Mobile phone based RFID tag localization

Abstract

An apparatus includes a passive RFID tag and a backscatter module. A portion of an identification signal generated by the RFID tag responsive to an RF signal transmitted by an RFID reader is received by the backscatter module. The backscatter module is configured to generate a voltage output that correlates to a power level of the portion of the identification signal. The backscatter module uses the voltage output to control a reflectivity of an antenna and enables the antenna to backscatter signals within a frequency band relative to the voltage output for RFID tag localization.

Description

[0001] MOBILE PHONE BASED RFID TAG LOCALIZATION

[0002] FIELD

[0003] The aspects of the disclosed embodiments relate generally to Radio Frequency Identification (RFID) tag localization and more particularly to mobile phone based RFID tag localization.

[0004] BACKGROUND

[0005] RFID tag-based object localization is a popular and effective approach to precisely locate and track objects in various applications. By utilizing tags, which are typically small electronic devices equipped with wireless communication capabilities, objects can be accurately identified and their positions determined in real-time. This technology has found widespread use in asset tracking, supply chain management, indoor navigation, and many other fields where knowing the precise location of objects is crucial.

[0006] Tag-based object localization generally revolves around attaching or embedding tags onto objects of interest. These tags emit signals that can be detected and interpreted by receivers or readers strategically placed in the environment. By measuring the signal strength or utilizing other localization techniques, such as time-of-fhght or trilateration, the position of the tagged object can be determined with a high degree of accuracy.

[0007] While tag-based object localization offers numerous advantages, there are also drawbacks. The cost of implementing tags, particularly with multiple tags at large scales, can be significant. Depending on the tag type, batteries may need to be replaced periodically, incurring maintenance costs and requiring careful consideration of power management strategies.

[0008] Thus, there is a need for an improved apparatus and method for RFID tag localization. Accordingly, it would be desirable to provide an apparatus and method that addresses at least some of the problems described above.

[0009] SUMMARY

[0010] The aspects of the disclosed embodiments are directed to an apparatus and methods for RFID tag localization. In particular, the aspects of the disclosed embodiments are directed to the use of a mobile communication device to locate a passive RFID tag. According to a first aspect, the above and further implementations and advantages are obtained by an apparatus. In one embodiment, the apparatus includes a passive RFID tag and a backscatter module. A portion of an identification signal generated by the RFID tag is received by the backscatter module. The backscatter module is configured to generate a voltage output that correlates to a power level of the portion of the identification signal. The voltage output is used to control a reflectivity of an antenna. In one embodiment, the antenna can be coupled to the backscatter module. The antenna is configured to backscatter signals within a frequency band relative to the voltage output for localization of the RFID tag. The aspects of the disclosed embodiments enable accurate localization of a passive RFID tag.

[0011] In a possible implementation form the backscatter module includes an envelope detector, a switching device and a wideband antenna. In one embodiment, the switching device comprises a field effect transistor (FET) device. The portion of the identification signal is an input to the envelope detector and the envelope detector is configured to generate the voltage output that correlates to a power level of the portion of the identification signal. The voltage output is configured to switch the FET transistor between a conducting state and a non-conducting state. The voltage that is presented at the gate of the FET is configured to control the reflectivity of the antenna. The antenna is configured to backscatter signals within its frequency band based on the control voltage. The aspects of the disclosed embodiments enable accurate localization of a passive RFID tag.

[0012] In a possible implementation form, the RFID reader is, or is comprised in, a mobile communication device. Using a mobile communication device for tag localization reduces the need for RFID reader stations and improves localization accuracy since the signal-to-noise ratio (SNR) will increase as the mobile communication device moves closer to the target. Existing features of the mobile communication device can be used to improve moving path estimation and tag localization.

[0013] In a possible implementation form the mobile communication device is configured to receive and record channel state information (CSI) for an ambient signal sent using a wireless communication protocol; detect a scattered signal from the backscatter module corresponding to the ambient signal; and estimate a range of the RFID tag by comparing a difference between channel state information corresponding to the scattered signal and the ambient signal. The aspects of the disclosed embodiments enable transmitting the CW signal on one band and receiving the scattered signal(s) over multiple bands simultaneously, thus providing multiple band operation. Multipath interference in a single-frequency operation case is mitigated and there is better distance estimation with multiple band CSI.

