Detuning detection and compensation for inductive coupling systems

Abstract

To provide suitable techniques for operating an inductive coupling reader.SOLUTION: This disclosure describes techniques for operating an inductive coupling reader. The techniques include operations comprising: detecting a change in a resonance frequency of the inductive coupling reader; comparing the change in the resonance frequency to a threshold; determining that the change in the resonance frequency falls outside the threshold; and activating a compensation circuit to offset the change in the resonance frequency of the inductive coupling reader in response to determining that the change in the resonance frequency falls outside the threshold.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This specification generally relates to radio frequency identification (RFID) systems, and more particularly, to techniques for reducing harmful interference effects in RFID systems, but is not limited thereto.

Background Art

[0002] An RFID system is a system that uses radio frequency transponders (e.g., tags) to identify articles of interest. Each radio frequency transponder is attached to a corresponding article or in its vicinity and contains information for identifying the article. When identification is required, a radio frequency reader unit (e.g., an interrogator) is used to excite (e.g., interrogate) the transponder on the article, and the transponder sends back an identification signal (including the identification information of the article) to the reader unit. Thereafter, the reader unit uses the identification information received from the transponder to execute any of a number of different RFID applications. For example, functions such as asset management, inventory tracking, access control, etc. can be executed using the identification information.

Summary of the Invention

[0003] In some specific embodiments, a system and method for operating an inductive coupling reader are provided. The disclosed system and method include detecting a change in the resonant frequency of the inductive coupling reader, comparing the change in the resonant frequency with a threshold, determining that the change in the resonant frequency exceeds the threshold, and in response to determining that the change in the resonant frequency exceeds the threshold, activating a compensation circuit to offset the change in the resonant frequency of the inductive coupling reader.

[0004] In some embodiments, the change in resonance frequency is caused by an external metal material in proximity to the inductive coupling reader, and the range of the inductive coupling reader is reduced as a result of the change in resonance frequency.

[0005] In some embodiments, detecting a change in resonance frequency includes measuring the amount of current flowing through the inductive coupling reader using a current sensor. In some embodiments, the amount of current flowing through the inductive coupling reader is compared to a predicted amount of current. In such cases, when the amount of current is less than the predicted amount of current by a given amount, it is determined that the change in resonance frequency exceeds a threshold.

[0006] In some embodiments, the amount of current flowing through the inductive coupling reader includes the current flowing through the antenna of the inductive coupling reader, and the given amount includes 10 percent of the predicted amount of current.

[0007] In some embodiments, the predicted amount of current is read from a look-up table. In some embodiments, the compensation circuit comprises one or more capacitors coupled in parallel to the resonant circuit of the inductive coupling reader.

[0008] In some embodiments, by comparing the current amount of current flowing through the inductive coupling reader to the predicted amount of current, proper operation of the inductive coupling reader is confirmed after activation of the compensation circuit.

[0009] In some embodiments, the threshold includes a first threshold, and the compensation circuit includes a first compensation circuit. In such a case, the plurality of operations include determining that a change in the resonance frequency exceeds the first threshold and is less than a second threshold, activating the first compensation circuit in response to determining that the change in the resonance frequency exceeds the first threshold and is less than the second threshold, determining that the change in the resonance frequency exceeds the first threshold and the second threshold, and activating a second compensation circuit in response to determining that the change in the resonance frequency exceeds the first threshold and the second threshold, wherein activating the second compensation circuit causes the resonance frequency to be offset by more than the first compensation circuit.

[0010] In some embodiments, activation of the first compensation circuit couples a first capacitor in parallel with the resonance circuit of the inductive coupling reader, and activation of the second compensation circuit couples a second capacitor larger than the first capacitor in parallel with the resonance circuit of the inductive coupling reader.

[0011] In some embodiments, the second capacitor includes the first capacitor and at least one other capacitor. In some embodiments, the operations further include placing the inductive coupling reader on a metal surface, measuring a detuning effect of the metal surface on the inductive coupling reader, and calculating an offset to compensate for the measured detuning effect, and calculating an offset provided by the compensation circuit.

[0012] In some embodiments, the compensation circuit includes a switch and one or more capacitors having a first terminal coupled to a first terminal of a capacitor of the resonance circuit of the inductive coupling reader and a second terminal coupled to the switch.

[0013] In some embodiments, the one or more capacitors are coupled to the switch via a diode. In some embodiments, the compensation circuit is activated by closing the switch to ground the second terminal of the one or more capacitors.

[0014] In some embodiments, the switch comprises a transistor. In some embodiments, the inductive coupling reader includes an RFID reader. A metal material in proximity to a conventional RFID reader typically reduces the range of the RFID reader because it changes the resonant frequency of the resonant circuit of this conventional RFID reader. In the disclosed embodiments, interference and detuning of the resonant circuit of the inductive coupling reader are detected, and in response, a switch to an additional parallel capacitance compensates for such detuning. In this way, the overall power efficiency and range of an inductive coupling reader such as an RFID reader are improved, which improves the overall efficiency and functionality of the computer.

[0015] The above summary is intended to provide an overview of the subject matter of this patent application and is not intended to provide an exclusive or exhaustive description of the subject matter of the invention. The following detailed description is for the purpose of providing further information regarding this patent application.

