RFID tag positioning based on mobile phone

Abstract

An apparatus includes a passive RFID tag and a backscatter module. A portion of an identification signal generated by the RFID tag in response to an RF signal transmitted by an RFID reader is received by the backscatter module. The backscatter module is to generate a voltage output related to a power level of the portion of the identification signal. And the backscattering module controls the reflectivity of the antenna by using the voltage output and enables the antenna to backscatter a signal in a frequency band related to the voltage output so as to position the RFID tag.

Description

Technical Field

[0001] The disclosed embodiments generally relate to Radio Frequency Identification (RFID) tag positioning, and more specifically, to RFID tag positioning based on mobile phones. Background Technology

[0002] RFID tag-based object location is a popular and effective method for precisely locating and tracking objects across a variety of applications. By utilizing tags, typically small electronic devices equipped with wireless communication capabilities, objects can be accurately identified and their location determined in real time. This technology is widely used in asset tracking, supply chain management, indoor navigation, and many other fields where knowing the precise location of objects is crucial.

[0003] Tag-based object localization typically involves attaching or embedding tags to objects of interest. The signals emitted by these tags can be detected and interpreted by receivers or readers strategically placed in the environment. By measuring signal strength or utilizing other localization techniques, such as time-of-flight or trilateration, the location of the tagged object can be determined with high accuracy.

[0004] While tag-based object localization offers many advantages, it also has drawbacks. Especially when using multiple tags on a large scale, the implementation cost can be substantial. Depending on the tag type, batteries may need to be replaced periodically, incurring maintenance costs and requiring careful consideration of power management strategies.

[0005] Therefore, there is a need for an improved apparatus and method for RFID tag positioning. Consequently, it is desirable to provide an apparatus and method that solves at least some of the aforementioned problems. Summary of the Invention

[0006] The disclosed embodiments relate to an apparatus and method for RFID tag positioning. Specifically, the disclosed embodiments relate to using a mobile communication device to locate passive RFID tags.

[0007] According to the first aspect, the above and other implementations and advantages are obtained through an apparatus. In one embodiment, the apparatus includes a passive RFID tag and a backscattering module. A portion of the identification signal generated by the RFID tag is received by the backscattering module. The backscattering module is used to generate a voltage output related to the power level of said portion of the identification signal. The voltage output is used to control the reflectivity of an antenna. In one embodiment, an antenna may be coupled to the backscattering module. The antenna is used to backscatter the signal in a frequency band related to the voltage output for RFID tag positioning. Aspects of the disclosed embodiments achieve accurate positioning of passive RFID tags.

[0008] In one possible implementation, the backscattering module includes an envelope detector, a switching device, and a broadband antenna. In one embodiment, the switching device includes a field-effect transistor (FET) device. The portion of the identification signal is the input to the envelope detector, which generates a voltage output related to the power level of the portion of the identification signal. The voltage output is used to switch the FET transistor between an on and off state. The voltage at the gate of the FET is used to control the reflectivity of the antenna. The antenna is used to backscatter signals within its frequency band based on the control voltage. Aspects of the disclosed embodiments achieve precise positioning of passive RFID tags.

[0009] In one possible implementation, the RFID reader is a mobile communication device or is included within a mobile communication device. Using a mobile communication device for tag localization reduces the need for RFID reader sites and improves localization accuracy because the signal-to-noise ratio (SNR) increases as the mobile communication device moves toward the target. Existing characteristics of mobile communication devices can be used to improve path estimation and tag localization.

[0010] In one possible implementation, the mobile communication device is used to receive and record channel state information (CSI) of an ambient signal transmitted using a wireless communication protocol; detect a scattered signal from a backscattering module corresponding to the ambient signal; and estimate the distance of the RFID tag by comparing the difference between the scattered signal and the corresponding CSI of the ambient signal. Aspects of the disclosed embodiments enable the transmission of CW signals in one frequency band and the simultaneous reception of scattered signals in multiple frequency bands, thereby providing multi-band operation. This reduces multipath interference in single-frequency operation and achieves better distance estimation through multi-band CSI.