[0014] In a possible implementation form the mobile communication device is configured to control the reflectivity of the antenna to enable and disable a transmission of the scattered signal(s). The a code is known to the mobile communication device, and by switching the CW signal on and off, the scattering path can be enabled and disabled. This leaves only the delay T as the unknown to be estimated. The delay can be estimated for each RFID tag and at each frequency band independently. Averaging the delay estimation can increase the accuracy of the range estimation.

[0015] In a possible implementation form the mobile communication device is configured to transmit an RF signal to one or more RFID tags over a first frequency band and receive scattered signals from one or more of the RFID tags over multiple frequency bands. The multiple band scattering approach of the disclosed embodiments enables transmitting CW at one band and receiving at multiple bands simultaneously.

[0016] In a possible implementation form, a movement path of the mobile communication device can be identified and a range of the RFID tag to the mobile device calculated at different locations along the movement path. The RFID tag can be localized based on the calculated range at different locations. By weighting combined range estimation at different locations, the position of the tag can be localized with enhanced accuracy.

[0017] According to a second aspect, the above and further implementations and advantages are obtained by an RFID tag localization system. In one embodiment, the system includes an RFID reader, a passive RFID tag and a backscatter module. A portion of an identification signal generated by the RFID tag responsive to an RF signal transmitted by the RFID reader is received by the backscatter module. The backscatter module is configured to generate a voltage output that correlates to a power level of the portion of the identification signal. The voltage output is used to control a reflectivity of an antenna coupled to the backscatter module. The antenna is configured to backscatter signals within a frequency band relative to the voltage output for localization of the RFID tag. The aspects of the disclosed embodiments enable accurate localization of a passive RFID tag.

[0018] In a possible implementation form, the mobile communication device is configured to receive and record channel state information for an ambient signal sent from the mobile communication device using a wireless communication protocol; detect a scattered signal from the backscatter module corresponding to the ambient signal; and estimate a range of the RFID tag by comparing a difference between channel state information corresponding to the scattered signal and the ambient signal. The aspects of the disclosed embodiments enable accurate localization of a passive RFID tag.

[0019] In a possible implementation form the mobile communication device is configured to control the reflectivity of the antenna to enable and disable a transmission of the scattered signal. The aspects of the disclosed embodiments enable accurate localization of a passive RFID tag.

[0020] In a possible implementation form the mobile communication device is configured to transmit the RF signal over a first frequency band and receive scattered signals from one or more RFID tags over multiple frequency bands. Multipath interference in a single-frequency operation case is mitigated and there is better distance estimation with multiple band CSI.

[0021] In a possible implementation form the mobile communication device is further configured to identify a movement path of the mobile communication device; calculate a range of the RFID tag to the mobile communication device at different locations along the movement path; and localize the RFID tag based on the calculated range at different locations. The aspects of the disclosed embodiments can enhance tag localization accuracy.

[0022] According to a third aspect, the above and further implementations and advantages are obtained by a method. In one embodiment, the method includes receiving a portion of an identification signal generated by an RFID tag; generating a voltage output that correlates to a power level of the portion of the identification signal; controlling a reflectivity of an antenna with the output voltage; enabling the antenna to backscatter signals within a frequency band relative to the voltage output; and localizing the RFID tag based on the backscattered signals. The aspects of the disclosed embodiments enable accurate localization of a passive RFID tag. In a possible implementation form, the method further includes receiving and recording channel state information for an ambient signal sent from a mobile communication device using a wireless communication protocol; detecting a scattered signal from a backscatter module corresponding to the ambient signal; and estimating a range of the RFID tag by comparing a difference between channel state information corresponding to the scattered signal and the ambient signal. The aspects of the disclosed embodiments provide better distance estimation with multiple band CSI.

[0023] In a possible implementation form, the method further includes the mobile communication device transmitting the RF signal over a first frequency band and receiving scattered signals from one or more RFID tags over multiple frequency bands. The aspects of the disclosed embodiments enable transmitting the CW signal on one band and receiving the scattered signal(s) over multiple bands simultaneously, thus providing multiple band operation. Multipath interference in a single-frequency operation case is mitigated and there is better distance estimation with multiple band CSI.

[0024] In a possible implementation form, the method further includes identifying a movement path of the mobile communication device; calculating a range of the RFID tag to the mobile communication device at different locations along the movement path; and localizing the RFID tag based on the calculated range at different locations. The aspects of the disclosed embodiments enable using existing features of the mobile device to improve moving path estimation and localization.