[0016] In the drawings, which are not necessarily drawn to scale, the same numbers in different figures may represent similar components. If the same number has different suffixes, it may represent different examples of similar components. The drawings generally illustrate, by way of example, the various embodiments discussed in this specification, but are not in any way limiting.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0018] The present disclosure particularly describes techniques for operating an inductive coupling reader. Specifically, in the disclosed techniques, interference and detuning of the resonant circuit of the inductive coupling reader are detected, and in response thereto, a switch is made to an additional parallel capacitance to compensate for such detuning. In this way, the overall power efficiency and range of an inductive coupling reader such as an RFID reader are improved, which improves the overall efficiency and functionality of the computer.

[0019] In an RFID system, problems occur when one or more external interference signals are present within the system's frequency band during a call operation. Such interference often causes misidentification of items-of-interest and malfunction reports in the RFID system. Such interference is often caused by metallic materials placed near the target system. Such metallic materials significantly reduce the range of the RFID caller, especially for changing the resonant frequency of the resonant circuit of the RFID caller. For example, when an inductive coupling reader (e.g., a 13.56 MHz RFID reader) is placed on a metallic surface, the apparent inductance of its antenna will change. Since the antenna is part of a parallel resonant circuit used for communication with an RFID transponder (e.g., a credential such as an RFID tag), the detuning of this circuit will reduce the actual performance (e.g., read range). Also, thereby, the RFID reader consumes more power to read a given RFID tag, wasting system resources.

[0020] To address the drawbacks of such typical scenarios, in the disclosed technology, the resonant circuit of the inductive coupling reader is detuned, and a situation where compensation is made for such detuning is detected. In particular, in the disclosed technology, a current sensor is used to measure the actual power consumption of the inductive coupling reader. If the power consumption does not meet a certain predetermined threshold (for example, when exceeding the threshold, falling below the threshold, or being outside the range of the threshold), the system determines that the resonant circuit is detuned (for example, due to the presence of a metallic material in proximity to the inductive coupling reader). In such a case, the inductive coupling reader employs a switchable tuning capacitor that allows the inductive coupling reader to add an additional parallel capacitance to mitigate and compensate for the detuning. Thereby, the performance of the inductive coupling reader can be restored and improved, which improves the power efficiency and range of the inductive coupling reader. For this reason, the overall efficiency and functionality of the computer are improved.

[0021] FIG. 1 is a block diagram showing an RFID system according to some embodiments. As shown, the RFID system 8 includes an RF reader unit 12 (inductive coupling reader) and a first plurality of RF identification tags 16, 18, 20, 22, 24, 26 respectively attached to corresponding articles of interest 34, 36, 38, 40, 42, and 44 and used for identifying the articles of interest. Examples of the articles of interest 34, 36, 38, 40, 42, and 44 include inventory, personnel, capital assets, or any other object for which it is desirable to track or monitor within a specific area. The number of articles that can be tracked by a specific reader is generally a matter of design choice.

[0022] The RF reader unit 12 can be a stationary unit (such as a wall-mounted proximity reader, etc.) or a portable unit that can be easily relocated. Usually, the coverage area provided by the RF reader unit is a function of the transmission power level of the reader, the antenna pattern of the reader transmission antenna, and the position and orientation of the reader at any given point in time.

[0023] In the normal operation of the exemplary system of FIG. 1, the RF reader unit 12 periodically calls its coverage area 52 to identify the item of interest currently located. That is, the reader unit 12 periodically transmits an RF call signal that serves as a "request" to transmit an identification signal for identifying the item of interest associated with each of the RF tags 16-26 in the area 52 within the coverage area 52. Each of the plurality of RF tags within the coverage area 52 receives the call signal and responds by sending its identification signal back to the calling reader. To prevent signal collisions in the channel between the RF tags and the reader within a particular coverage area, each of the plurality of RF tags can transmit its identification signal after a different pseudo-random delay time. When the RF reader receives an identification signal from one of the plurality of RF tags, it transmits a confirmation signal to that RF tag notifying that the identification information has been recorded. After receiving the confirmation signal, the identified RF tag does not retransmit its identification signal. If an RF tag does not receive a confirmation signal after waiting for a predetermined period after transmitting its identification signal, it is assumed that a collision has occurred in the channel, and the RF tag can retransmit its identification signal after another pseudo-random delay time. This can continue until each of the plurality of RF tags in the coverage area receives a confirmation signal from the reader. After receiving identification information from all the RF tags within its coverage area 52, the RF reader unit reports the gathered information to an appropriate entity.

[0024] Referring to FIG. 1, it is natural that there may be some interference between the RF reader unit 12 and the metal material. For example, the RF reader unit 12 may be mounted on a wall containing metal material. Such a metal material can affect the resonant circuit of the RF reader unit 12 and change the resonant frequency of the resonant circuit. As a result, the range of the RF reader unit 12 is reduced, and the RF reader unit 12 may misidentify or fail to identify an article far from the RF reader unit 12 within the area 52. That is, when a metal material exists in the vicinity of the RF reader unit 12, the size of the area 52 can be reduced. Also, since the resonant frequency of the RF reader unit 12 changes, the amount of power required for the proper operation of the RF reader unit 12 may increase.

[0025] According to the present disclosure, there are provided a method and an apparatus for suppressing the adverse effects of interference in an RFID system by compensating for a metal material determined to be the cause of a change in the resonant frequency of the RF reader unit 12.