[0011] In one possible implementation, the mobile communication device controls the reflectivity of the antenna to enable and disable the transmission of the scattered signal. The α_code is known to the mobile communication device, and the scattering path can be enabled and disabled by turning the CW signal on and off. This only leaves the delay τ as an unknown to be estimated. The delay for each RFID tag and each frequency band can be estimated independently. Average delay estimation can improve the accuracy of distance estimation.

[0012] In one possible implementation, the mobile communication device is configured to transmit RF signals to one or more RFID tags on a first frequency band and receive scattered signals from one or more of the RFID tags on multiple frequency bands. The multi-band scattering method of the disclosed embodiments is capable of transmitting CW signals on one frequency band and simultaneously receiving signals on multiple frequency bands.

[0013] In one possible implementation, the movement path of the mobile communication device can be identified, and the distance from the RFID tag to the mobile device can be calculated along the movement path at different locations. The RFID tag can then be located based on the distances calculated at different locations. By weighting the combined distance estimates at different locations, the tag's position can be located with enhanced accuracy.

[0014] According to the second aspect, the above and other implementations and advantages are obtained through an RFID tag positioning system. In one embodiment, the system includes an RFID reader, a passive RFID tag, and a backscattering module. A portion of the identification signal generated by the RFID tag in response to an RF signal sent by the RFID reader is received by the backscattering module. The backscattering module is used to generate a voltage output related to the power level of said portion of the identification signal. The voltage output is used to control the reflectivity of an antenna coupled to the backscattering module. The antenna is used to backscatter the signal within a frequency band related to the voltage output for RFID tag positioning. The aspects of the disclosed embodiments achieve accurate positioning of passive RFID tags.

[0015] In one possible implementation, the mobile communication device is used to receive and record channel state information of an environmental signal transmitted from the mobile communication device using a wireless communication protocol; detect a scattered signal from the backscattering module corresponding to the environmental signal; and estimate the distance of the RFID tag by comparing the difference between the channel state information corresponding to the scattered signal and the environmental signal. Various aspects of the disclosed embodiments achieve precise positioning of passive RFID tags.

[0016] In one possible implementation, the mobile communication device is used to control the reflectivity of the antenna to enable and disable the transmission of the scattered signal. Aspects of the disclosed embodiments achieve precise positioning of passive RFID tags.

[0017] In one possible implementation, the mobile communication device is used to transmit the RF signal on a first frequency band and receive scattered signals from one or more RFID tags on multiple frequency bands. This reduces multipath interference in single-frequency operation and achieves better distance estimation through multi-band CSI.

[0018] In one possible implementation, the mobile communication device is further configured to identify the movement path of the mobile communication device; calculate the distance from the RFID tag to the mobile communication device at different locations along the movement path; and locate the RFID tag based on the distances calculated at the different locations. Various aspects of the disclosed embodiments can enhance tag positioning accuracy.

[0019] According to a third aspect, the above and other implementations and advantages are achieved through a method. In one embodiment, the method includes: receiving a portion of an identification signal generated by an RFID tag; generating a voltage output related to the power level of the portion of the identification signal; using the output voltage to control the reflectivity of an antenna; causing the antenna to backscatter the signal in a frequency band related to the voltage output; and locating the RFID tag based on the backscattered signal. Aspects of the disclosed embodiments achieve precise positioning of passive RFID tags.

[0020] In one possible implementation, the method further includes: receiving and recording channel state information of an environmental signal transmitted from a mobile communication device using a wireless communication protocol; detecting a scattered signal from a backscattering module corresponding to the environmental signal; and estimating the distance of the RFID tag by comparing the difference between the channel state information corresponding to the scattered signal and the environmental signal. Various aspects of the disclosed embodiments provide better distance estimation through multi-band CSI.

