensor,’’ IEEE 2011 International SOI Conference, Tempe, AZ, 2011, pp. 1-2. Such a strain sensor can be used to measure the deformation or strain of the object under surveillance.

[0008] The RFID tags used in these systems are customarily passive tags, that is, they do not include a battery or power storage means. These tags use the power contained in the carrier wave of the reader signal to send a modulated version of the reader signal back to the RFID reader. At least a part of the power of the interrogation signal is recovered by a power collection device and supplied to the components of the tag. Passive tags have the advantages of being lightweight, hassle-free, and having a long lifespan.

[0009] Passive RFID tags are described, for example, in French Patent Application Publication No. 3015729 or explained by C. Felini et al., “Fully RF Powered UHF-RFID Sensors Platform,” Procedia Engineering 87 (2014) 1346-1349. RFID tags are also known from U.S. Patent Application Publication No. 20080136619, U.S. Patent Application Publication No. 20130099897, U.S. Patent No. 6720866, Chinese Patent Application Publication No. 104361388, U.S. Patent No. 9789738, or U.S. Patent Application Publication No. 20100231407.

[0010] However, the combined use of a UHF interrogation signal and a passive tag has the drawback that the power recovered by the passive tag is limited, resulting in a short read range, for example less than 20 cm (especially when the circuit is connected to a sensor). In this situation, the use of an external sensor connected to the circuit by an interface can consume most of the power, especially when the sensor has individual electronic devices (or digital components), the interface is a digital interface (e.g., SPI or I2C), and / or the channels for acquiring the signals of the external sensor consume excessive power. Furthermore, the read time can become extremely long, for example lasting more than 500 ms. Additionally, a system comprising a circuit and an external sensor connected by an interface can increase in mass and size when a digital interface is used.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

[0012] [Non-Patent Document 1] B. Rue, B. Olbrechts, J.-R. Raskin and D. Flandre, ‘‘A SOI CMOS smart strain sensor,’’ IEEE 2011 International SOI Conference, Tempe, AZ, 2011, pp. 1-2 [Non-Patent Document 2] C. Felini et.al. ‘‘Fully RF Powered UHF-RFID Sensors Platform’’, Procedia Engineering 87(2014)1346-1349 [Summary of the Invention]

[0013] An object of the present invention is to reduce all or part of the above-mentioned drawbacks, and in particular, to enable rapid strain measurement with low power consumption. Further, the present invention has an object of enabling a non-contact device including a circuit and an external sensor connected by an interface having a small size and a reading distance as long as, for example, 5 meters. Further, the present invention aims to comply with the EPC UHF Gen 2 Air Interface protocol.

[0014] For this purpose, the present invention provides a circuit for a passive radio identification tag operating in the UHF band, configured to wirelessly communicate with a reader that emits a read signal. The circuit is manufactured as a single chip including one or more transducers for measuring strain, a first sub-circuit configured to acquire transducer measurement values, and a second sub-circuit configured to wirelessly transmit the acquired measurement values to the reader.

[0015] The chip (or die) can be considered as a single integrated circuit and / or a single chip, and furthermore, or the transducers, the first sub-circuit, and the second sub-circuit are integrated into the chip (within the same integrated circuit).

[0016] As a result, by integrating the transducers into the chip together with the first and second sub-circuits, the measurement values can be acquired and transmitted to the reader more quickly (e.g., within 1500 μs or less) with low power consumption (e.g., 1 μA or less). Therefore, it is possible to extend the read distance, for example, up to a maximum of 5 meters (especially due to the reduction in consumption), and to reduce the size of the contactless device.

[0017] The transducer can be considered, for example, as a piezoresistive strain sensor, and furthermore, or the transducer can be configured to measure the mechanical strain applied to the circuit, and furthermore, or the transducer can include at least one strain sensor provided by two transistors sensitive to orthogonal strains, and furthermore, or the transducer can include at least one positive current fluctuation strain sensor and at least one negative current fluctuation strain sensor, and furthermore, or the transducer can include two or more series-connected strain sensors.

[0018] By using orthogonal transistors, it becomes possible to measure the strain covering along two directions in the XY plane of the component.

[0019] In particular, the transducer can comprise at least one such positive current-varying strain sensor and at least one such negative current-varying strain sensor.