[0026] FIG. 2 is a block diagram showing the RF reader unit 12 according to an embodiment of the present disclosure. As shown in the figure, the reader unit 12 includes a resonant circuit 210 including an antenna 60, a matching and tuning circuit 62, a transmitter 64, and a receiver 66, a controller 68, a current sensor 70, a comparator 72, a compensation circuit 220, and a user interface 74. In FIG. 2, the comparator 72 is depicted as a separate physical component, but it is also possible to implement part or all of the functions of the comparator 72 by the controller 68. That is, the functions of the comparator 72 can be realized not by hardware elements but by software by the controller 68. In such a case, the output of the current sensor 70 is directly supplied to the controller 68.

[0027] Controller 68 operates to control the operation of the reader unit 12 for the calling, tracking, and reporting of items of interest within the cover area 52 of the reader unit 12. Controller 68 is implemented using a digital processing device such as a general-purpose microprocessor, digital signal processor, reduced instruction set computer, multiple instruction set computer, or field programmable gate array. Also, one or more of the other functional blocks shown in FIG. 2 can also be digitally implemented in the same (or different) digital processor as Controller 68.

[0028] Transmitter 64 is used to generate a call signal that is sent to the cover area 52 via the antenna 60 during the calling operation (under the control of Controller 68). Also, as described above, Transmitter 64 can also be used to generate an acknowledgement signal that is sent to the tag after the identification information has been received from a specific RF tag. Receiver 66 operates to receive, demodulate, and decode the identification signal received from the RF tag disposed within the cover area 52, and deliver the resulting identification information to Controller 68.

[0029] The matching / tuning circuit 62 is a device that improves the efficiency with which the power available from the driver is delivered to the antenna 60. The impedance of the antenna 60 may be too high for a low-voltage driver to directly output sufficient power, and in such a case, the use of a matching network compensates for and matches the impedance of the antenna 60. In addition to impedance matching in the case of an inductive coupling RFID system, the matching / tuning circuit 62 can also be used to correctly set the resonant frequency of the antenna 60.

[0030] When the controller 68 collects tag identification information from the corresponding cover area 52, it reports the data to the appropriate entity via the user interface 74. Alternatively, the controller 68 can wait until all tag information about the cover area 52 has been collected before reporting the data. The user interface 74 can take many different forms depending on the type of reporting done within the system. For example, the interface 74 can be coupled to a video display for presenting the identification data to an operator. Alternatively, the interface 74 can include a modem for transferring and storing the data on a remote computer. In some embodiments, the reader unit of the large RFID system communicates via the interface 74 with a central control processor that generates system-wide reports by collecting (assembling), managing, and analyzing the identification information. The central control processor can also use this information to perform other system functions such as activating an electric door lock, sending a message to a user display (including the display of the reader itself), sounding an alarm, activating a recording device (e.g., a video camera), etc. Also, other forms of the user interface 74 can be used.

[0031] In some embodiments, the controller 68 detects a change in the resonant frequency of the reader 12. Specifically, the controller 68 detects a change in the resonant frequency of the resonant circuit 210. In some embodiments, the controller 68 detects a change in the resonant frequency of the reader 12, specifically based on the amount of current flowing through the resonant circuit 210. In particular, a current sensor 70 is coupled to the resonant circuit 210 to measure the amount of current flowing through the resonant circuit 210. The current sensor 70 provides the measured current value to a comparator 72. The comparator 72 accesses a preset threshold to determine whether the measured current value received from the current sensor 70 is outside the threshold range. Optionally, the comparator 72 determines whether the measured current is below the threshold. Optionally, the comparator 72 determines whether the measured current exceeds the threshold. Optionally, the comparator 72 determines whether the measured current is outside the threshold range. That is, the threshold can be a specific value (such as a value 10% higher or 10% lower than the normal current), or a range (such as within 10% of the normal current).

[0032] The preset threshold of the comparator 72 represents the expected amount of current drawn by the resonant circuit 210 during normal operation. When the current is outside the preset threshold range, the comparator 72 supplies an indication to the controller 68. This indication may notify the controller 68 that a metallic material is in proximity to the reader 12. In response to determining whether the current is above, below, or outside the preset value range, the controller 68 may detect that the resonant frequency of the inductive coupling reader has changed by an amount outside the threshold range. In such a case, the controller 68 activates a compensation circuit 220 to offset the change in the resonant frequency by coupling one or more capacitors in parallel with the resonant circuit 210.

[0033] As an example, the preset threshold value may be set to a value 10% higher or 10% lower than the value of the current drawn by the resonant circuit 210 (for example, the antenna of the resonant circuit 210) when there is no metal material in the vicinity of the reader 12. The preset threshold value may be programmed into a look-up table or memory at the time of manufacture of the reader 12, or may be dynamically updated based on various operating conditions, or both. The comparator 72 may read the preset threshold value from the look-up table or memory periodically or continuously and compare it with the current measured by the current sensor 70.

[0034] In some embodiments, after activating the compensation circuit 220, the controller 68 may instruct the current sensor 70 to re-measure the current drawn by the resonant circuit 210. By comparing the re-measured current with the preset threshold value by the comparator 72, it is determined whether the change in the resonant frequency of the resonant circuit 210 is still outside the threshold range. As an example, after activation of the compensation circuit 220, the current measured by the current sensor 70 may be within 5% of the normal operating current flowing through the resonant circuit 210. The preset threshold value may be set to a value 10% higher or lower than the normal operating current. In such a case, the controller 68 may determine that the change in the resonant frequency of the resonant circuit 210 is no longer outside the threshold range (for example, since the current measured by the current sensor 70 is neither more than 10% higher nor lower than the normal operating current of the resonant circuit 210).