[0021] In one possible implementation, the method further includes the mobile communication device transmitting the RF signal on a first frequency band and receiving scattered signals from one or more RFID tags on multiple frequency bands. Aspects of the disclosed embodiments enable the transmission of CW signals on one frequency band and the simultaneous reception of scattered signals on multiple frequency bands, thereby providing multi-band operation. This reduces multipath interference in single-frequency operation and achieves better distance estimation through multi-band CSI.

[0022] In one possible implementation, the method further includes: identifying the movement path of the mobile communication device; calculating the distance from the RFID tag to the mobile communication device at different locations along the movement path; and locating the RFID tag based on the distances calculated at the different locations. Aspects of the disclosed embodiments enable the use of existing features of mobile devices to improve movement path estimation and localization.

[0023] These and other aspects, implementations, and advantages of the exemplary embodiments will become apparent from the embodiments described herein in conjunction with the accompanying drawings. However, it should be understood that such description and drawings are for illustrative purposes only and should not be construed as limiting the invention; any limitation on the invention should be referenced to the appended claims. Additional aspects and advantages of the invention will be set forth in the following description, and some aspects and advantages will be apparent from the description or may be learned by practicing the invention. Furthermore, aspects and advantages of the invention may be realized and obtained by means or combinations particularly pointed out in the appended claims. Attached Figure Description

[0024] In the following detailed sections of this disclosure, aspects of the disclosed embodiments will be explained in more detail with reference to exemplary embodiments shown in the accompanying drawings, wherein like references denote like elements, and:

[0025] Figure 1 A block diagram of an exemplary system incorporating aspects of the disclosed embodiments is shown;

[0026] Figure 2 A block diagram of an exemplary system incorporating aspects of the disclosed embodiments is shown;

[0027] Figure 3 A schematic circuit diagram of an exemplary backscattering module incorporating aspects of the disclosed embodiments is shown;

[0028] Figure 4 A block diagram of an exemplary system incorporating aspects of the disclosed embodiments is shown;

[0029] Figure 5 Timing diagrams of broadband positioning according to various aspects of the disclosed embodiments are shown;

[0030] Figure 6 Distance estimations according to various aspects of the disclosed embodiments are shown;

[0031] Figure 7 Distance estimation of a mobile device according to various aspects of the disclosed embodiments is illustrated;

[0032] Figure 8 A flowchart illustrating the processing flow of various aspects according to the disclosed embodiments is shown. Detailed Implementation

[0033] Figure 1 A block diagram of an exemplary system 100 configured for mobile phone-based RFID tag location is shown. Aspects of the disclosed embodiments are directed to the accurate location of battery-free, passive RFID tags. When the RFID tag is passive, it does not emit sound or vibration like an active tag. This may require higher positioning accuracy and user interaction to help the user find the tag.

[0034] like Figure 1 As shown in the example, RFID reader 102 is used to transmit a continuous wave (CW) signal 110. In one embodiment, device 150 including RFID tag or chipset 106 is used to receive signal 110 and generate identification signal 112. In one embodiment, a portion 114 of the identification signal 112 generated by RFID tag 106 is received by backscatter module 108.

[0035] Also refer to Figure 2 In one embodiment, the backscattering module 108 is used to generate a voltage output 132 related to the power level of a portion 114 of the identification signal 112. The voltage output 132 is used to control the reflectivity of the antenna 138 coupled to the backscattering module 108 and enable the antenna 138 to backscatter the signal within the frequency band associated with the voltage output 132 for the location of the RFID tag 106.

[0036] At low frequencies, coverage and power transfer efficiency are high, but server multipathing limits positioning accuracy. The disclosed embodiments are designed for multi-frequency operating tags, which can mitigate problems associated with single-frequency designs.

