Dynamic frequency tuning in inductively coupled system

Abstract

To improve the overall power efficiency and range of an inductively coupled reader.SOLUTION: The present disclosure describes techniques for operating an inductively coupled reader. The technique includes the operations of: applying an excitation frequency to a resonant circuit of the inductively coupled reader; detecting a change in a resonant frequency of the resonant circuit of the inductively coupled reader; and adjusting the excitation frequency applied to the resonant circuit in response to detection of a change in the resonant frequency of the inductively coupled reader.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] This specification generally relates to radio frequency identification (RFID) systems, and more specifically to techniques for reducing harmful interference effects in RFID systems, although not limited thereto. This application claims priority to U.S. Provisional Application No. 16 / 705,574, filed on December 6, 2019, the entire disclosure of which is incorporated herein by reference.

Background Art

[0002] An RFID system is a system that uses radio frequency transponders (e.g., tags) to identify items of interest. Each radio frequency transponder is attached to or near a corresponding item and contains information identifying that item. When identification is needed, a radio frequency reader unit (e.g., interrogator) is used to excite (e.g., interrogate) the transponder on the item, and an identification signal (including the identification information of the item) is returned to the reader unit. The reader unit uses the identification information received from the transponder to perform any of various RFID applications. For example, the identification information can be used to perform functions such as asset management, inventory tracking, access control, and the like.

Summary of the Invention

[0003] In some particular embodiments, a system and method for operating an inductively coupled reader are provided. The systems and methods of the present disclosure perform operations including applying an excitation frequency to a resonant circuit of the inductively coupled reader, detecting a change in a resonant frequency of the resonant circuit of the inductively coupled reader, and adjusting the excitation frequency applied to the resonant circuit in response to detecting the change in the resonant frequency of the inductively coupled reader.

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

[0005] In some embodiments, detecting the change includes accessing configuration information of the inductive coupling reader that indicates that the inductive coupling reader is in proximity to an external metal material.

[0006] In some embodiments, the resonant circuit includes a tuned oscillator configured to generate a constant resonance frequency of 125 kHz or 134 kHz. In some embodiments, the operation includes applying a first excitation frequency to the resonant circuit of the inductive coupling reader, measuring a first amplitude of a first voltage that occurs between both ends of the resonant circuit of the inductive coupling reader by applying the first excitation frequency, and determining that the first amplitude of the first voltage does not meet a criterion.

[0007] In some embodiments, the criterion includes a predetermined voltage level. In some embodiments, the criterion includes exceeding a voltage level generated by applying a second excitation frequency.

[0008] In some embodiments, the operation includes applying a second excitation frequency to the resonant circuit of the inductive coupling reader, measuring a second amplitude of a second voltage that occurs between both ends of the resonant circuit of the inductive coupling reader by applying the second excitation frequency, and determining that the first amplitude of the first voltage is smaller than the second amplitude of the second voltage.

[0009] In some embodiments, adjusting the excitation frequency applied to the resonant circuit includes setting the excitation frequency to the second excitation frequency. In some embodiments, the second excitation frequency is higher or lower than the first excitation frequency by a predetermined value.

[0010] In some embodiments, the operation includes operating an inductively coupled device inductively coupled to the inductive coupling reader at the adjusted excitation frequency, and the inductively coupled device derives a clock frequency from the adjusted excitation frequency such that data transfer between the inductively coupled device and the inductive coupling reader is synchronized with the adjusted excitation frequency.

[0011] In some embodiments, the inductively coupled device includes a radio frequency identification (RFID) authentication device. In some embodiments, the inductive coupling reader includes a radio frequency identification (RFID) reader.

[0012] In some embodiments, the adjusted value of the excitation frequency is determined by applying a range of frequencies to the resonant circuit and identifying the frequency at which the maximum voltage amplitude occurs at the output of the inductive coupling reader.

[0013] When a metal material is in proximity to a conventional RFID reader, the resonant frequency of the resonant circuit of the RFID reader changes due to the metal material, and thus the range of the conventional RFID reader is usually reduced by the metal material. The disclosed embodiments detect interference such as caused by the metal material and, in response, adjust the excitation (drive) frequency applied to the resonant circuit. Thereby, the overall power efficiency and range of the disclosed RFID reader are improved over conventional RFID readers.

[0014] This summary is intended to provide an overview of the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive explanation of the subject matter of the present invention. The detailed description is included to provide further information regarding this patent application.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

[0016] The drawings are not necessarily drawn to scale, and like reference numerals in the drawings may represent like components from different perspectives. Like reference numerals with different suffixes may represent different examples of like components. The drawings generally illustrate, by way of example and not limitation, the various embodiments described herein.