[0025] These and other aspects, implementation forms, and advantages of the exemplary embodiments will become apparent from the embodiments described herein considered in conjunction with the accompanying drawings. It is to be understood, however, that the description and drawings are designed solely for purposes of illustration and not as a definition of the limits of the disclosed invention, for which reference should be made to the appended claims. Additional aspects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the aspects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the following detailed portion of the present disclosure, the aspects of the disclosed embodiments will be explained in more detail with reference to the example embodiments shown in the drawings, in which like references indicate like elements and:

[0027] Figure 1 illustrates a block diagram of an exemplary system incorporating aspects of the disclosed embodiments.

[0028] Figure 2 illustrates a block diagram of an exemplary system incorporating aspects of the disclosed embodiments.

[0029] Figure 3 illustrates a schematic circuit diagram of an exemplary backscatter module incorporating aspects of the disclosed embodiments.

[0030] Figure 4 illustrates a block diagram of an exemplary system incorporating aspects of the disclosed embodiments.

[0031] Figure 5 illustrates a timing diagram for wideband localization in accordance with aspects of the disclosed embodiments.

[0032] Figure 6 illustrates range estimation in accordance with the aspects of the disclosed embodiments.

[0033] Figure 7 illustrates range estimation with a moving mobile device in accordance with the aspect of the disclosed embodiments.

[0034] Figure 8 is a flow chart illustrating a process flow in accordance with the aspects of the disclosed embodiments.

[0035] DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

[0036] Figure 1 illustrates a block diagram of an exemplary system 100 configured for mobile phone based RFID tag localization. The aspects of the disclosed embodiments are directed to accurately locating a battery less passive RFID tag. When the RFID tag is a passive tag, the tag does not make sound or vibrate as would an active tag. This can require higher localization accuracy and user interaction to help the user find the tag.

[0037] As shown in the example of Figure 1, a RFID reader 102 is configured to transmit a continuous wave (CW) signal 110. The apparatus 150, which in one embodiment includes an RFID tag or chipset 106, is configured to receive the signal 110 and generate an identification signal 112. In one embodiment, a portion 114 of an identification signal 112 generated by the RFID tag 106 is received by the backscatter module 108. Referring also to Figure 2, in one embodiment, the backscatter module 108 is configured to generate a voltage output 132 that correlates to a power level of the portion 114 of the identification signal 112. The voltage output 132 is used to control a reflectivity of an antenna 138 coupled to the backscatter module 108 and enable the antenna 138 to backscatter signals within a frequency band relative to the voltage output 132 for localization of the RFID tag 106.

[0038] At low frequency, the coverage and energy transferring efficiency is high, but server multiple path can limit the accuracy of the localization. The aspects of the disclosed embodiments are directed to a multiple frequency operated tag, which can mitigate the problems associated with single-frequency designs.

[0039] As illustrated in Figure 2, in one embodiment, the RFID chipset 106 in this example includes an antenna 104, a matching network or circuit 120, an RF energy harvesting module or device 122, a micro-controller unit (MCU) or device 124 and a modulator block or device 128. In alternate embodiments, the RFID chipset 106 can include any suitable components for a passive and battery less RFID tag.

[0040] In operation, the RFID reader 102 is configured to send or transmit the continuous wave (CW) signal 110. In one embodiment, the continuous wave signal 110 can comprise an approximately 918 Megahertz (MHz) signal. In alternate embodiments, the CW signal 110 sent by the RFID reader 102 comprises any suitable signal, other than including a 918 MHz signal.

[0041] The signal 110 is received by the antenna 104. The matching network 120 is configured to pass the signal 110 to the energy harvesting block 122. The energy harvesting block 122 is configured to store energy from the signal 110 and power the micro-controller unit 124.

[0042] The micro-controller unit 124 is configured to transmit an RFID identification code 126. In one embodiment, the RFID identification code 126 is a binary code. In alternate embodiments, the RFID code 126 is any suitable code. The micro-controller unit 124 can be configured to repeatedly transmit the RFID identification code 126.

[0043] In one embodiment, the RFID identification code 126 is up-converted by the modulator 128 to 918 MHz and transmitted by the matching network 120 and antenna 104 as signal 112. Signal 112 can comprise an On-Off Keying (OOK) signal or an Amplitude Shift Keying (ASK) signal, as shown in Figure 4, for example. Generally, the transmission of the signal 112 is in the same band as the transmission of signal 110 from the RFID reader 102.

