WO2024241175A1

WO2024241175A1 - Multi-band passive rfid tag

Info

Publication number: WO2024241175A1
Application number: PCT/IB2024/054816
Authority: WO
Inventors: Ali Shaji; Mohammadjavad HAJIKHANI
Original assignee: Inlan Inc.
Priority date: 2023-05-19
Filing date: 2024-05-17
Publication date: 2024-11-28

Abstract

There is described a radio-frequency identification (RFID) tag comprising: a substrate; at least one antenna for receiving an unmodulated power signal having a first frequency and a modulated interrogation signal having a second frequency being different from the first frequency, and transmitting a modulated response signal having a third frequency, the third frequency being one of a harmonic and a subharmonic of the first frequency; a storing unit for storing tag data; a signal processing unit for: extracting interrogation information from the modulated interrogation signal; generating the modulated response signal based on the tag data, the interrogation information and a first part of the unmodulated power signal; transmitting the modulated response signal via the at least one antenna; and converting a second part of the unmodulated power signal into a DC electrical signal for powering the RFID tag.

Description

MULTI-BAND PASSIVE RFID TAG

FIELD

[0001] The present technology pertains to the field of radio-frequency identification (RFID) tags, and more particularly to passive RFID tags.

BACKGROUND

[0002] Today, passive RFID tags are widely used for digital identification. Unlike QR codes, passive RFID tags can be read at a distance, and many tags can be read almost instantly without needing a line-of-sight view between the tag and the reading device. These two features make passive RFID technology very favorable for a wide range of applications in the industry.

[00031 The maximum distance from which a tag can be read is called the read range. The percentage of the tags that can be read successfully is called read yield. Increasing the read range and read yield of RFID tags are crucial in evaluating the system's overall performance. In order to improve these parameters, the signal coming from the tag needs to be enhanced in comparison with the noise and interference in the system.

[0004] One of the main obstacles to improving signal to interference and noise ratio in conventional passive RFID tags is the self-jamming problem. When it tries to read an RFID tag, a reader illuminates the tag by radiating a radiofrequency (RF) signal. The RFID tag usually reflects the signal back to the reader while embedding low-bandwidth data on the reflected signal. In conventional RFID systems, the transmitted signal from a reader and the reflected signal from an RFID tag use the same carrier frequency. This setup can cause the strong signal coming from the reader to jam the reflected signal coming back from the RFID tag. [0005] Besides regulatory guidelines, self-jamming is one of the main problems that puts practical limits on the reader's maximum transmission power. Increasing the reader's transmission power in conventional RFID systems would only lead to further burying of the tag's response. On the other hand, since passive RFID tags backscatter readers' signals, readers' lower transmission power means a shorter read range and lower read yield for the system.

[0006] Therefore, there is a need for an improved RFID system.

SUMMARY

[0007] According to a first broad aspect, there is provided a radio-frequency identification (RFID) tag comprising: a substrate; at least one antenna for receiving an unmodulated power signal having a first frequency and a modulated interrogation signal having a second frequency being different from the first frequency, and transmitting a modulated response signal having a third frequency, the third frequency being one of a harmonic and a subharmonic of the first frequency; a storing unit for storing tag data; a signal processing unit for: extracting interrogation information from the modulated interrogation signal; generating the modulated response signal based on the tag data, the interrogation information and a first part of the unmodulated power signal; transmitting the modulated response signal via the at least one antenna; and converting a second part of the unmodulated power signal into a DC electrical signal for powering the RFID tag, wherein the at least one antenna, the signal processing unit and the storing unit are mounted to the substrate.

[0008] In one implementation, the signal processing unit comprises: a demodulator for extracting the interrogation information from the modulated interrogation signal; an AC- to-DC converter for converting the second part of the unmodulated power signal into a DC electrical signal; a processor for receiving the interrogation information and generating a response data signal based on the tag data and the interrogation information; and a modulator and a frequency- shifting component for modulating the first part of the unmodulated power signal according to the response data signal and converting the first frequency to the third frequency.

[0009] In one implementation, the modulator is configured for receiving and modulating the first part of the unmodulated power signal according to the response data signal to obtain a modulated carrier signal and the frequency-shifting component is configured for changing the first frequency of the modulated carrier signal to the third frequency to obtain the modulated response signal.

[0010] In one implementation, the frequency-shifting component is configured for receiving the first part of the unmodulated power signal and changing the first frequency of the first part of the unmodulated power signal to the third frequency to obtain a frequency- shifted signal, and the modulator is configured for modulating the frequency- shifted signal according to the response data signal to obtain the modulated response signal.

[001 1 ] In one implementation, the AC-to-DC converter comprises a first rectifier.

[0012] In one implementation, the frequency-shifting component comprises non-linear component.

[0013] In one implementation, the non-linear component comprises one of a diode and a second rectifier.