[0035] In some embodiments, after activating the compensation circuit 220, the controller 68 may determine that the current measured by the current sensor 70 may be 12% higher than the normal operating current flowing through the resonant circuit 210. That is, even when the compensation circuit 220 is activated, the change in the resonant frequency of the resonant circuit 210 may still be outside the threshold range. In such a case, the controller 68 may instruct the compensation circuit 220 to couple one or more additional capacitors in parallel with the resonant circuit 210 (for example, to increase the total parallel capacitance coupled to the resonant circuit 210).

[0036] As an example, the compensation circuit 220 may include a first compensation circuit and a second compensation circuit. The first compensation circuit may include a first capacitor, and the second compensation circuit may include a second capacitor. The first capacitor may have the same size and value as the second capacitor. In such a case, the controller 68 determines that the change in the resonant frequency of the resonant circuit 210 is outside the range of the first threshold but within the range of the second threshold. For example, the first threshold may be set to a value 10% higher than the normal operating current drawn by the resonant circuit 210, and the second threshold may be set to a value 15% higher than the normal operating current drawn by the resonant circuit 210. The controller 68 may determine that the current drawn by the resonant circuit 210 is 12% higher than the normal operating current drawn by the resonant circuit 210. In such a case, the controller 68 determines that the change in the resonant frequency of the resonant circuit 210 is outside the range of the first threshold but within the range of the second threshold (as a result of the current drawn by the resonant circuit 210 being 12% higher than the normal operating current). In response, the controller 68 activates the first compensation circuit. By activating the first compensation circuit, the controller 68 couples the first capacitor in parallel with the resonant circuit 210.

[0037] In some cases, the controller 68 measures the current flowing through the resonant circuit 210 at some point after the activation of the first compensation circuit or before the first compensation circuit is activated. The controller 68 determines that the change in the resonant frequency is outside the range of the first threshold value and the second threshold value. For example, the controller 68 may determine that the current drawn by the resonant circuit 210 is 17% higher than the normal operating current drawn by the resonant circuit 210. In such a case, the controller 68 determines that the change in the resonant frequency of the resonant circuit 210 (as a result of the current drawn by the resonant circuit 210 being 17% higher than the normal operating current) is outside the range of the first threshold value (set, for example, to a value 10% higher than the normal operating current) and the second threshold value (set, for example, to a value 15% higher than the normal operating current). In response to this, the controller 68 activates the second compensation circuit. By activating the second compensation circuit, the controller 68 couples a first capacitor and a second capacitor in parallel with the resonant circuit 210.

[0038] In some embodiments, the first capacitor may be smaller than the second capacitor. In such a case, upon activation of the second compensation circuit, the larger capacitor is coupled in parallel with the resonant circuit 210, and the smaller capacitor of the first compensation circuit is separated from the resonant circuit 210. That is, if capacitors of different sizes are realized for each compensation circuit, only one of the first compensation circuit and the second compensation circuit is coupled to the resonant circuit 210.

[0039] In some embodiments, the first compensation circuit or the second compensation circuit is coupled in parallel with the resonant circuit 210 by a switch such as a transistor. For example, when the controller 68 activates (closes) the switch of the compensation circuit 220, one or more capacitors of the compensation circuit 220 may be coupled in parallel with the resonant circuit 210. When the switch is deactivated (opened), one or more capacitors are separated from the resonant circuit 210.

[0040] In some embodiments, the value of the capacitor or capacitance of the compensation circuit 220 is determined during the manufacture of the reader 12. In one example, for this purpose, the reader 12 is placed on a metal surface or metal material. Then, the detuning effect on the resonant circuit 210 of the reader 12 is measured. As an example, a current sensor may output a first current value drawn by the resonant circuit 210 when the reader 12 is not placed on a metal surface or metal material. This first current value may represent the expected current drawn by the resonant circuit 210 under normal operating conditions. In some cases, a threshold value may be calculated as a function or coefficient of this expected current (for example, the threshold value may be set to a value 10% higher than the first current value). In some cases, after the reader 12 is placed on a metal surface or metal material, the current sensor may output a second current value drawn by the resonant circuit 210. In such an embodiment, the threshold value may be set to the value of the second current value, or may be set to any value higher or lower than the second current value while being a function of the second current value. After the reader 12 is placed on the metal surface, one or more capacitors may be coupled in parallel with the resonant circuit 210 until a capacitor value that substantially brings the current measured by the current sensor closer to the first current value is determined. This capacitor value may be used to set the capacitor value of the compensation circuit 220. For this reason, when the reader 12 is operating in proximity to a metal surface (as determined, for example, by the current measured by the current sensor 70 exceeding the threshold value), the controller 68 activates the compensation circuit 220 and couples the capacitor value in parallel with the resonant circuit 210 to offset the change in the resonant frequency of the resonant circuit 210.

[0041] In some embodiments, the capacitor value can be determined mathematically (for example, without actually placing the reader 12 on a metal surface during manufacture). In some cases, the capacitor value can be determined based on the metal material on which the reader 12 will be set during operation.