[0044] The backscatter circuit or module 108 is generally configured to extend the transmission of the identification code 126 to a wideband. As shown in the example of Figure 2, in one embodiment, the backscatter circuit 108 comprises an envelope detector 130, a voltage gain circuit 134 and a wideband antenna 138. In one embodiment, the voltage gain circuit 134 comprises a field effect transistor (FET) device. In alternate embodiments, the voltage gain circuit 134 can comprise any suitable voltage gain device, other than including a field effect transistor device.

[0045] The envelope detector 130 is generally configured to couple the part 114 of signal 112 from the RFID chipset 106 and generate a voltage output 132 that correlates to the power level of the signal 112. The voltage output or signal 132 generally comprises the RFID code 126 transmitted from the MCU 124.

[0046] In one embodiment, the voltage generated from the envelope detector 130 is used for switching the voltage gain circuit or FET 134. Generally, the FET 134 is conducting with a high voltage input that connects the antenna 138 to ground, where the signal will be absorbed. When the input to the FET 134 is a low voltage input, the FET 134 is not conducting, or is shut down, also referred to as an open state. In this case, the signal from the antenna 138 will be totally reflected. The voltage that is presented at the gate of the FET 134 controls the reflectivity of the antenna 138. The antenna 138 will backscatter signals within its frequency band in respect to the control voltage, which can be used for localization of the RFID tag 106.

[0047] Figures 3 illustrates a schematic diagram of an exemplary backscatter circuit 300. In this example, the input 302 couples the part 114 of the output 112 from the RFID chipset 106 of Figure 2. The input 302 passes a coupling capacitor Cl to a diode DI. Transmission line TL is a quarter wavelength for the 918 MHz signal 110 of Figures 1 and 2. Resistor R1 and capacitor C2 act a low pass filter. The combination of the diode DI, resistor Rl, capacitor C2 and transmission line TL together act as the envelope detector 130 of Figure 2 that will convert the ASK or OOK signal into the voltage output. QI in this example is an FET transistor which is configured to conduct with a positive gate voltage and disconnect with a negative gate voltage. When FET transistor QI is conducting, the patch antenna 304 is configured to receive a signal in the 2-6 Gigahertz range. The received signal is absorbed by conducting to ground through the FET QI. When FET QI is in a disconnected or open state, the patch antenna 304 will be fully reflective.

[0048] Figure 4 illustrates an exemplary schematic block diagram of a system 400 incorporating aspects of the disclosed embodiments. In this example, the system 400 employs the use of a mobile communication device or mobile phone 402 for RFID tag localization. The use of a mobile communication device 402 reduces the need for RFID reader stations and improves localization accuracy since the signal -to-noise ratio will increase as the mobile device 402 moves closer to the target RFID tag 106.

[0049] In one embodiment, the mobile communication device 402 can comprise a mobile phone. Although a mobile communication device or phone is generally referred to herein, the aspects of the disclosed embodiments are not so limited. In alternate embodiments, mobile communication device 402 can include any suitable portable device with wireless connectivity, including for example, virtual reality (VR) goggles and smart wearable devices.

[0050] In this example, the RFID chipset 106 is enabled by receiving the continuous wave (CW) signal 412 from the mobile device 402. The CW signal 412 transfers energy to all RFID tags 106 within a predetermined area. Although the 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 so limited. In alternate embodiments, the aspects of the disclosed embodiments can be implemented with any suitable number of RFID tags.

[0051] The energized RFID tag(s) 106 will respond with an Identification Code 414. Generally, the identification code 414 is transmitted back to the mobile device 402 as a repeated ASK or OOK transmission.

[0052] During this process, the mobile device 402 is configured to identify the number of RFID tags 106 that are nearby, or within the predetermined area, together with their corresponding Identification Code. Figure 5 illustrates an exemplary timing diagram 500 for the wideband localization protocol in accordance with the aspects of the disclosed embodiments. Referring to Figures 4 and 5, in one embodiment, an RFID tag 106 is controlled by the mobile device 402 sending the CW signal 412. The RFID tag(s) 106 is configured to scatter and / or transmit the identification code 414 when the CW signal 412 from the mobile device 402 is available.

[0053] Generally, there are two states of localization, ambient channel state information (CSI) sensing and backscattering CSI sensing. During ambient CSI sensing, the mobile device 402 of Figure 4 receives and records CSI information by the different communication modules of the mobile device 402 at different bands as reference. In the example of Figure 4, the different communication modules include, but are not limited to a Global System for Mobile Communication module 404, also referred to as a 5G signal module, a WiFi module 406 and a Bluetooth (BT) module 408.