[0014] In one implementation, the signal processing unit comprises: a demodulator for extracting the interrogation information from the modulated interrogation signal; a rectifier for converting the second part of the unmodulated power signal into a DC electrical signal and changing the first frequency of the first part of the unmodulated power signal to the third frequency to obtain a frequency-shifted signal; a processor for receiving the interrogation information and generating a response data signal based on the tag data and the interrogation information; and a modulator for modulating the frequency-shifted signal according to the response data signal to obtain the modulated response signal.

[0015] In one implementation, the at least one antenna comprises one of a single antenna, two antennas and three antennas. [0016] In one implementation, the at least one antenna comprises one of a single antenna, two antennas and three antennas.

[0017] In one implementation, the at least one antenna further receives a second modulated interrogation signal having the first frequency, and transmits a second modulated response signal having the first frequency.

[0018] In one implementation, the signal processing unit further: extracts a second interrogation information from the second modulated interrogation signal; generates the second modulated response signal based on the tag data, the second interrogation information and a first part of the second modulated interrogation signal; transmits the second modulated response signal via the at least one antenna; and converts a second part of the second modulated interrogation signal into a DC electrical signal to power the RFID tag.

[0019] In one implementation, the signal processing unit comprises: a demodulator for extracting the second interrogation information from the second modulated interrogation signal; a rectifier for converting the second part of the second modulated interrogation signal into the DC electrical signal; a processor for receiving the second interrogation information and generating a response data signal based on the tag data and the interrogation information; and a modulator for modulating the second modulated interrogation signal according to the response data signal to obtain the second modulated response signal.

[0020] According to another broad aspect, there is provided a radio-frequency identification (RFID) system comprising: a reader comprising at least one antenna, a signal processing unit and a storing unit, the processing unit being configured for generating an unmodulated power signal having a first frequency and a modulated interrogation signal having a second frequency being different from the first frequency, and receiving a modulated response signal having a third frequency, the third frequency being one of a harmonic and a subharmonic of the first frequency; and the above-described RFID tag. [0021 ] According to a further broad aspect, there is provided a method for operating a radio-frequency identification (RFID) tag, comprising: receiving an unmodulated power signal having a first frequency and a modulated interrogation signal having a second frequency being different from the first frequency; extracting interrogation information from the modulated interrogation signal; generating a modulated response signal having a third frequency based on tag data, the interrogation information and a first part of the unmodulated power signal, the third frequency being one of a harmonic and a subharmonic of the first frequency; converting a second part of the unmodulated power signal into a DC electrical signal for powering the RFID tag; and transmitting the modulated response signal via the at least one antenna, said receiving and said transmitting being performed via at least one antenna.

[0022] In one implementation, the method further comprises receiving a second modulated interrogation signal having the first frequency, and transmitting a second modulated response signal having the first frequency.

[0023] In one implementation, the method further comprises: extracting a second interrogation information from the second modulated interrogation signal; generating the second modulated response signal based on the tag data, the second interrogation information and a first part of the second modulated interrogation signal; transmitting the second modulated response signal via the at least one antenna; and converting a second part of the second modulated interrogation signal into a DC electrical signal to power the RFID tag.

[0024] Implementations of the present technology each have at least one of the above- mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein.

[0025] Additional and/or alternative features, aspects and advantages of implementations of the present technology will become apparent from the following description, the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0027] Fig. 1 schematically illustrates an RFID system comprising an RFID reader and an RFID tag, in accordance with an implementation;

[0028] Fig. 2 illustrates an RFID tag comprising a single antenna, in accordance with an implementation;

[0029] Fig. 3 illustrates an RFID tag comprising two antennas, in accordance with a first implementation;

[0030] Fig. 4 illustrates an RFID tag comprising two antennas, in accordance with a second implementation;

[00 1] Fig. 5 illustrates an RFID tag comprising two antennas, in accordance with a third implementation;

[0032] Fig. 6 illustrates an RFID tag comprising three antennas, in accordance with a fourth implementation;

[0033] Fig. 7 illustrates an RFID tag comprising three antennas, in accordance with a fifth implementation;

[0034] Fig. 8 illustrates an RFID tag comprising three antennas, in accordance with a sixth implementation;

[0035] Fig. 9 illustrates an RFID tag comprising three antennas, in accordance with a seventh implementation; and

[0036] FIG. 10 illustrates a flowchart of a method for operating a RFID tag, according to an implementation of the present disclosure. DETAILED DESCRIPTION

[0037] The examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the present technology and not to limit its scope to such specifically recited examples and conditions. It will be appreciated that those skilled in the art may devise various arrangements which, although not explicitly described or shown herein, nonetheless embody the principles of the present technology and are included within its spirit and scope.

[00 8] Furthermore, as an aid to understanding, the following description may describe relatively simplified implementations of the present technology. As persons skilled in the art would understand, various implementations of the present technology may be of a greater complexity.

[0039] In some cases, what are believed to be helpful examples of modifications to the present technology may also be set forth. This is done merely as an aid to understanding, and, again, not to define the scope or set forth the bounds of the present technology. These modifications are not an exhaustive list, and a person skilled in the art may make other modifications while nonetheless remaining within the scope of the present technology. Further, where no examples of modifications have been set forth, it should not be interpreted that no modifications are possible and/or that what is described is the sole manner of implementing that element of the present technology.