[0042] FIG. 3 is a block diagram showing a reader unit used in an RFID system according to various embodiments. As shown in FIG. 3, the control circuit 68 may be coupled to a resonance circuit and a compensation circuit. The control circuit 68 may be implemented to include or may include or implement the functions of the controller 68. The control circuit 68 measures the current drawn by the resonance circuit. In response to a determination that the current drawn by the resonance circuit exceeds a threshold value, the controller 68 activates the switch 320. As a result, the compensation capacitor 310 is coupled in parallel with the resonance circuit. That is, the first terminal of the compensation capacitor 310 is grounded via the diode 330 and the switch 320. When the switch is released, the compensation capacitor 310 is no longer grounded and is thus separated from the resonance circuit. When the switch 320 is closed, the first terminal of the compensation capacitor 310 is grounded via the diode 330 and the switch 320. The second terminal of the compensation capacitor 310 is coupled to the first terminal of one or more capacitors of the resonance circuit. The second terminal of one or more capacitors of the resonance circuit is grounded. In this way, when the switch 320 is activated, i.e., closed, the compensation capacitor 310 can be coupled in parallel with the capacitor of the resonance circuit.

[0043] FIG. 4 is a flowchart showing an exemplary process 400 for operating an inductive coupling reader according to various embodiments. In operation 410, the inductive coupling reader detects a change in the resonance frequency of the inductive coupling reader.

[0044] In operation 420, the inductive coupling reader compares the change in the resonance frequency with a threshold value. In operation 430, the inductive coupling reader determines that the change in the resonance frequency is outside the range of the threshold value.

[0045] In operation 440, in response to determining that the change in the resonance frequency is outside the range of the threshold value, the inductive coupling reader activates a compensation circuit to offset the change in the resonance frequency of the inductive coupling reader.

[0046] FIG. 5 is a block diagram of an exemplary machine 500 that can execute any one or more of the techniques (e.g., methodologies) described herein, can be included in the above-described reader, or both. In alternative embodiments, machine 500 may operate as a stand-alone device or may be connected (e.g., networked) to other machines. In a networked configuration, machine 500 may operate in the capacity of a server machine, a client machine, or both in a server / client network environment. In one example, machine 500 may operate as a peer machine in a peer-to-peer (P2P) (or other distributed) network environment. Machine 500 may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a cellular phone, a web appliance, an IoT device, an automotive system, an aerospace system, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, although only a single machine is shown, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies described herein, such as cloud computing, software as a service (SaaS), or other computer cluster configurations.

[0047] As an example, as described in this specification, it may include or operate by logic, components, devices, packages, or mechanisms. The circuit configuration is an aggregate (e.g., a circuit set) of circuits embodied in a tangible object including hardware (e.g., simple circuits, gates, logic, etc.). The membership of the circuit configuration may be flexible depending on time and the underlying hardware variability. A plurality of circuits include a plurality of members that can perform specific tasks alone or in combination during operation. In one example, the hardware of the circuit configuration may be designed immutably (e.g., hardwired) to perform a specific operation. In one example, the hardware of the circuit configuration includes physical components of a variable connection (e.g., execution units, transistors, simple circuits, etc.) of a computer-readable medium in which physical changes (e.g., magnetic changes, electrical changes, changes by movable arrangements of invariant mass particles, etc.) have been made to encode instructions for a specific operation. In the connection of physical components, for example, from an insulator to a conductor (or vice versa), the electrical characteristics underlying the hardware configuration change. The instructions enable a part of a specific task to be executed during operation by having the involved hardware (e.g., an execution unit or a loading mechanism) generate members of the circuit configuration of the hardware by variable connection. Accordingly, the computer-readable medium is communicatively coupled to other components of the circuit during operation of the device. In one example, in two or more members of two or more circuit configurations, any of the physical components may be used. For example, during operation, an execution unit may be used by a first circuit of a first circuit configuration at one point in time and reused by a second circuit of the first circuit configuration or a third circuit of a second circuit configuration at another point in time.

[0048] A machine (e.g., a computer system) 500 may include a hardware processor 502 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof (such as a memory controller)), a main memory 504, and a static memory 506, and some or all of these may communicate with each other via an interconnect (e.g., a bus) 508. The machine 500 may further include a display device 510, an alphanumeric input device 512 (e.g., a keyboard), and a user interface (UI) navigation device 514 (e.g., a mouse). In one example, the display device 510, the alphanumeric input device 512, and the UI navigation device 514 may be a touch screen display. The machine 500 may further include a storage device 522 (e.g., a drive unit), a signal generating device 518 (e.g., a speaker), a network interface device 520, one or more sensors 516 (a Global Positioning System (GPS) sensor, a wing sensor, a mechanical element sensor, a temperature sensor, an ICP sensor, a bridge sensor, an audio sensor, an industrial sensor, a compass, an accelerometer, or other sensors, etc.), and one or more system-in-package data acquisition devices 590. The system-in-package data acquisition device 590 may implement some or all of the functions of the offset calibration system 100. The machine 500 may include an output controller 528 for communicating with or controlling one or more peripheral devices (e.g., a printer, a card reader, etc.), such as a serial (e.g., a universal serial bus (USB)), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection.

[0049] The memory device 522 may include a machine-readable medium storing one or more sets of data structures or instructions 524 (e.g., software) in which one or more implementations or uses of the techniques or functions described herein are made. Also, the instructions 524 may be, in whole or at least in part, in the main memory 504, in the static memory 506, or in the hardware processor 502 during execution by the machine 500. In one example, one or any combination of the hardware processor 502, the main memory 504, the static memory 506, and the memory device 521 may constitute a machine-readable medium.