[0054] The mobile device 402 sends the CW signal 412 to initiate a response from one or more RFID tags 106. In one embodiment, the mobile device 402 is configured to record a responsive code, such as code 414, transmitted from different RFID tags 106. Generally, the RFID tags 106 are self-organized and configured to respond with their identification code, one after each other.

[0055] In one embodiment, using the backscatter circuit 108, the RFID tags 106 are configured to scatter an ambient RF signal environment while they respond to the mobile device 402 with their identification code. The mobile device 402 is configured to recognize the identification code(s) and the scattering pattern, as well as CSI information with and without scattering. By comparing CSI information differences, the range of a particular RFID tag 106 can be estimated.

[0056] Figure 6 illustrates one example of range estimation incorporating aspects of the disclosed embodiments. In this example, the mobile device 602 is configured to detect an ambient CSI signal s(t) from the communication module 604, which can include one or more of a WiFi module, Bluetooth module or a 5G station. In this example, the ambient CSI signal s(t) is not controlled by the mobile device 602.

[0057] In one embodiment, the RFID module or apparatus 150 of Figure 1, which includes the RFID tag 106 and backscatter module 108, is configured to reflect the CSI signal s(t) with attenuation code acodeand delay T. The attenuation code acodeis known to the mobile device 602. By switching the CW signal on and off, the scattering path can be enabled and disabled. This leaves the delay T as the only unknown to be estimated. The delay T can be estimated for each RFID tag 150 and at each frequency band independently. Averaging delay estimation can increase the accuracy of the range estimation.

[0058] Generally, transceiver hardware for mobile devices are made in a Time Division Duplex (TDD) manner. This means that each band can be set in either transmitting or receiving mode with respect to a certain time slot. However, transmitting and receiving in different bands is generally not possible with the typical mobile device. The multiple band scattering approach of the disclosed embodiments enables transmitting CW in one band and receiving in multiple bands simultaneously.

[0059] Figure 7 illustrates interactive Synthetic Aperture Radar (SAR) operation incorporating aspects of the disclosed embodiments. In this example, the mobile device 702 is moving along a known movement path 706. The range to the target or tag module 150 (RFID tag 106 and backscatter module 108) is estimated along the movement path 706. By weighting the combined range estimation at different locations, the position of the tag 150 can be localized with enhanced accuracy. It should be noted that the localization accuracy generally corresponds to the direction of the movement path 706. To have accurate three-dimensional localization, the mobile device 702 should be moved in three directions.

[0060] In the example of Figure 7, the tag 150 is a passive tag. Thus, the tag 150 in this example is not configured to produce sound, vibration or light in a manner that can be used to assist the user in locating the position of the tag 150. In one embodiment, position or location information can be displayed or otherwise presented on or via the display or user interface of the mobile device 702. In this manner, the user can refer to the display of the mobile device 702 to locate or otherwise identify a position of the tag 150.

[0061] For example, in one embodiment, the mobile device 702 can use the camera of the mobile device 702 to display a view in front of the mobile device 702. A hairpin indicator can be used that could be minimized while localization accuracy is enhanced. In one embodiment, the graphical user interface (GUI) or display of the mobile device 702 can be configured to suggest certain movement to the user. The camera, camera-inertia sensor and / or Time of Flight (ToF) camera of the mobile device 702 can be jointly used to monitor if the user is moving the mobile device 702 as indicated and record the movement path 706 of the mobile device 702 for SAR operation. With this interactive movement, the tag localization accuracy can improve in three dimensions, until the user locates the tag.

[0062] Figure 8 illustrates one example of a method 800 incorporating aspects of the disclosed embodiments. In one embodiment, a portion of an identification signal generated by an RFID tag is received 802 by a backscatter module. The backscatter module is configured to generate 804 a voltage output that correlates to a power level of the portion of the identification signal. The voltage output is used to control 806 a reflectivity of an antenna. In one embodiment, the antenna can be coupled to the backscatter module. The antenna is configured to backscatter 808 signals within a frequency band relative to the voltage output for localization 810 of the RFID tag.

[0063] The aspects of the disclosed embodiments extend multiple band operation for RFID localization. This mitigates multipath in single-frequency operation cases and provides better distance estimation with multiple band CSI. A mobile device can be used to activate a passive RFID tag, which reduces the need for RFID reader stations and can improve localization accuracy due to a better SNR. Existing features of the mobile device, such as for example, but not limited to acceleration meter, camera image, microphone are used to improve movement path estimation and improve localization.