[0040] Fig. 1 illustrates one implementation of an RFID system 10. The RFID system 10 comprises an RFID reader 12 (hereinafter referred to as a reader) and at least one RFID tag 14 (Hereinafter referred to as a tag).

[0041] The RFID reader 12 is configured for generating and emitting a modulated interrogation signal and an unmodulated power signal, and receiving a modulated response signal from the tag 14. It should be understood that the modulated interrogation signal, the unmodulated power signal and the modulated response signal are radiofrequency (RF) signals. The modulated interrogation signal has a first frequency chosen in a first frequency band and is modulated so as to have information/data encoded therein. The unmodulated power signal is a continuous-wave (CW) RF signal and has a second frequency chosen in a second frequency band. The first and second frequency bands are distinct and do not overlap so that the first and second frequencies are different. The modulated response signal has a third frequency and is modulated so as to have information/data encoded therein. The third frequency is chosen to be a harmonic or subharmonic of the second frequency so that the modulated response signal is a harmonic or subharmonic signal of the unmodulated power signal.

[0042] The tag 14 is configured for receiving the modulated interrogation signal and the unmodulated power signal, and generating and emitting the modulated response signal. As described in greater detail below, a first portion of the received unmodulated power signal is used by the tag 14 for powering all of the components of the tag 14 and a second portion of the unmodulated power signal is used by the tag 14 for generating the modulated response signal.

[0043 ] The RFID reader 12 is connected to a power source (not shown) and comprises a signal processing unit 20, a storing unit or memory 22 and at least one antenna 24. Information about the RFID reader 12 and/or the tag 14 may be stored in the storing unit 22. The memory 22 can be used if the RFID reader 12 needs to keep track of tags locally, before transmitting the information to the users, for example. The signal processing unit 20 is configured for generating the modulated interrogation signal to be transmitted to the tag 14 and the unmodulated power signal. As known in the art, the modulated interrogation signal may be indicative of a command and/or a query. The modulated interrogation signal can be any mandatory, optional or proprietary commands, predicted in standard RFID protocols. The signal processing unit is further configured for emitting the modulated interrogation signal and the unmodulated power signal via the antenna 24.

[0044] In one implementation, the signal processing unit 20 is configured for generating and emitting the power signal substantially continuously independently of the emission for the modulation interrogation signal. In another implementation, the signal processing unit 20 is configured for substantially concurrently emitting the power signal and the modulated interrogation signal. For example, the emission of the power signal and the modulated interrogation signal may start and end concurrently. In another example, the emission of the power signal may start slightly prior to the emission of the modulated interrogations signal and/or ends slightly after the end of the emission of the modulated interrogation signal.

[0045] It should be understood that the number of antennas contained in the RFID reader 12 may vary as long as the RFID reader 12 contains at least one antenna. In one implementation, the RFID reader 12 comprises a single antenna so that the power signal and the modulated interrogation signal are emitted by the single antenna and the modulated response signal is also received by the single antenna. In another implementation, the RFID reader 12 comprises two antennas. In this case, one antenna is shared by two of the three signals while the other antenna is dedicated to only the other one of the three signals. For example, a first antenna may be dedicated to the transmission of the power and interrogation signals while the second antenna is dedicated to the reception of the response signal from the tag 14. In another example, the first antenna may be dedicated to the transmission of the interrogation signal and the reception of the response signal while the second antenna is dedicated to the transmission of the power signal only. In a further implementation, the RFID reader 12 comprises three different antennas. In this case, a first antenna is dedicated to the transmission of the power signal, a second antenna is dedicated to the transmission of the interrogation signal, and a third antenna is dedicated to the reception of the response signal.

[0046] In some implementations, the signal processing unit 20 is configured for varying the frequency of the power signal within the second frequency band. In some implementations, the frequency of the power signal varies within a set of predefined frequencies. In one implementation, the frequency of the power signal alternates between two predefined frequencies. Such an alternance between two predefined frequencies allows for the determination of the position of the tag 14, as known in the art.

[0047] In some implementations, the RFID reader 12 comprises a mono-static RFID reader. In other implementations, the RFID reader 12 comprises a bi-static RFID reader. [0048] The tag 14 comprises a signal processing unit 30, a storing unit or memory 32. and at least one antenna 34. Information such as tag ID, information on the product to which the tag 14 is associated with, information received from the RFID reader 12, etc. may be stored on the storing unit 32. The signal processing unit 30 is configured for extracting information from the received modulated interrogation signal, converting a first portion or part of the power signal into electrical power for powering the tag 14, generating the response signal based on the received interrogation signal using the second portion or part of the power signal and transmitting the response signal via the antenna 34. The response signal is generated by modulating the second portion of the received power signal to encode response information or data therein and changing the frequency of the second portion of the power signal to a harmonic or subharmonic of its initial frequency, i.e., to a harmonic or subharmonic of the received power signal.