[0037] like Figure 2 As shown, in one embodiment, the RFID chipset 106 in this example includes an antenna 104, a matching network or circuitry 120, an RF energy harvesting module or device 122, a microcontroller unit (MCU) or device 124, and a modulator block or device 128. In an alternative embodiment, the RFID chipset 106 may include any suitable components for passive and battery-free RFID tags.

[0038] In operation, the RFID reader 102 is used to send or transmit a continuous wave (CW) signal 110. In one embodiment, the continuous wave signal 110 may include a signal of approximately 918 MHz. In an alternative embodiment, the CW signal 110 sent by the RFID reader 102 may include any suitable signal, rather than a 918 MHz signal.

[0039] Signal 110 is received by antenna 104. Matching network 120 is used to pass signal 110 to energy harvesting block 122. Energy harvesting block 122 is used to store energy from signal 110 and power microcontroller unit 124.

[0040] The microcontroller unit 124 is used to transmit the RFID identification code 126. In one embodiment, the RFID identification code 126 is a binary code. In an alternative embodiment, the RFID code 126 is any suitable code. The microcontroller unit 124 can be used to repeatedly transmit the RFID identification code 126.

[0041] In one embodiment, the RFID identification code 126 is up-converted to 918 MHz by modulator 128 and transmitted as signal 112 by matching network 120 and antenna 104. For example, as Figure 4 As shown, signal 112 may include an on-off keying (OOK) signal or an amplitude shift keying (ASK) signal. Typically, the transmission of signal 112 is in the same frequency band as the transmission of signal 110 from RFID reader 102.

[0042] Backscattering circuitry or module 108 is typically used to extend the transmission of identification code 126 to broadband. For example... Figure 2 As illustrated in the example, in one embodiment, the backscattering circuit 108 includes an envelope detector 130, a voltage gain circuit 134, and a broadband antenna 138. In one embodiment, the voltage gain circuit 134 includes a field-effect transistor (FET) device. In an alternative embodiment, the voltage gain circuit 134 may include any suitable voltage gain device, rather than a field-effect transistor device.

[0043] Envelope detector 130 is typically used to couple a portion 114 of signal 112 from RFID chipset 106 and generate a voltage output 132 related to the power level of signal 112. The voltage output or signal 132 typically includes an RFID code 126 transmitted from MCU 124.

[0044] In one embodiment, the voltage generated by the envelope detector 130 is used to switch the voltage gain circuit or FET 134. Typically, FET 134 is turned on with a high-voltage input that connects antenna 138 to ground, where signals will be absorbed. When the input to FET 134 is a low-voltage input, FET 134 is either off or turned off, also known as an open-circuit state. In this case, the signal from antenna 138 will be totally reflected. The voltage presented at the gate of FET 134 controls the reflectivity of antenna 138. Antenna 138 backscatters signals within its frequency band associated with the control voltage for the purpose of locating RFID tag 106.

[0045] Figure 3 A schematic diagram of an exemplary backscattering circuit 300 is shown. In this example, input 302 is coupled from... Figure 2 The output 112 of the RFID chipset 106 is portion 114. Input 302 connects coupling capacitor C1 to diode D1. Transmission line TL is... Figure 1 and Figure 2 The 918 MHz signal is 110 quarter wavelengths. Resistor R1 and capacitor C2 act as a low-pass filter. The combination of diode D1, resistor R1, capacitor C2, and transmission line TL together serves as... Figure 2 The envelope detector 130 converts the ASK or OOK signal into a voltage output.

[0046] In this example, Q1 is a FET transistor that is turned on under a positive gate voltage and turned off under a negative gate voltage. When the FET transistor Q1 is on, the patch antenna 304 is used to receive signals within a distance of 2-6 GHz. The received signal is conducted to ground through FET Q1 and absorbed. When FET Q1 is disconnected or in an open state, the patch antenna 304 will be totally reflected.