[0064] In one embodiment, the camera information of the mobile device can be used to display localization information in augmented reality (AR) and / or virtual reality (VR). In alternate embodiments, the localization information can be presented in any suitable format or manner.

[0065] Thus, while there have been shown, described, and pointed out, fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omissions, substitutions and changes in the form and details of apparatuses and methods illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the presently disclosed invention. Further, it is expressly intended that all combinations of those elements, which perform substantially the same function in substantially the same way to achieve the same results, are within the scope of the invention. Moreover, it should be recognized that structures and / or elements shown and / or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

CLAIMSWhat is claimed is:

1. An apparatus (150) comprising a passive RFID tag (106) and a backscatter module (108), wherein: a portion (114) of an identification signal (112) generated by the RFID tag (106) is received by the backscatter module (108), and the backscatter module (108) is configured to: generate a voltage output (132) that correlates to a power level of the portion (114) of the identification signal (112); and use the voltage output (132) to control a reflectivity of an antenna (138) and enable the antenna (138) to backscatter signals within a frequency band relative to the voltage output (132) for localization of the RFID tag (106).

2. The apparatus (100) according to claim 1, wherein the backscatter module (108) comprises an envelope detector (130), an FET transistor (134) and a wideband antenna (138), wherein the portion (114) of the identification signal (112) is an input to the envelope detector (130) and the envelope detector (130) is configured to generate the voltage output (132) that correlates to a power level of the portion (114) of the identification signal (112), and the voltage output (132) is configured to switch the FET transistor (134) between a conducting and a nonconducting state.

3. The apparatus (100) according to any one of claims 1 or 2, wherein the RFID tag (106) is configured to receive an RF signal on a first frequency band and generate scattered signals over multiple frequency bands.

4. The apparatus (100) according to any one of the preceding claims, wherein the RFID tag (106) is configured to generate the identification signal responsive to a received RF signal.

5. An RFID tag localization system (400) comprising: a mobile communication device (402), a passive RFID tag (106) and a backscatter module (108), wherein: a portion (114) of an identification signal (112) generated by the RFID tag (106) responsive to an RF signal (412) transmitted by the mobile communication device (402) is received by the backscatter module (108), and the backscatter module (108) is configured to:generate a voltage output (132) that correlates to a power level of the portion (114) of the identification signal (112); and use the voltage output (132) to control a reflectivity of an antenna (138) coupled to the backscatter module (108) and enable the antenna (138) to backscatter signals within a frequency band relative to the voltage output (132) for localization of the RFID tag (106).

6. The system (400) according to claim 5, wherein the mobile communication device (402) is configured to: receive and record channel state information for an ambient signal sent from a wirelsss communication device; detect a scattered signal from the backscatter module (108) corresponding to the ambient signal; and estimate a range of the RFID tag (106) by comparing a difference between 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, wherein the mobile communication device (402) is configured to control the reflectivity of the antenna (138) to enable and disable a transmission of the scattered signal.

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

9. The system (400) according to any one of claims 5 to 8, wherein the mobile communication device (402) is further configured to: identify a movement path (706) of the mobile communication device (402); calculate a range of the RFID tag (106) to the mobile communication device (402) at different locations along the movement path (706); and localize the RFID tag (106) based on the calculated range at different locations along the movement path.

10. A method (800) comprising: receiving (802) a portion of an identification signal generated by an RFID tag;generating (804) a voltage output that correlates to a power level of the portion of the identification signal; controlling (806) a reflectivity of an antenna with the output voltage; enabling (808) the antenna to backscatter signals within a frequency band relative to the voltage output; and localizing (810) the RFID tag based on the backscattered signals.

11. The method (800) according to claim 10, further comprising: receiving and recording channel state information for an ambient signal sent from a mobile communication device using a wireless communication protocol; detecting a scattered signal from a backscatter module corresponding to the ambient signal; and estimating a range of the RFID tag by comparing a difference between channel state information corresponding to the scattered signal and the ambient signal.

12. The method (800) according to claim 11, further comprising the mobile communication device transmitting the RF signal over a first frequency band and receiving scattered signals from one or more RFID tags over multiple frequency bands.

13. The method (800) according to any one of claims 10 to 12, further comprising: identifying a movement path of the mobile communication device; calculating a range of the RFID tag to the mobile communication device at different locations along the movement path; and localizing the RFID tag based on the calculated range at different locations.

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