[0049] In some implementations in which the modulated interrogation signal is indicative of a command, the tag 14 may generate no response signal. In other implementations in which the modulated interrogation signal is indicative of a command or a query, a signal response is generated based on the information extracted from the interrogation signal.

[0050] In some implementations, the signal processing unit 30 is configured for first modulating the second portion of the power signal, thereby obtaining a modulated signal, and then changing the frequency of the modulated signal. In other implementations, the signal processing unit 30 is configured for first changing the frequency of the second portion of the power signal, thereby obtaining a frequency-changed signal, and then modulating the frequency-changed signal.

[0051] In some implementations, the signal processing unit 30 comprises an alternating current (AC) to direct current (DC) converter such as a rectifier for converting the first portion of the power signal into an electrical power signal that is then used for powering the tag 14.

[0052] In some implementations, the signal processing unit 30 comprises a modulator for modulating the second portion of the power signal and a frequency-shifting component configured for changing the frequency of an RF signal to a harmonic or subharmonic frequency. For example, the frequency- shifting component may be a non-linear component that causes nonlinearity. In one implementation the non-linear component is a passive nonlinear component such as a diode or a rectifier.

[0053] In one implementation, the AC-to-DC conversion and the frequency shifting are performed by a single component such as a rectifier. In this case, the rectifier receives the unmodulated power signal from the antenna 34 and generates two signals, i.e. a DC power signal for powering the tag 14 and a unmodulated carrier signal of which the frequency is a harmonic or subharmonic of the frequency of the received unmodulated power signal. A first filter may be used for extracting the DC power signal from the output of the rectifier and a second filter may be used for extracting the unmodulated carrier signal from the output of the rectifier. The unmodulated carrier signal is then modulated to generate the modulated response signal.

[0054 ] It should be understood that the tag 14 further comprises a substate on which the different components constituting the tag 14 such as the signal processing unit 30, the antenna 34 and the memory 32 are mounted

[0055] In the following, there are described several different implementations for the above-described RFID tag 14.

[0056] Fig. 2 illustrates one implementation of an RFID tag 50 that comprises a single antenna 52. In addition to the antenna 52, the tag 50 comprises a processor or processing unit 54 such as a microprocessor, a memory 56, a demodulator 58, a rectifier 60, a modulator 62 and a non-linear component 64 such as a diode. The tag 50 further comprises a substrate 66 on which all of the other elements 52-64 are mounted.

[0057] The antenna 52 is configured for receiving a modulated interrogation signal having a first frequency and emitted by an RFID reader, and an unmodulated power signal having a second and different frequency and also emitted by the RFID reader.

[0058] The memory 56 is configured to store therein information or data such as an identification of the tag 50 and/or information received from the RFID reader, and the processing unit 54 is operatively connected to the memory 56 and configured for interpreting reader’s modulated signal, taking required actions and optionally generating response data (i.e., a response to the interrogation signal) based on information contained in the memory 56 such as the tag ID and interrogation data extracted from the modulated interrogation signal.

[0059] The demodulator 58 is operatively connected to the antenna 52 to receive the modulated interrogation signal therefrom and to the processing unit 54. The demodulator 58 is configured for extracting interrogation information or data from the modulated interrogation signal and transmit the extracted interrogation data to the processing unit 54.

[006 ] The input of the rectifier is operatively connected to the antenna 52 for receiving a first part of the unmodulated power signal therefrom and the output of the rectifier 60 is operatively connected to the processing unit 54, the memory 56, the demodulator 58 and the modulator 62 in order to power these components 54, 56, 58 and 62. The rectifier 60 is configured for converting the first portion of the unmodulated power signal into a DC power signal which is used to power the processing unit 54, the memory 56, the demodulator 58 and the modulator 62.

[0061 ] The modulator 62 receives the second part or portion of the unmodulated power signal and is operatively connected to the processing unit 54 for receiving the response data signal therefrom and modulating the second portion of the unmodulated power signal based on the received response data signal to generating a modulated signal having the same carrier frequency as that of the received unmodulated power signal. The non-linear component 64 is operatively connected to the modulator 62 for receiving the modulated signal therefrom. The non-linear component 64 is configured for changing the carrier frequency of the modulated signal received from the modulator 62 to a harmonic or subharmonic frequency, thereby obtaining the modulated response signal in which a response to the interrogation is encoded. The modulated response signal then propagates upon to the antenna 52 for emission therefrom.

[0062] In another implementation, the non-linear component 64 is configured for receiving the second portion of the received unmodulated power signal and changing the frequency of this signal to a harmonic or subharmonic frequency, thereby obtaining a frequency shifted signal. The modulator 62 is operatively connected to the non-linear component 64 to receive the frequency-shifted signal therefrom and to the processing unit 54 to receive the response data signal therefrom. The modulator 62 is configured for modulating the frequency-shifted signal based on the received response data signal to generate the modulated response signal which is propagated up to the antenna 52 for broadcasting.