[0017] The present disclosure describes techniques for operating an inductive coupling reader in particular. Specifically, the techniques of the present disclosure detect interference and detuning of the resonant circuit of the inductive coupling reader and, in response thereto, adjust the excitation (drive) frequency applied to the resonant circuit. Thereby, the overall power efficiency and range of an inductive coupling reader such as an RFID reader are improved, thereby improving the overall efficiency and functionality of the computer.

[0018] In an RFID system, problems occur when one or more external interference signals are present within the system's frequency band during an interrogation operation. Such interference can cause misidentification and false reporting of items of interest in the RFID system. Such interference becomes more likely to be caused by metal materials located near the system of interest. Such metal materials significantly reduce the range of the RFID interrogator, especially by changing the resonant frequency of the resonant circuit of the RFID interrogator. For example, when an inductively coupled reader (e.g., a 13.56 MHz RFID reader) is attached to a metal surface, the apparent inductance of the antenna changes. 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), detuning of this circuit causes a decrease in actual performance (e.g., read range), especially because the drive frequency does not match the resonant frequency of the antenna. As a result, the RFID reader consumes more power to read a given RFID tag, wasting system resources.

[0019] To address the problems of such typical situations, the technology of the present disclosure detects a situation where the resonant circuit of an inductively coupled reader is detuned and compensates for such detuning by changing the excitation (drive) frequency applied to the resonant circuit. Thereby, the performance of the inductively coupled reader can be restored and improved, so that the power efficiency and range of the inductively coupled reader are improved. As a result, the overall efficiency and functionality of the computer are improved.

[0020] 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 plurality of RF identification tags 16, 18, 20, 22, 24, 26, and the RF identification tags 16, 18, 20, 22, 24, 26 are each attached to a corresponding item of interest 34, 36, 38, 40, 42, 44 and used to identify that item of interest. Items of interest 34, 36, 38, 40, 42, 44 can include, for example, inventory pieces, people, capital assets, animals, or any other object that may desirably be tracked or monitored within a particular area. The number of items that can be tracked by a particular reader is typically a matter of design choice.

[0021] The RF reader unit 12 can be, for example, a fixed unit such as a proximity reader mounted on a wall or a portable unit that can be easily repositioned. Generally, the coverage area served by an RF reader unit can depend on the transmission power level of that reader, the antenna pattern of the reader transmission antenna, and the position and orientation of that reader at any given time.

[0022] During normal operation of the exemplary system of FIG. 1, the RF reader unit 12 periodically interrogates its coverage area 52 to identify the item of interest currently located therein. That is, the reader unit 12 periodically transmits an RF interrogation signal within the coverage area 52, and this interrogation signal functions as a "request" for each of the RF identification tags 16-26 within the area 52, causing the transmission of an identification signal that identifies the associated item of interest. The RF interrogation signal drives the resonant circuit at a specific frequency that matches the resonant frequency of the resonant circuit. When the RF tag receives the RF interrogation signal, it derives a local clock frequency based on the RF interrogation signal. The RF tag synchronizes the transmission and reception of data with the reader unit 12 according to the local clock frequency and thus the drive frequency of the RF interrogation signal. Each RF tag within the coverage area 52 responds by receiving the interrogation signal and returning its identification signal to the interrogating reader. After receiving identification information from all the RF tags within the coverage area 52, the RF reader unit reports the collected information to the appropriate entity.

[0023] Referring to FIG. 1, it can be understood that interference is likely to occur between the RF reader unit 12 and the metal material. For example, the RF reader unit 12 can be attached to a wall containing a 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 item in the region 52 farther away from the RF reader unit 12. In particular, while the resonant frequency of the resonant circuit changes, the drive frequency of the interrogation signal can correspond to the resonant frequency expected under conditions where there is no interference. Since the drive frequency and the resonant frequency do not match, the overall power consumed by the system increases and the range of the RF reader unit 12 decreases. That is, the size of the region 52 can decrease when a metal material is present near the RF reader unit 12. Also, since the resonant frequency of the RF reader unit 12 changes, the amount of power required for the RF reader unit 12 to operate properly can increase.

[0024] According to the present disclosure, there are provided a method and an apparatus for reducing the adverse effects of interference in an RFID system by changing the excitation (drive) frequency applied to a resonant circuit to compensate when it is determined that a metal material causes a change in the resonant frequency of the RF reader unit 12.