[0020] For example, the transducer can comprise two (or more) positive current-varying strain sensors in series and two (or more) negative current-varying strain sensors in series.

[0021] By using strain sensors in series, it becomes possible to improve (multiply) the sensitivity of the transducer for measuring strain.

[0022] The first sub-circuit can comprise an element (a first one) configured to supply a supply current to the transducer. This element can optionally set a bias current with a predetermined current gain.

[0023] The first sub-circuit can further comprise an element (a second one) configured to perform common-mode current cancellation of the output signals of the transducer or of each positive / negative current-varying strain sensor. This makes it possible to consider only the current resulting from the variation of the transducer signal excluding the common mode. Thus, the range of the measurement signal can be increased.

[0024] When the transducer comprises a positive current-varying strain sensor and a negative current-varying strain sensor, the first sub-circuit can comprise an element (a third one) configured to generate a differential signal between the output signals of these two strain sensors, in particular after canceling the common-mode currents respectively. This further enables an increase in the range of the measurement signal.

[0025] The first sub-circuit can comprise an I / V converter configured to convert the output signal or the actuation signal of the transducer.

[0026] The I / V converter may be configured to convert a current signal into a voltage signal.

[0027] The I / V converter may be a passive converter and may be configured to generate a differential voltage signal.

[0028] Accordingly, the converter enables it to be based on a voltage signal instead of the original current signal.

[0029] The first sub-circuit may include an analog-to-digital converter (ADC) configured to digitize the transducer measurement, particularly the output signal of the I / V converter. This digitized signal can be received by a command device of the circuit (and / or the second sub-circuit) and transmitted to a reader (e.g., by an antenna).

[0030] The reader can emit a periodic read signal including a power recovery phase and a communication phase. The circuit, particularly the second sub-circuit, may include a command device configured to accumulate a power reserve from radio waves in the power recovery phase and communicate with the reader in the communication phase. The power recovery phase may include an acquisition phase in which the circuit supplies power to the transducer, acquires the transducer measurement, performs I / V conversion, and digitizes it.

[0031] The command device can be further configured to transmit the digitized transducer measurement to the reader in the communication phase of the same period.

[0032] During the power recovery phase, and thus before the communication phase, and thus during a single period of the periodic read signal, the measured values can be acquired, converted, and digitized in the acquisition phase. Therefore, these measured values can be transmitted directly to the reader during this communication phase, i.e., during the same period. As a result, the response time of the circuit can be shortened. Therefore, it is possible to read (query) several external circuits very quickly. For example, objects equipped with the circuit according to the invention can be grouped together in a crate and each can be read very quickly.

[0033] The circuit can further comprise an interface for connecting (at least) one external analog sensor. The interface can comprise an electrical connection configured to electrically connect and supply power to the external analog sensor and acquire the analog measurement value of the sensor, and an amplifier configured to amplify the signal of the analog measurement value of the sensor. An analog-to-digital converter (ADC) can be configured to digitize the amplified analog measurement value of the sensor. The power recovery phase can include an acquisition phase in which the interface supplies power to the external analog sensor and acquires, amplifies, and digitizes the measurement value of the sensor.

[0034] The command device can be further configured to supply power to the interface to acquire the amplified and digitized measurement values in the acquisition phase and transmit the amplified and digitized measurement values to the reader in the communication phase of the same period.

[0035] As a result, such an interface allows directly connecting to the circuit an analog sensor that consumes less power as compared with a digital sensor with additional electronic components / circuits. Further, during the power recovery phase, thus before the communication phase, and thus during a single period of the periodic read signal, in the acquisition phase, the measured value of the sensor can be acquired, amplified, and digitized, so that this measured value can be directly transmitted to the reader during this communication phase, i.e., during the same period. As a result, the response time of the circuit can be shortened. Thus, it is possible to very quickly read (query) several external circuits. For example, objects provided with a circuit according to the invention can be collectively arranged in a crate and each can be very quickly read. According to another example, it is possible to measure the pressure of a tire when a vehicle passes in front of a gate.

[0036] The command device can be configured to boot during the boot phase, which is before the acquisition phase and during the same power recovery phase.