[0063] It should be understood that the tag 50 may further comprise components such as circulators, diplexers, and/or the like (not shown) to split and/or direct signals.

[0064] While the tag 52 comprises a single antenna the implementations illustrated in Figs. 3-5 comprise two antennas. When a tag comprises two antennas, a first antenna is dedicated to two of three signals (i.e., the modulated interrogation signal, the unmodulated power signal and the modulated response signal) while the second antenna is dedicated to a single one of the three signals.

[0065] Fig. 3 illustrates an RFID tag 70 which comprises a first antenna 72 and a second antenna 74 which are mounted on the substrate 66. The remaining components of the tag 70 are the same as those comprised in the tag 50. The antenna 72 is dedicated to the reception of the modulated interrogation signal and the emission of the modulated response signal while the antenna 74 is dedicated to the reception of the unmodulated power signal. The antenna 72 is operatively connected to the demodulator 58 and the non-linear component 64. The antenna 74 is operatively connected to the rectifier 60 and the modulator 62. As a result, the modulated interrogation signal is received by the antenna 72 and propagates up to the demodulator 58 while the unmodulated power signal is received by the antenna 74 and is split into a first portion which propagates up to the rectifier 60 and a second portion which propagates up to the modulator 62. The modulated response signal outputted by the non-linear component 64 propagates up to the antenna 72 for emission therefrom. It should be understood that the remaining of the tag 70 operates similarly to the tag 50. [0066] Fig. 4 illustrates an RFID tag 80 which comprises a first antenna 82 and a second antenna 84 which are both mounted on the substrate 66. The remaining components of the tag 80 are the same as those comprised in the tag 50. The antenna 82 is dedicated to the reception of the modulated interrogation signal while the antenna 84 is dedicated to the reception of the unmodulated power signal and the emission of the modulated response signal. The antenna 82 is operatively connected to the demodulator 58. The antenna 84 is operatively connected to the rectifier 60 and the modulator 62. As a result, the modulated interrogation signal is received by the antenna 82 and propagates up to the demodulator 58. The unmodulated power signal is also received by the antenna 72 and split into a first portion that propagates up to the rectifier 60 and a second portion that propagates up to modulator 62. The modulated response signal outputted by the non-linear component 64 propagates up to the antenna 84 for emission therefrom. It should be understood that the remaining of the tag 80 operates similarly to the tag 50.

[0067] Fig. 5 illustrates an RFID tag 90 which comprises a first antenna 92 and a second antenna 94 which are mounted on the substrate 66. The remaining components of the tag 90 are the same as those comprised in the tag 50. The antenna 92 is dedicated to the reception of the modulated interrogation signal and the reception of the unmodulated power signal while the antenna 94 is dedicated to the emission of the modulated response signal. The antenna 92 is operatively connected to the demodulator 58, the rectifier 60 and the modulator 62. The antenna 94 is operatively connected to the non-linear component 64. As a result, the modulated interrogation signal is received by the antenna 92 and propagates up to the demodulator 58 while the unmodulated power signal is also received by the antenna 92 and is split into a first portion which propagates up to the rectifier 60 and a second portion which propagates up to the modulator 62. The modulated response signal outputted by the non-linear component 64 propagates up to the antenna 94 for emission therefrom. It should be understood that the remaining of the tag 90 operates similarly to the tag 50.

[0068] Fig. 6 illustrates one implementation of an RFID tag 100 which comprises a first antenna 102, a second antenna 104 and a third antenna 106. The remaining components of the tag 100 are the same as those comprised in the tag 50. The antenna 102 is dedicated to the reception of the modulated interrogation signal, the antenna 104 is dedicated to the reception of the unmodulated power signal and the antenna 106 is dedicated to the emission of the modulated response signal. The antenna 102 is operatively connected to the demodulator 58. The antenna 104 is operatively connected to the rectifier 60 and the modulator 62. The antenna 106 is operatively connected to the non-linear component 64. As a result, the modulated interrogation signal is received by the antenna 102 and propagates up to the demodulator 58. The unmodulated power signal is received by the antenna 104 and is split into a first portion which propagates up to the rectifier 60 and a second portion which propagates up to the modulator 62. The modulated response signal outputted by the non-linear component 64 propagates up to the antenna 106 for emission therefrom. It should be understood that the remaining of the tag 100 operates similarly to the tag 50.

[0069] It is to be noted that, in some implementations, the various RFID tags illustrated in Figs. 2-6 may further be adapted to be operative with different RFID readers, as described below. Figs. 7-9 illustrate various implementations of RFID tags configured to further be operative with different RFID readers.

[0070] In one implementation, a first RFID reader (not illustrated) is configured to transmit two signals and receive a third signal. The first transmitted signal is the unmodulated power signal having a first frequency. The second transmitted signal is the modulated interrogation signal having the second frequency being different from the first frequency. The received signal is the modulated response signal generated by the RFID tag having a third frequency being one of a harmonic and a subharmonic of the first frequency. Without limiting the scope of the present disclosure, the first frequency may be around 915 MHz and the second frequency may be around 2.4 GHz.