[0050] Although the machine-readable medium is shown as a single medium, the term "machine-readable medium" may include a single medium configured to store one or more instructions 524, or may include multiple media (e.g., a centralized or distributed database or associated cache and server).

[0051] The term "machine-readable medium" can store, encode, or carry instructions for execution by machine 500, either temporarily or non-temporarily, and can be any temporary or non-temporary medium that causes machine 500 to execute any one or more of the technologies of the present disclosure, or can store, encode, or carry a data structure that is used by or associated with such instructions. Examples of non-limiting machine-readable media include solid-state memory as well as optical and magnetic media. In one example, a massive machine-readable medium includes a machine-readable medium with a plurality of particles having invariant (e.g., stationary) mass. Thus, a massive machine-readable medium is not a transient propagation signal. Specific examples of massive machine-readable media include non-volatile memories such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and CD-ROM and DVD-ROM disks, etc.

[0052] Command 524 (e.g., software, program, operating system (OS), etc.) or other data stored in storage device 521 can be used by hardware processor 502 through access by main memory 504. Main memory 504 (e.g., DRAM) is typically fast but volatile, and is a different type of storage from storage device 521 (e.g., SSD) which is suitable for long-term storage including the "off" state. Command 524 or data used by user or machine 500 is typically loaded into main memory 504 and used by hardware processor 502. When there is no space in main memory 504, main memory 504 can be supplemented by allocation of virtual space in storage device 521. However, storage device 521 is typically slower than main memory 504, and the write speed is typically at least twice slower than the read speed. Therefore, using virtual memory may significantly degrade the user experience due to the latency of the storage device (in contrast to main memory 504 (e.g., DRAM)). Furthermore, using storage device 521 for virtual memory purposes may significantly shorten the usable life of storage device 521.

[0053] Command 524 may further be transmitted or received on communication network 526 using a transmission medium via network interface device 520 that utilizes any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Exemplary communication networks include, among others, local area network (LAN), wide area network (WAN), packet data network (e.g., the Internet), mobile phone network (e.g., cellular network), plain old telephone service (POTS) network, and wireless data network (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard family (known as Wi-Fi (registered trademark)), IEEE 802.16 standard family (known as WiMax (registered trademark)), IEEE 802.15.4 standard family, peer-to-peer (P2P) network). In one example, network interface device 520 may comprise one or more physical jacks (e.g., Ethernet, coaxial, or telephone jacks) or one or more antennas for connecting to communication network 526.In one example, the network interface device 520 may include a plurality of antennas for performing wireless communication using single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) technology. The term "transmission medium" is considered to include any tangible or intangible medium that can store, encode, or carry instructions executed by the machine 500, including digital or analog communication signals or other tangible or intangible media that facilitate the communication of software as described above.

[0054] Each of the non-limiting aspects or examples described herein may stand on its own or may be combined in various permutations or combinations with one or more of the other examples.

[0055] In the above detailed description, reference has been made to the accompanying drawings, which form a part of the detailed description. The drawings illustrate, by way of example, specific embodiments in which the subject matter of the present invention may be realized. In this specification, these embodiments are also referred to as "examples". Such examples may include additional elements other than those illustrated or described. However, the inventors also contemplate examples in which only the elements illustrated or described are provided. Furthermore, the inventors contemplate examples (or one or more aspects thereof) that use any combination or permutation of the elements illustrated or described with respect to the specific examples (or one or more aspects thereof) illustrated or described herein or other examples (or one or more aspects thereof).

[0056] If there is a conflict between this specification and any document incorporated by reference, the usage of this specification shall prevail. In this book, the term "one (of)" is used to include one or more, independent of any other instances or uses of "at least one" or "one or more", as is common in patent documents. In this book, "or (or)" is used to mean non-exclusive, so "A or B" includes, unless otherwise indicated, "A but not B", "B but not A", and "A and B". In this book, "comprising" and "in which" are used as the plain English equivalents of the terms "including" and "wherein", respectively. Also, in the following claims, "including" and "comprising" are non-limiting, i.e., a system, device, product, composition, design, or process that includes elements other than those recited after such terms in the claim is still considered to be within the scope of that claim. Also, in the following claims, terms such as "first", "second", and "third" are used merely as labels and are not intended to impose numerical requirements on them.

[0057] Examples of the methods described herein may be implemented, at least in part, by a machine or computer. Some examples may include a computer-readable medium or a machine-readable medium encoded with transient or non-transient instructions operable to configure an electronic device to implement the methods described in the above examples. Embodiments of such methods may include code such as microcode, assembly language code, high-level language code, etc. The code may include transient or non-transient computer-readable instructions for implementing various methods. The code may form part of a computer program product. Further, in one example, the code may be tangibly stored on one or more volatile non-transient, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or memory sticks, random access memory (RAM), read-only memory (ROM), etc.