[0037] The power recovery phase can include, before the boot phase, an initial power recovery phase in which the circuit is turned off and power reserves are accumulated exclusively from radio waves.

[0038] As a result, since the accumulated power level is high enough, a reliable boot can be guaranteed.

[0039] The power recovery phase can further include, between the boot phase and the acquisition phase, a first intermediate power recovery phase in which the circuit is turned off and power reserves are accumulated exclusively from radio waves.

[0040] As a result, since the accumulated power level is high enough, a reliable acquisition of the measured value can be guaranteed.

[0041] The power recovery phase can further include a second intermediate power recovery phase that turns off the circuit and accumulates a reserve of power solely from radio waves, after the acquisition phase and before the communication phase.

[0042] As a result, since the level of the accumulated power is high enough, reliable transmission of the measured values to the reader can be ensured.

[0043] The command device can optionally be configured to supply the interface solely in the acquisition phase.

[0044] As a result, the interface can supply power to the analog sensor. Further, if the interface operates solely in the acquisition phase, power consumption can be reduced.

[0045] The command device is optionally configured to sequentially supply electricity to the elements of the interface, such as by supplying electricity to an analog sensor, an amplifier, and an analog-to-digital converter (ADC) in sequence.

[0046] As a result, each element is supplied with electricity only at the moment when it is necessary to perform measurements solely, so instantaneous power consumption can be reduced.

[0047] Therefore, the command device can be configured to supply power to the electrical connection part solely to obtain the analog measurement value of the sensor by first supplying power to the external analog sensor, and then supply power to the analog-to-digital converter (ADC) solely to digitize the amplified analog measurement value of the sensor.

[0048] After digitization of the measured value by the analog-to-digital converter (ADC) and during the acquisition phase, the digitized measured value is read by the command device and stored in the memory.

[0049] In this way, the measured value is in a state where it is ready to be transferred to the reader at the start of the communication phase.

[0050] The circuit is, for example, compatible with (or communicates according to) the EPC UHF Gen 2 Air Interface protocol.

[0051] Furthermore, the present invention provides a passive radio identification system operating in the UHF band, comprising a reader that emits a periodic read signal, the period of the read signal including a power recovery phase and a communication phase, and a circuit as described above.

[0052] Furthermore, the present invention provides a method for manufacturing a circuit for a passive radio frequency identification tag operating in the UHF band and configured to wirelessly communicate with a reader that emits a read signal. The circuit is manufactured as a single chip comprising at least one transducer for measuring strain, a first sub-circuit for acquiring transducer measurement values, and a second sub-circuit for wirelessly transmitting the acquired measurement values to the reader.

[0053] The manufactured circuit can also have the above-described characteristics within the range of a non-contact device.

[0054] The features and advantages of the present invention will become apparent by considering the following description given with reference to the accompanying drawings, which are provided as non-limiting examples of the present invention.

Brief Description of the Drawings

[0055]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0056] Figure 1 is a schematic diagram of the architecture of circuit 1 according to the present invention. Circuit 1 is an RFID - type circuit operating in the UHF band and can function as an RFID tag. The circuit is, for example, compatible with (or communicates according to) the EPC UHF Gen 2 Air Interface protocol.

[0057] The circuit takes the form of, for example, an adhesive tag adhered to the object to be monitored or a chip integrated into the object to be monitored. The object to be monitored is, for example, a commodity, product, or organism that needs to be monitored by measuring at least one physical parameter, particularly the mechanical strain (voltage, deformation, or stress) applied to the object and thus to the circuit.

[0058] The circuit is fabricated as a single chip, i.e., as an integrated circuit or a "die".

[0059] Circuit 1 operates passively, i.e., it does not include a battery or power storage means. However, it uses the power contained in the carrier wave of the reader's signal to send back a modulated version of the reader signal to the RFID reader. At least a part of the power of the interrogation signal is recovered by the power collection device and supplied to the components of the circuit. Specifically, Circuit 1 includes an analog module 2 connected to antenna 21, recovers the power received by the antenna from the radio waves emitted by an external reader, and receives and transmits communication signals.