[0071] In another implementation, a second RFID reader (not illustrated) is configured to transmit a first signal and receive a second signal. In this implementation, the first transmitted signal is the modulated interrogation signal which is a sequence of unmodulated portions and modulated portions. The modulated interrogation signal has the first frequency (for example 915 MHz). The received signal is the modulated response signal generated by the RFID tag having the same frequency as that of the first transmitted signal.

[0072] The RFID tags illustrated in Figs. 7-9 can be operated with the first RFID reader as well as with the second RFID reader. When operated with the first RFID reader, the RFID tag generates the modulated response signal having a third frequency being one of a harmonic and a subharmonic of the first frequency. When operated with the second RFID reader, the RFID generates the modulated response signal generated by the RFID tag having the same frequency as that of the first transmitted signal

[0073] Fig. 7 illustrates one implementation of an RFID tag 110 which comprises a second demodulator 108. The remaining components of the tag 110 are the same as those comprised in the tag 100. The demodulator 108 is operatively connected to the antenna 104 to receive the modulated interrogation signal having a first frequency therefrom and to the processing unit 54. The demodulator 108 is configured for extracting the interrogation information or data from the modulated interrogation signal and transmit the extracted interrogation data to the processing unit 54. The processing unit 54 is configured to generate a response data signal based on the interrogation information. In some implementations, the demodulator 108 may be different from the demodulator 58 in a manner that the demodulator 108 may be configured to be operative at the first frequency and the demodulator 58 may be configured to be operative at the second frequency.

[0074] The antenna 104 is further operatively connected to the rectifier 60 and the combination of the modulator 62 and the non-linear component 64. As a result, the modulated interrogation signal is received by the antenna 104 propagates towards the rectifier 60 and the combination of the modulator 62 and the non-linear component 64.

[0075] The input of the rectifier 60 is operatively connected to the antenna 104 for receiving the modulated interrogation signal therefrom and the output of the rectifier 60 is operatively connected to the processing unit 54, the memory 56, the demodulator 108 and the modulator 62 in order to power these components. The rectifier 60 is configured for converting at least a portion of the modulated interrogation signal into a DC power signal which is used to power the processing unit 54, the memory 56, the demodulator 108 and the modulator 62.

[0076] The combination of the modulator 62 and the non-linear component 64 is configured to provide a frequency shift and modulation to the modulated interrogation signal based on the response data signal received from the processing unit 54. The combination of the modulator 62 and the non-linear component 64 generates a modulated response signal. It is to be noted that not all of the modulated interrogation signal is frequency shifted by the non-linear component 64. As a result, at least a portion or a component of the modulated interrogation signal is modulated at the first frequency. The modulated response signal then propagates upon to the antennas 104 and 106 for emission therefrom. In doing so, at least portion or the component of the modulated response signal which is modulated at the first frequency is transmitted by the antenna 104 and is detected by the RFID reader which is configured to detect signal at the first frequency. It should be understood that the remaining of the tag 110 operates similarly to the tag 100.

[0077] When the RFID tag 110 is operated with the first RFID reader, the antenna 102 receives the modulated interrogation signal at the second frequency, the antenna 104 receives the unmodulated power signal at the first frequency and the remaining of the tag 110 operates similarly to the tag 100, as described above.

[0078] When the RFID tag 110 is operated with the second RFID reader, the antenna 104 is dedicated to the reception of a modulated interrogation signal having the first frequency. The modulated interrogation signal is generated by the second RFID reader at the first frequency. The modulated interrogation signal includes a sequence of signal portions that include at least a first signal portion or part and a second signal portion or part. The first signal part is unmodulated and corresponds to a DC signal while the second signal part is modulated and comprises interrogation information encoded therein. The antenna 104 is dedicated to the emission of a modulated response signal of which a component is at the first frequency so as to be detected by the second RFID reader that emitted the interrogation signal at the first frequency. The modulated response signal is generated by the RFID tag 110 in response to the modulated interrogation signal. [0079] Fig. 8 illustrates one implementation of an RFID tag 120. The components of the tag 120 are the same as those comprised in the tag 110 with a difference that the antenna 102 is further operatively coupled to the rectifier 60 and the combination of the modulator 62 and the non-linear component 64.

[0080] When the RFID tag 120 is operated with the first RFID reader (which corresponds to a first operation mode for the tag 120), the antenna 102 receives the modulated interrogation signal having the first frequency, the antenna 104 receives the unmodulated power signal having the second frequency and the remaining of the tag 130 operates similarly to the tag 100.

[0081] When the RFID tag 120 is operated with the second RFID reader (which corresponds to a second operation mode for the tag 120), the input of the rectifier 60 is operatively connected to the antenna 102 for receiving the modulated interrogation signal having the first frequency therefrom, and to the output of the rectifier 60 is operatively connected to the processing unit 54, the memory 56, the demodulator 58 and the modulator 62 in order to power these components 54, 56, 58 and 62. The rectifier 60 is configured for converting at least a portion of the modulated interrogation signal into a DC power signal which is used to power the processing unit 54, the memory 56, the demodulator 58 and the modulator 62.