[0047] Figure 4 An exemplary schematic block diagram of a system 400 incorporating aspects of the disclosed embodiments is shown. In this example, system 400 uses a mobile communication device or mobile phone 402 for RFID tag location. The use of mobile communication device 402 reduces the need for RFID reader sites and improves location accuracy because the signal-to-noise ratio increases as the mobile device 402 moves closer to the target RFID tag 106.

[0048] In one embodiment, mobile communication device 402 may include a mobile phone. Although the term generally refers to a mobile communication device or telephone, the aspects of the disclosed embodiments are not limited thereto. In alternative embodiments, mobile communication device 402 may include any suitable portable device with wireless connectivity, including, for example, virtual reality (VR) goggles and smart wearable devices.

[0049] In this example, the RFID chipset 106 is enabled by receiving a continuous wave (CW) signal 412 from the mobile device 402. The CW signal 412 transmits energy to all RFID tags 106 within a predetermined area. Although aspects of the disclosed embodiments are generally described herein with respect to a single RFID tag or chipset 106, the aspects of the disclosed embodiments are not limited thereto. In alternative embodiments, aspects of the disclosed embodiments can be implemented with any suitable number of RFID tags.

[0050] The powered RFID tag 106 will respond with identification code 414. Typically, identification code 414 is transmitted back to the mobile device 402 as a repeated ASK or OOK transmission.

[0051] During this process, the mobile device 402 is used to identify the number of RFID tags 106 in the vicinity or a predetermined area and their corresponding identification codes. Figure 5 An exemplary timing diagram 500 of a broadband positioning protocol according to various aspects of the disclosed embodiments is shown.

[0052] refer to Figure 4 and Figure 5 In one embodiment, the RFID tag 106 is controlled by a mobile device 402 that transmits a CW signal 412. The RFID tag 106 is used to disperse and / or transmit an identification code 414 when the CW signal 412 from the mobile device 402 is available.

[0053] Typically, positioning involves two states: ambient channel state information (CSI) sensing and backscatter CSI sensing. During ambient CSI sensing, Figure 4 The mobile device 402 receives and records CSI information as a reference through different communication modules on different frequency bands. Figure 4 In the example, different communication modules include, but are not limited to, Global System for Mobile Communications (GSM) module 404 (also known as 5G signal module), WiFi module 406, and Bluetooth (BT) module 408.

[0054] Mobile device 402 sends a CW signal 412 to initiate a response from one or more RFID tags 106. In one embodiment, mobile device 402 is used to record response codes, such as code 414, sent from different RFID tags 106. Typically, the RFID tags 106 are self-organizing and are used to respond one after another with their identification codes.

[0055] In one embodiment, using a backscattering circuit 108, RFID tags 106 are used to scatter ambient RF signals while responding to a mobile device 402 with their identification codes. The mobile device 402 is used to identify one or more identification codes and scattering patterns, as well as CSI information with and without scattering. By comparing the differences in CSI information, the distance to a particular RFID tag 106 can be estimated.

[0056] Figure 6 An example of distance estimation in conjunction with aspects of the disclosed embodiments is shown. In this example, mobile device 602 is used to detect environmental CSI signals s(t) from communication module 604, which may include one or more of a WiFi module, Bluetooth module, or 5G site. In this example, the environmental CSI signals s(t) are not controlled by mobile device 602.

[0057] In one embodiment, the RFID tag 106 and the backscattering module 108 are included. Figure 1 RFID module or device 150 is used with attenuation code And the delayed τ-reflected CSI signal s(t). Attenuation code For mobile device 602, this is known. The scattering path can be enabled and disabled by turning the CW signal on and off. This makes the delay τ the only unknown that needs to be estimated. The delay τ can be estimated independently for each RFID tag 150 and each frequency band. Average delay estimation can improve the accuracy of distance estimation.