[0060] For this purpose, the analog module 2 comprises a modulation unit 22 (for example, for transmitting a communication signal). Furthermore, it comprises a demodulation unit 25 (for example, for receiving a communication signal). Furthermore, it comprises a rectification unit 23 and a supply control unit 24 for continuously and / or accumulating a power reserve from radio waves in the power recovery phase. The rectification unit 23 can convert the wireless power into DC power and supply it to the circuit. Furthermore, the supply control unit 24 can generate a DC current for supplying a bias current (optionally with a given current gain) to the transducer and, optionally, also generate a "clean" DC voltage for supplying to the interface 4. For example, the accumulated power can be stored in a capacitance (for example, a capacitor).

[0061] A digital module 3 (or a command device 3) is connected to the analog module 2. This digital module 3 comprises a processor and / or a memory storage unit 31 that can process data and / or an external analog sensor. Furthermore, the digital module optionally comprises digital interfaces 32, 34, such as SPI or I2C, and / or an interrupt interface 33. The digital module 3 controls the analog module 2, for example, to supply the accumulated power and communicate with the reader via the antenna 21. Therefore, the accumulation, consumption, and storage of power are controlled by the digital module 3 (see the description regarding FIG. 2 below).

[0062] The analog module 2 and the digital module 3 can cooperate to form a second sub-circuit according to the present invention for wirelessly transmitting the transducer measurement values to the reader.

[0063] Circuit 1, for example, analog module 2, further includes a circuit (or transducer circuit) 5 for measuring strain. Therefore, the transducer is integrated into the chip of the circuit. The transducer may be, for example, a strain sensor embodied by two transistors sensitive to piezoresistive orthogonal strain. The transducer and the (first) sub-circuit for acquiring transducer measurement values are described in detail in relation to FIG. 2.

[0064] The circuit further includes an analog-to-digital converter (ADC) 43 configured to digitize the amplified analog transducer measurement values, particularly the (first) sub-circuit. The signal output from converter 43 is sent to digital module 3 and transmitted to the memory and the reader. The converter can be connected to oscillator 28 to receive the clock signal "CLK".

[0065] The circuit may further include other internal analog sensors (for example, for temperature measurement) connected to, for example, converter 43.

[0066] Furthermore, digital module 3 is optionally connected to an interface (or interface module) 4. Interface 4 includes an electrical connection part 41 configured to electrically connect and supply an external analog sensor and acquire the analog measurement value of the sensor. Furthermore, it includes an amplifier 42 configured to amplify the signal of the analog measurement value of the sensor. The analog-to-digital converter (ADC) 43 is also configured to digitize the amplified analog measurement value of the sensor.

[0067] FIG. 2 is a schematic diagram of a transducer circuit according to the present invention.

[0068] As shown in FIG. 2, the transducer 51 can include at least one strain sensor embodied by two transistors sensitive to orthogonal strains. In particular, in the example of FIG. 2, the transducer includes two (or more) positive current fluctuation strain sensors 51c, 51d in series and two (or more) negative current fluctuation strain sensors 51a, 51b in series.

[0069] Circuit 1, for example, analog module 2, includes an element 55 for setting a bias current and an element 56 for applying a gain to the bias current. These elements 55, 56 supply this supply current to the transducer. These elements 55, 56 can cooperate to form the first element of the present invention.

[0070] Circuit 1, for example, analog module 2, further includes a second element 52 (common mode current cancellation) configured to perform common mode current cancellation of the output signal of the transducer 51. For this purpose, this element includes two sub-elements 52a, 52b. This makes it possible to be based only on the current resulting from the variation of the signal of the transducer excluding the common mode. Therefore, the range of the measurement signal can be increased.

[0071] Circuit 1, for example, analog module 2, further includes a third element 53 configured to generate a differential signal between the output signals of two orthogonal strain sensors, particularly after canceling the common mode current by the element 52 respectively. This further enables an increase in the range of the measurement signal.

[0072] Circuit 1, for example, analog module 2, further includes a current / voltage (I / V) converter 54 configured to convert the differential output signal of element 53 and convert a current signal into a voltage signal. The I / V converter 54 may be a passive converter and may be configured to generate a differential voltage signal. Thus, the converter enables it to be based on a voltage signal instead of the original current signal. The output signal of the I / V converter 54 is sent to an analog-to-digital converter (ADC) 43.