[0082] Further, the combination of the modulator 62 and the non-linear component 64 generates the modulated response signal that then propagates upon to the antenna 106 for emission therefrom. At least a portion of the modulated response signal is modulated at the first frequency. In doing so, the at least portion or the component of the modulated response signal which is modulated at the first frequency is transmitted by the antenna 102 and is detected by the second RFID reader which is configured to detect signal at the first frequency. It should be understood that the remaining of the tag 120 operates similarly to the tag 110.

[0083] Fig. 9 illustrates one implementation of an RFID tag 130 which comprises a second rectifier 112. The remaining components and connections of the tag 130 are the same as those comprised in the tag 120. The rectifier 112 is operatively connected to the antenna 102 to receive the modulated interrogation signal having the first frequency therefrom. The output of the rectifier 112 is operatively connected to the processing unit 54, the memory 56, the demodulator 58 and the modulator 62 in order to power these components 54, 56, 58 and 62. The rectifier 60 is configured for converting at least a portion of the modulated interrogation signal into a DC power signal which is used to power the processing unit 54, the memory 56, the demodulator 58 and the modulator 62. In some implementations, the rectifier 112 may be different from the rectifier 60 in a manner that the rectifier 60 may be configured to be operative at the first frequency and the rectifier 112 may be configured to be operative at the second frequency.

[0084] When the RFID tag 130 is operated with the first RFID reader, the antenna 102 receives the modulated interrogation signal having the second frequency, the antenna 104 receives the unmodulated power signal having the first frequency and the remaining of the tag 130 operates similarly to the tag 100.

[0085] When the RFID tag 130 is operated with the second RFID reader, the antenna 102 receives the modulated interrogation signal having the first frequency. Similar to the RFID tag 110, the modulated interrogation signal is used to power various components of the RFID tag 130.

[0086 ] Further, the combination of the modulator 62 and the non-linear component 64 generates the modulated response signal that then propagates upon to the antennas 102 and 106 for emission therefrom. At least a portion of the modulated response signal is modulated at the first frequency. In doing so, the at least portion or the component of the modulated response signal which is modulated at the first frequency is transmitted by the antenna 102 and is detected by the second RFID reader which is configured to detect signal at the first frequency. It should be understood that the remaining of the tag 130 operates similarly to the tag 110.

[0087] Referring to Figs. 2-9, it should also be understood that the positions of the modulator 62 and the non-linear component 64 can be reversed so that the non-linear component 64 receives the second portion of the unmodulated power signal. [0088] Similar to the RFID tag, the number of antennas contained in the RFID reader may vary as long as the RFID reader comprises at least one antenna. For example, the RFID reader may be provided with a single antenna, two antennas or three antennas for emitting the modulated interrogation signal and the unmodulated power signal and receiving the modulated response signal.

[0089] In some implementations, the above-described RFID tag may receive high- power unmodulated signals while transmitting and receiving low-power modulated signals. Modulated and unmodulated signals are at different frequencies as described above. The reader-to-tag low-power modulated signal is used to send interrogation data to the tag. This data transfer is necessary to establish a handshake between the tag and the reader. The high- power unmodulated signal is used as a power signal for powering up the tag and as a carrier signal for the tag's response.

[0090] In some implementations, the present RFID system provides a practical solution for ultra-long range and high read-yield passive RFID systems. The use of an unmodulated power signal in conjunction with modulated signals allows resolving the inherent inefficiency of harmonic tags and improve signal -to-interference and noise ratio.

[0091] FIG. 10 illustrates a flowchart of a method 200 for operating a RFID tag, according to various implementations of the present disclosure. As shown, the method 200 commences at step 202, where the RFID tag 50 receive an unmodulated power signal having a first frequency and a modulated interrogation signal having a second frequency being different from the first frequency.

[0092] The method proceeds at step 204, where the RFID tag 50 extracts interrogation information from the modulated interrogation signal.

[0093 ] The method proceeds to step 206, where the RFID tag 50 generates a modulated response signal having a third frequency based on tag data, the interrogation information and a first part of the unmodulated power signal, the third frequency being one of a harmonic and a subharmonic of the first frequency. [0094] The method proceeds to step 208, where the RFID tag 50 converts a second part of the unmodulated power signal into a DC electrical signal for powering the RFID tag.

[0095] Finally, at step 210, the RFID tag 50 transmits the modulated response signal via at least one antenna, said receiving and said transmitting being performed via at least one antenna.

[0096] Modifications and improvements to the above-described implementations of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting.