[0058] The foregoing description is not restrictive, but is intended to be exemplary. For example, the above examples (or one or more aspects thereof) may be used in combination with each other. In considering the foregoing description, other examples may be used, for example, by those of ordinary skill in the art. The abstract is provided in accordance with 37 C.F.R. § 1.72(b) to enable the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above detailed description, various features may be grouped together in order to simplify the disclosure. This should not be interpreted as intending that features which are not claimed but are disclosed are essential to any of the claims. Rather, the subject matter of the invention may not necessarily lie in all of the features of a particular disclosed embodiment. Accordingly, the following claims are hereby incorporated by reference as examples or embodiments into the detailed description, and each claim stands on its own as a separate embodiment, and the embodiments are contemplated to be combinable with each other in various combinations or permutations. The scope of the subject matter of the present invention should be determined with reference to the appended claims, along with the full scope of equivalents to which the claims are entitled.

Claims

1. 1. A system comprising: an inductively coupled reader arranged to interrogate in a coverage area of ​​the inductively coupled reader to detect the presence of one or more RF tags within said coverage area; The inductive coupling reader comprises: a resonant circuit comprising a receiver for receiving, demodulating and decoding an identification signal from the one or more RF tags within the coverage area; A compensation circuit; one or more processors configured to perform a plurality of operations; The plurality of operations include: detecting a change in a resonant frequency of the resonant circuit; comparing the change in the resonant frequency to a threshold based on comparing an amount of current being applied to the resonant circuit with an expected amount of current; determining that the change in the resonant frequency is outside the threshold range based on determining that the amount of current being conducted through the resonant circuit is greater or less than the expected amount of current by a given amount; in response to detecting the change in the resonant frequency and determining that the change in the resonant frequency is outside the threshold range, activating the compensation circuit to offset the change in the resonant frequency of the inductively coupled reader; receiving from the receiver the one or more identification signals corresponding to the one or more RF tags within the coverage area.

2. 2. The system of claim 1, wherein the change in the resonant frequency is caused by an external metallic material in proximity to the inductively coupled reader, and wherein a range of the inductively coupled reader is reduced as a result of the change in the resonant frequency.

3. The compensation circuit includes: Switch, and one or more capacitors having a first terminal coupled to a first terminal of a capacitor of a resonant circuit of the inductively coupled reader and a second terminal coupled to the switch.

4. The compensation circuit includes a first compensation sub-circuit, and the one or more processors: activating the first compensation sub-circuit in response to determining that the change in the resonant frequency is outside the threshold range and within a second threshold range; activating a second compensation subcircuit in response to determining that the change in the resonant frequency is outside the threshold and the second threshold, the second compensation subcircuit applying a larger offset to the resonant frequency than the first compensation subcircuit.

5. 5. The system of claim 4, wherein activation of the first compensation sub-circuit couples a first capacitor in parallel with the resonant circuit and activation of the second compensation sub-circuit couples a second capacitor in parallel with the resonant circuit, the second capacitor being larger than the first capacitor.

6. The system of claim 5 , wherein the second capacitor comprises the first capacitor and at least one other capacitor.

7. a current sensor coupled to the resonant circuit for measuring an amount of current flowing through the resonant circuit; 10. The system of claim 1, further comprising a comparator that determines whether a measured amount of current being passed through the resonant circuit exceeds a stored threshold.

8. The system of claim 7 , wherein the stored thresholds are stored in a programmed look-up table.

9. The system of claim 7 , wherein the processor is further configured to dynamically update the stored threshold value.

10. 8. The system of claim 7, wherein the stored thresholds include a lower threshold and an upper threshold, and the processor is further configured to detect the change in the resonant frequency by determining whether a current being passed through the resonant circuit does not exceed the lower threshold or exceeds the upper threshold.

11. The compensation circuit includes: a first compensation sub-circuit including a first capacitor and a second compensation sub-circuit including a second capacitor; The one or more processors: re-determining the current flowing through the resonant circuit after activation of the first compensation sub-circuit; in response to determining that the redetermined current through the resonant circuit still exceeds the threshold, activating the second compensation sub-circuit; 2. The system of claim 1, wherein activation of the first compensation sub-circuit couples the first capacitor in parallel with the resonant circuit and activation of the second compensation sub-circuit couples the second capacitor in parallel with the resonant circuit.

12. The resonant circuit includes a transmitter, and the one or more processors: The system of claim 1 , further configured to perform a number of actions including generating an alert signal with the transmitter.

13. The resonant circuit includes a transmitter, and the one or more processors: The system of claim 1 , further configured to perform a number of actions including generating a confirmation signal with the transmitter.

14. 1. A method for operating an inductively coupled reader, comprising: detecting a change in a resonant frequency of the inductively coupled reader; comparing the change in resonant frequency to a threshold based on comparing an amount of current being applied to the inductively coupled reader to an expected amount of current; determining that the change in resonant frequency is outside the threshold range based on determining that the amount of current being applied to the inductively coupled reader is greater or less than the expected amount of current by a given amount; in response to determining that the change in the resonant frequency is outside the threshold range, activating a first compensation subcircuit to offset the change in the resonant frequency of the inductively coupled reader; re-detecting the change in the resonant frequency of the inductive coupling reader by determining an amount of current being passed through the inductive coupling reader after activation of the first compensation sub-circuit; re-determining that the change in the resonant frequency is outside the threshold range based on determining that the amount of current being passed through the inductively coupled reader after activation of the first compensation sub-circuit remains greater than or less than the expected amount of current by a given amount; in response to again determining that the change in the resonant frequency is still outside the threshold range, activating a second compensation sub-circuit to offset the change in the resonant frequency of the inductively coupled reader.