[0058] Typically, transceiver hardware for mobile devices is manufactured in a Time Division Duplex (TDD) manner. This means that each frequency band can be configured to transmit or receive mode relative to a specific time slot. However, for typical mobile devices, it is usually not possible to transmit and receive in different frequency bands. The multi-band scattering method of the disclosed embodiments enables CW transmission in one frequency band and simultaneous reception in multiple frequency bands.

[0059] Figure 7Interactive Synthetic Aperture Radar (SAR) operation combining aspects of the disclosed embodiments is illustrated. In this example, mobile device 702 moves along a known movement path 706. The distance to the target or tag module 150 (RFID tag 106 and backscatter module 108) is estimated along movement path 706. By weighting the combined distance estimates from different locations, the position of tag 150 can be located with enhanced accuracy. It should be noted that the positioning accuracy typically corresponds to the direction of movement path 706. For accurate three-dimensional positioning, mobile device 702 should move in three directions.

[0060] exist Figure 7 In this example, tag 150 is a passive tag. Therefore, tag 150 in this example is not used to generate sound, vibration, or light in a manner that could help a user locate the position of tag 150. In one embodiment, location or position information may be displayed or otherwise presented on the display or user interface of mobile device 702. In this way, a user can refer to the display of mobile device 702 to locate or otherwise identify the position of tag 150.

[0061] For example, in one embodiment, mobile device 702 can display a view in front of it using its camera. A hairpin indicator can be used, which can be minimized while improving positioning accuracy. In one embodiment, the graphical user interface (GUI) or display of mobile device 702 can be used to suggest certain movements to the user. The camera, camera inertial sensor, and / or time-of-flight (ToF) camera of mobile device 702 can be used together to monitor whether the user moves mobile device 702 as instructed and record the movement path 706 of mobile device 702 for SAR operations. Through this interactive movement, the accuracy of tag positioning can be improved in three dimensions until the user finds the tag.

[0062] Figure 8 An example of a method 800 incorporating aspects of the disclosed embodiments is shown. In one embodiment, a portion of an identification signal generated by an RFID tag is received 802 by a backscattering module. The backscattering module is used to generate 804 a voltage output related to the power level of a portion of the identification signal. The voltage output is used to control 806 the reflectivity of an antenna. In one embodiment, the antenna may be coupled to the backscattering module. The antenna is used to backscatter the signal 808 within a frequency band related to the voltage output for RFID tag location 810.

[0063] The disclosed embodiments extend multi-band operation for RFID positioning. This mitigates multipath effects common in single-band operation and enables better distance estimation via multi-band CSI. Mobile devices can be used to activate passive RFID tags, reducing the need for RFID reader sites and improving positioning accuracy due to better SNR. Existing features of mobile devices, such as, but not limited to, accelerometers, camera images, microphones, etc., are used to improve movement path estimation and positioning.

[0064] In one embodiment, camera information from a mobile device can be used to display location information in augmented reality (AR) and / or virtual reality (VR). In an alternative embodiment, the location information can be presented in any suitable format or manner.

[0065] Therefore, although the essential novel features of the invention applicable to exemplary embodiments thereof have been shown, described, and pointed out herein, it should be understood that those skilled in the art can make various omissions, substitutions, and changes to the form and details of the illustrated apparatus and methods, as well as the operational procedures, without departing from the spirit and scope of the invention. Furthermore, all combinations of elements that are explicitly intended to perform substantially the same function in substantially the same manner to achieve the same result are within the scope of the invention. Moreover, it should be recognized that structures and / or elements shown and / or described in connection with any form or embodiment of the disclosed invention can be incorporated as general design choices into any other form or embodiment disclosed, described, or suggested. Therefore, its intent is limited only as indicated by the scope of the appended claims.

Claims

1. An apparatus (150), characterized in that, Includes a passive RFID tag (106) and a backscattering module (108), wherein: A portion (114) of the identification signal (112) generated by the RFID tag (106) is received by the backscattering module (108), which is used to: Generate a voltage output (132) related to the power level of the portion (114) of the identification signal (112). The voltage output (132) is used to control the reflectivity of the antenna (138) and enable the antenna (138) to backscatter the signal in the frequency band associated with the voltage output (132) for the location of the RFID tag (106).