Claims

What is claimed is:

1. A radio-frequency identification (RFID) tag comprising: a substrate; at least one antenna for receiving an unmodulated power signal having a first frequency and a modulated interrogation signal having a second frequency being different from the first frequency, and transmitting a modulated response signal having a third frequency, the third frequency being one of a harmonic and a subharmonic of the first frequency; a storing unit for storing tag data; and a signal processing unit for: extracting interrogation information from the modulated interrogation signal; generating the modulated response signal based on the tag data, the interrogation information and a first part of the unmodulated power signal; transmitting the modulated response signal via the at least one antenna; and converting a second part of the unmodulated power signal into a DC electrical signal for powering the RFID tag; wherein the at least one antenna, the signal processing unit and the storing unit are mounted to the substrate.

2. The RFID tag of claim 1, wherein the signal processing unit comprises: a demodulator for extracting the interrogation information from the modulated interrogation signal; an AC-to-DC converter for converting the second part of the unmodulated power signal into a DC electrical signal; a processor for receiving the interrogation information and generating a response data signal based on the tag data and the interrogation information; and a modulator and a frequency-shifting component for modulating the first part of the unmodulated power signal according to the response data signal and converting the first 5 frequency to the third frequency.

3. The RFID tag of claim 2, wherein the modulator is configured for receiving and modulating the first part of the unmodulated power signal according to the response data signal to obtain a modulated carrier signal and the frequency- shifting component is configured for changing the first frequency of the modulated carrier signal to the third frequency to obtain

10 the modulated response signal.

4. The RFID tag of claim 2, wherein the frequency-shifting component is configured for receiving the first part of the unmodulated power signal and changing the first frequency of the first part of the unmodulated power signal to the third frequency to obtain a frequency- shifted signal, and the modulator is configured for modulating the frequency-

15 shifted signal according to the response data signal to obtain the modulated response signal.

5. The RFID tag of any one of claims 2 to 4, wherein the AC-to-DC converter comprises a first rectifier.

6. The RFID tag of any one of claims 2 to 5, wherein the frequency- shifting component comprises non-linear component.

207. The RFID tag of claim 6, wherein the non-linear component comprises one of a diode and a second rectifier.

8. The RFID tag of claim 1, wherein the signal processing unit comprises: a demodulator for extracting the interrogation information from the modulated interrogation signal; a rectifier for converting the second part of the unmodulated power signal into a DC electrical signal and changing the first frequency of the first part of the unmodulated power signal to the third frequency to obtain a frequency-shifted signal; a processor for receiving the interrogation information and generating a response data 5 signal based on the tag data and the interrogation information; and a modulator for modulating the frequency-shifted signal according to the response data signal to obtain the modulated response signal.

9. The RFID tag of any one of claims 1 to 8, wherein the at least one antenna comprises one of a single antenna, two antennas and three antennas.

1010. The RFID tag of claim 1, wherein the at least one antenna further receives a second modulated interrogation signal having the first frequency, and transmits a second modulated response signal having the first frequency.

11. The RFID tag of claim 10, wherein the signal processing unit further: extracts a second interrogation information from the second modulated interrogation 15 signal; generates the second modulated response signal based on the tag data, the second interrogation information and a first part of the second modulated interrogation signal; transmits the second modulated response signal via the at least one antenna; and converts a second part of the second modulated interrogation signal into a DC electrical 20 signal to power the RFID tag.

12. The RFID tag of claim 11, wherein the signal processing unit comprises: a demodulator for extracting the second interrogation information from the second modulated interrogation signal; a rectifier for converting the second part of the second modulated interrogation signal into the DC electrical signal; a processor for receiving the second interrogation information and generating a response data signal based on the tag data and the interrogation information; and

5 a modulator for modulating the second modulated interrogation signal according to the response data signal to obtain the second modulated response signal.

13. A radio-frequency identification (RFID) system comprising: a reader comprising at least one antenna, a signal processing unit and a storing unit, the processing unit being configured for generating an unmodulated power signal having a first 10 frequency and a modulated interrogation signal having a second frequency being different from the first frequency, and receiving a modulated response signal having a third frequency, the third frequency being one of a harmonic and a subharmonic of the first frequency; and the RFID tag of any one of claims 1 to 12.

1514. A method for operating a radio-frequency identification (RFID) tag, comprising: receiving an unmodulated power signal having a first frequency and a modulated interrogation signal having a second frequency being different from the first frequency; extracting interrogation information from the modulated interrogation signal; generating a modulated response signal having a third frequency based on tag data, the 20 interrogation information and a first part of the unmodulated power signal, the third frequency being one of a harmonic and a subharmonic of the first frequency; converting a second part of the unmodulated power signal into a DC electrical signal for powering the RFID tag; and transmitting the modulated response signal via at least one antenna, said receiving and said 25 transmitting being performed via the at least one antenna.

15. The method of claim 14, further comprises receiving a second modulated interrogation signal having the first frequency, and transmitting a second modulated response signal having the first frequency.

16. The method of claim 15, further comprises: extracting a second interrogation information from the second modulated interrogation signal; generating the second modulated response signal based on the tag data, the second interrogation information and a first part of the second modulated interrogation signal; transmitting the second modulated response signal via the at least one antenna; and converting a second part of the second modulated interrogation signal into a DC electrical signal to power the RFID tag.