15. 1. A method for operating an inductively coupled reader, comprising: detecting a change in a resonant frequency of the inductively coupled reader; comparing the change in resonant frequency to a threshold based on comparing an amount of current being applied to the inductively coupled reader to an expected amount of current; determining that the change in resonant frequency is outside the threshold range based on determining that the amount of current being applied to the inductively coupled reader is greater or less than the expected amount of current by a given amount; in response to determining that the change in the resonant frequency is outside the threshold range, adjusting a capacitance of a switchable tuning capacitor based on an amount of additional parallel capacitance needed to offset the change in the resonant frequency, and coupling the switchable tuning capacitor to offset the change in the resonant frequency of the inductively coupled reader.

16. re-detecting the change in the resonant frequency of the inductive coupling reader by re-determining the amount of current being passed through the inductive coupling reader after coupling the switchable tuning capacitor; re-determining that the re-determined current through the inductive coupling reader still exceeds the threshold; 16. The method of claim 15, further comprising, in response to re-determining that the change in the resonant frequency is still outside the threshold range, readjusting the capacitance of the switchable tuning capacitor based on an additional amount of parallel capacitance needed to further mitigate and compensate for the change in the resonant frequency of the inductively coupled reader.

17. The method of claim 15 , further comprising reading the threshold value from a memory.

18. The method of claim 15 , further comprising retrieving the threshold value from a lookup table.

19. The method of claim 18 , wherein the retrieval of the threshold value is performed periodically.

20. The method of claim 18 , wherein the reading of the threshold value is performed continuously.

21. The method of claim 18 , further comprising dynamically updating the threshold value based on one or more operating conditions.

22. an inductively coupled reader arranged to interrogate in a coverage area of ​​the inductively coupled reader to detect the presence of one or more RF tags within said coverage area, said inductively coupled reader comprising: A resonant circuit comprising: a transmitter for transmitting a signal within the coverage area; a receiver for receiving, demodulating and decoding an identification signal from the one or more RF tags within the coverage area; a current sensor coupled to the resonant circuit for measuring an amount of current flowing through the resonant circuit; A compensation circuit; one or more processors configured to perform a number of operations; The plurality of operations include: receiving a current measurement from the current sensor corresponding to an amount of current being conducted through the resonant circuit; Reading a stored threshold value determined based on a defined difference that is greater or less than the expected current amount by a given amount; comparing the current measurements to the stored thresholds to assess a change in resonant frequency of the inductively coupled reader; determining whether the current measurement is outside the stored threshold range; in response to determining that the current measurement is outside the threshold range, activating the compensation circuit to offset the change in the resonant frequency of the inductively coupled reader; receiving from the receiver the one or more identification signals corresponding to the one or more RF tags within the coverage area.

23. 23. The inductively coupled reader of claim 22, further comprising an antenna and a matching and tuning circuit for compensating and matching the impedance of the antenna.

24. an inductively coupled reader arranged to interrogate in a coverage area of ​​the inductively coupled reader to detect the presence of one or more RF tags within said coverage area, said inductively coupled reader comprising: A resonant circuit comprising: a transmitter for transmitting a signal within the coverage area; a receiver for receiving, demodulating and decoding an identification signal from the one or more RF tags within the coverage area; a current sensor coupled to the resonant circuit for measuring an amount of current flowing through the resonant circuit; A compensation circuit; a comparator coupled to the current sensor and configured to perform a plurality of operations, the plurality of operations including: receiving a current measurement from the current sensor corresponding to an amount of current being conducted through the resonant circuit; reading a stored threshold value indicative of a predetermined difference greater or less than a given amount of expected current drawn by the resonant circuit; and comparing a change in resonant frequency based on comparing the current measurement to the stored threshold value. One or more processors configured to perform a plurality of operations, the plurality of operations including: obtaining an indication from the comparator that the change in resonant frequency exceeds the stored threshold; in response to determining that the given amount of change is outside of the threshold range, activating the compensation circuit to offset the change in the resonant frequency of the inductively coupled reader; and receiving from the receiver the one or more identification signals corresponding to the one or more RF tags within the coverage area.

25. an inductively coupled reader arranged to interrogate in a coverage area of ​​the inductively coupled reader to detect the presence of one or more RF tags within said coverage area, said inductively coupled reader comprising: A resonant circuit comprising: a transmitter for transmitting a signal within the coverage area; a receiver for receiving, demodulating and decoding an identification signal from the one or more RF tags within the coverage area; a current sensor coupled to the resonant circuit for measuring an amount of current flowing through the resonant circuit; a switchable tuning capacitor; a comparator coupled to the current sensor and configured to perform a plurality of operations, the plurality of operations including: receiving a current measurement from the current sensor corresponding to an amount of current being conducted through the resonant circuit; retrieving a stored threshold value indicative of a predetermined difference greater or less than a given amount of expected current drawn by the resonant circuit; and comparing a change in resonant frequency based on comparing the current measurement to the stored threshold value. One or more processors configured to perform a plurality of operations, the plurality of operations including: obtaining an indication from the comparator that the change in resonant frequency exceeds the stored threshold; in response to determining that the given amount of change is outside of the threshold range, adjusting a capacitance of the switchable tuning capacitor based on an amount of additional parallel capacitance needed to mitigate and compensate for the change in the resonant frequency and coupling the switchable tuning capacitor to offset the change in the resonant frequency of the inductively coupled reader; and receiving from the receiver the one or more identification signals corresponding to the one or more RF tags within the coverage area.

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