2. The apparatus (100) according to claim 1, characterized in that, The backscattering module (108) includes an envelope detector (130), a FET transistor (134), and a broadband antenna (138), wherein the portion (114) of the identification signal (112) is the input of the envelope detector (130), and the envelope detector (130) is used to generate a voltage output (132) related to the power level of the portion (114) of the identification signal (112), the voltage output (132) being used to switch the FET transistor (134) to an on state and an off state.

3. The apparatus (100) according to any one of claims 1 or 2, characterized in that, The RFID tag (106) is used to receive RF signals in a first frequency band and generate scattered signals in multiple frequency bands.

4. The apparatus (100) according to any one of the preceding claims, characterized in that, The RFID tag (106) is used to generate the identification signal in response to a received RF signal.

5. An RFID tag positioning system (400), characterized in that, include: The mobile communication device (402), the passive RFID tag (106), and the backscattering module (108) include: A portion (114) of the identification signal (112) generated by the RFID tag (106) in response to the RF signal (412) sent by the mobile communication device (402) is received by the backscattering module (108), and the backscattering module (108) is used to: Generate a voltage output (132) related to the power level of the portion (114) of the identification signal (112). The voltage output (132) is used to control the reflectivity of the antenna (138) coupled to the backscatter module (108) and enable the antenna (138) to backscatter the signal in the frequency band associated with the voltage output (132) for the location of the RFID tag (106).

6. The system (400) according to claim 5, characterized in that, The mobile communication device (402) is used for: Receive and record channel state information of environmental signals transmitted from wireless communication devices; Detect the scattered signal from the backscattering module (108) that corresponds to the environmental signal; The distance of the RFID tag (106) is estimated by comparing the difference between the channel state information corresponding to the scattered signal and the ambient signal.

7. The system (400) according to any one of claims 5 or 6, characterized in that, The mobile communication device (402) is used to control the reflectivity of the antenna (138) to enable and disable the transmission of the scattered signal.

8. The system (400) according to any one of claims 5 to 7, characterized in that, The mobile communication device (402) is used to transmit the RF signal on a first frequency band and receive scattered signals from one or more RFID tags (106) on multiple frequency bands.

9. The system (400) according to any one of claims 5 to 8, characterized in that, The mobile communication device (402) is also used for: Identify the movement path (706) of the mobile communication device (402); The distance from the RFID tag (106) to the mobile communication device (402) is calculated at different locations along the movement path (706); The RFID tag (106) is located based on the distance calculated at different locations along the movement path.

10. A method (800), characterized in that, include: The part that receives (802) the identification signal generated by the RFID tag; Generate (804) a voltage output related to the power level of said portion of the identification signal; The output voltage is used to control the reflectivity of the (806) antenna; The antenna (808) backscatters the signal in a frequency band related to the voltage output; The RFID tag is located (810) based on the backscattered signal.

11. The method (800) according to claim 10, characterized in that, Also includes: Channel state information of environmental signals sent from mobile communication devices is received and recorded using wireless communication protocols; Detect the scattered signal from the backscattering module corresponding to the environmental signal; The distance of the RFID tag is estimated by comparing the difference between the channel state information corresponding to the scattered signal and the ambient signal.

12. The method (800) according to claim 11, characterized in that, It also includes the mobile communication device transmitting the RF signal on a first frequency band and receiving scattered signals from one or more RFID tags on multiple frequency bands.

13. The method (800) according to any one of claims 10 to 12, characterized in that, Also includes: Identify the movement path of the mobile communication device; Calculate the distance from the RFID tag to the mobile communication device at different locations along the movement path; The RFID tag is located based on the distance calculated at different locations.

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