[0073] Elements 55, 56, 52, 53, I / V converter 54, and analog-to-digital converter (ADC) 43 can cooperate to form a first sub-circuit configured to obtain transducer measurement values according to the present invention.

[0074] Figure 3 is a schematic diagram of the power recovery phase according to the present invention. The figure shows four activities (or four sub-diagrams), and its X-axis represents time.

[0075] An external reader issues a periodic read signal. One period P of the read signal includes a power recovery phase REC and a communication phase COM. In the power recovery phase REC, power reserves are accumulated from the radio waves of the external reader. The power recovery phase REC includes the phases described below.

[0076] As shown in the sub-diagram of "RF harvesting", in the phase of initial power recovery, no element or unit of the circuit is active, and thus all power is stored, so it increases (e.g., at 5 microwatts for 500 microseconds).

[0077] Thereafter, that is, when sufficient power for reliable operation is stored, the digital module 3 is booted in the boot phase (e.g., with a consumption of 6 microwatts over 250 microseconds). At the same time, due to this operation of the digital module 3, the stored power decreases.

[0078] For this reason, after the boot phase, the power recovery phase includes a first phase in which no element or unit of the circuit is active and thus all power is stored, so the stored power increases again (e.g., to 5 microwatts over 100 microseconds) to recover the intermediate power.

[0079] Thereafter, i.e., when sufficient power is stored to enable reliable operation, in the acquisition phase ("acquisition"), the transducer measurement value 51 is acquired and digitized (optionally, interface 4 powers an external analog sensor, acquires, amplifies, and digitizes the sensor's measurement value) (e.g., with a consumption of 6 microwatts over 250 microseconds). At the same time, this operation of digital module 3 decreases the stored power.

[0080] For this reason, after the acquisition phase, the power recovery phase includes a second phase in which no element or unit of the circuit is active and thus all power is stored, so the stored power increases again (e.g., to 5 microwatts over 100 microseconds) to recover the intermediate power.

[0081] Thereafter (or after another predetermined period), the power recovery phase can be terminated and the communication phase COM can be started. In the communication phase, i.e., during the same period, the measurement value is transferred to an external reader.

[0082] Figure 4 is a schematic diagram of the power acquisition phase ACQ according to the present invention. The figure shows eight activities (or eight sub-diagrams), and its X-axis represents time. In the power acquisition phase ACQ, power is sequentially supplied to the elements of the interface 4. As shown in the sub-diagram of "SENSOR_EN", first, power is supplied only to the transducer 51 (and optionally an electrical connection, thus an external analog sensor) (for example, over 1 microsecond), and the signal generated by the transducer (and optionally the sensor) is read and sampled. Thereafter, as an optional phase, power is supplied only to the amplifier 42 to amplify the signal of the analog measurement value of the sensor (see the sub-diagram of "AMP_EN"). Next, power is supplied only to the analog-to-digital converter (ADC) 43 to digitize the analog measurement value (see the sub-diagram of "ADC_EN"). After the digitization of the measurement value by the analog-to-digital converter (ADC), and more preferably during the acquisition phase, the digitized measurement value is read and stored by the processor 31, and thus becomes available for use by the digital module 3 (see the sub-diagram of "DATA_RDY").

[0083] Due to this sequential operation, the total consumption for obtaining the amplified and digitized measurement values can be reduced, for example, to 1 microwatt. For this reason, it is possible to perform the acquisition and transmission of the measurement values during a single period of the signal of the reader.

Claims

1. A circuit (1) operating in the UHF band, configured to wirelessly communicate with a reader that emits a reading signal, comprising: at least one transducer (51) comprising at least one mechanical strain sensor for measuring strain; a first sub-circuit (52, 53, 54, 55, 56, 43) configured to obtain transducer measurement values; and a second sub-circuit (2, 3) configured to wirelessly transmit the obtained measurement values to the reader, manufactured as a single chip.

2. The chip consists of a single integrated circuit and / or a single chip, and furthermore / or the transducer (51), the first sub-circuit (52, 53, 54, 55, 56, 43), and the second sub-circuit (2, 3) are integrated into the chip. The circuit according to claim 1.

3. The transducer is particularly a piezoresistive strain sensor, and furthermore / or the transducer comprises at least one strain sensor embodied by two transistors sensitive to orthogonal strain, and furthermore / or the transducer comprises at least one positive current-varying strain sensor and at least one negative current-varying strain sensor, and furthermore / or the transducer comprises two or more strain sensors in series. The circuit according to claim 1 or 2.

4. The first sub-circuit comprises elements (55, 56) configured to supply supply current to the transducer. The circuit according to any one of claims 1 to 3.

5. The first sub-circuit comprises an element (52) configured to perform common-mode current cancellation of the output signal of the transducer. The circuit according to any one of claims 1 to 4.

6. When the transducer comprises a positive current-varying strain sensor and a negative current-varying strain sensor, the first sub-circuit comprises an element (53) configured to generate a differential signal between the output signals of the two positive and negative strain sensors, particularly after canceling the common-mode currents respectively. The circuit according to any one of claims 1 to 5.

7. The first sub-circuit includes an I / V converter (54) configured to convert the output signal of the transducer or to convert the differential signal. The circuit according to claim 6. **Claim 8** The I / V converter is configured to convert a current signal into a voltage signal, and / or the I / V converter is a passive converter configured to generate a differential voltage signal. The circuit according to claim 7. **Claim 9** The first sub-circuit includes an analog-to-digital converter (ADC) (43) configured to digitize the transducer measurement value, in particular the output signal of the I / V converter. The circuit according to claim 7 or 8. **Claim 10** The reader emits a periodic reading signal including a power recovery phase and a communication phase. The circuit, in particular the second sub-circuit, includes a command device (31) configured to accumulate a power reserve from radio waves during the power recovery phase and to communicate with the reader during the communication phase. and The power recovery phase includes an acquisition phase in which the circuit supplies power to the transducer (51), acquires a measurement value of the transducer (51), performs I / V conversion, and digitizes it. The circuit according to any one of claims 1 to 9. **Claim 11** The command device (31) is further configured to transmit the digitized measurement value of the transducer to the reader during the communication phase of the same period. The circuit according to claim 10. **Claim 12** The circuit further includes an interface (4) for connecting an external analog sensor. The interface includes an electrical connection part configured to electrically connect and supply power to the external analog sensor and to acquire an analog measurement value of the analog sensor, and an amplifier (42) configured to amplify the signal of the analog measurement value of the analog sensor. and The analog-to-digital converter (ADC) (43) configured to digitize the measurement value of the transducer is configured to digitize the amplified analog measurement value of the analog sensor. The command device (31) supplies power to the interface in order to acquire the amplified and digitized measurement value of the analog sensor during the acquisition phase, and transmits the digitized measurement value to the reader during the communication phase of the same period. further configured as the circuit according to claim 11.

13. the command device is configured to boot in a boot phase wherein the boot phase is before the acquisition phase and during the same power recovery phase the circuit according to any one of claims 10 to 12.

14. the power recovery phase includes, before the boot phase, a phase of turning off the circuit and accumulating only power reserves from the radio wave for initial power recovery the circuit according to claim 13.

15. the power recovery phase further includes, between the boot phase and the acquisition phase, a first intermediate power recovery phase of turning off the circuit and accumulating only power reserves from the radio wave the circuit according to claim 11 or 12.

16. the power recovery phase further includes, after the acquisition phase and before the communication phase, a second intermediate power recovery phase of turning off the circuit and accumulating only power reserves from the radio wave the circuit according to any one of claims 11 to 13.

17. the command device is configured to supply only to an interface for connecting an external analog sensor in the acquisition phase the circuit according to claim 10.

18. A passive radio identification system operating in the UHF band, a reader that emits a periodic read signal, the period of the read signal including a power recovery phase and a communication phase, and the circuit according to any one of claims 1 to 17 a passive radio identification system comprising the same.

19. A method for manufacturing a circuit (1) for a passive radio frequency identification tag operating in the UHF band, configured to wirelessly communicate with a reader that emits a read signal, wherein the circuit is manufactured as a single chip comprising at least one transducer (51) for measuring strain, a first sub-circuit (52, 53, 54, 43) for acquiring transducer measurement values, and a second sub-circuit (2, 3) for wirelessly transmitting the acquired measurement values to the reader.

Images