[0025] FIG. 2A is a block diagram showing an RF reader unit 200 according to an embodiment of the present disclosure. The RF reader unit 200 can be an example of the RF reader unit 12 (FIG. 1). As shown, the reader unit 200 can include a tuning circuit 210, a driver circuit 230, a receiver circuit 240, an antenna voltage detection circuit 250, and a microcontroller 220. In some implementations, the antenna voltage detection circuit 250 can be excluded or deactivated from the RF reader unit 200.

[0026] The microcontroller 220 is operable to control the operation of the RF reader unit 200 to query, track, and report on items of interest within the coverage area 52 of the RF reader unit 200. The microcontroller 220 is implemented using a digital processing device such as a general-purpose microprocessor, digital signal processor, reduced instruction set computer, complex instruction set computer, or field programmable gate array. Further, one or more of the other functional blocks shown in FIG. 2A may be digitally implemented within the same (or different) digital processor as the microcontroller 220. The microcontroller 220 may include an adjustable frequency timer and volatile and non-volatile memory.

[0027] The tuning circuit 210 includes an inductive loop antenna and a tuning capacitor. The tuning circuit 210 is used to generate and transmit (under the control of the microcontroller 220 and the driver circuit 230) interrogation signals for transmission into the coverage area 52 via the inductive loop antenna during an interrogation operation. The receiver circuit 240 operates to receive, among other things, identification signals from RF tags located within the coverage area 52, demodulate and decode the received identification signals, and supply the resulting identification information to the microcontroller 220.

[0028] In some embodiments, the microcontroller 220 detects a change in the resonance frequency of the RF reader unit 200. Specifically, the microcontroller 220 detects a change in the resonance frequency of the tuning circuit 210. In some implementations, the microcontroller 220 detects a change in the resonance frequency based on a preset setting value of the microcontroller 220 stored in the non-volatile memory of the microcontroller 220. For example, during operation or manufacturing of the RF reader unit 200, the configuration bits stored in the non-volatile memory of the microcontroller 220 may indicate the presence or absence of an interference source such as a metal material. The microcontroller 220 can determine whether the configuration bit is asserted or de-asserted by accessing the configuration bit during operation. If the configuration bit is asserted, the microcontroller 220 determines that an interference source such as a metal material is present or is near the RF reader unit 200. In such a case, the microcontroller 220 detects a change in the resonance frequency of the RF reader unit 200. If the configuration bit is de-asserted, the microcontroller 220 determines that no interference source is present.

[0029] In some embodiments, the microcontroller 220 communicates with the antenna voltage detection circuit 250 to determine and detect changes in the resonance frequency of the RF reader unit 200. Specifically, the microcontroller 220 can use the antenna voltage detection circuit 250 to measure the value of the voltage consumed by the tuning circuit 210 when an interrogation signal having a given excitation frequency is applied to the tuning circuit 210. The given excitation frequency applied is a frequency that matches the expected resonance frequency of the tuning circuit 210 (e.g., the resonance frequency at which the tuning circuit 210 normally operates when there is no interference source). For example, the tuning circuit 210 can be configured to operate at a resonance frequency of 125 kHz or 134 kHz or any other suitable value. In such a case, the excitation frequency of the interrogation signal is also set to 125 kHz or 134 kHz to match the resonance frequency. If the voltage value does not meet or falls below a specific threshold (e.g., because the resonance frequency does not match the excitation frequency), the microcontroller 220 detects the change in the resonance frequency.

[0030] When it is determined that the resonance frequency of the tuning circuit 210 has changed, the microcontroller 220 cancels the change in the resonance frequency by adjusting the excitation frequency of the interrogation signal using an adjustable frequency timer. For example, if the resonance frequency is 10% higher than the expected resonance frequency, the microcontroller 220 increases the excitation frequency by 10%.

[0031] The preset threshold value against which the voltage measured by the antenna voltage detection circuit 250 is compared can be set 10% (or any other suitable ratio or value) higher or 10% (or any other suitable ratio or value) lower than the value of the voltage consumed by the tuning circuit 210 when no metal material is in proximity to the RF reader unit 200. The preset threshold value can be programmed into a look-up table or memory during the manufacture of the RF reader unit 200 and / or can be dynamically updated based on different operating conditions. In some cases, the preset threshold value may be a specific value or a range of values. When the measured voltage is outside the range of values, the microcontroller 220 detects the change in the resonance frequency and adjusts the excitation frequency of the interrogation circuit to a specific value.

[0032] In some cases, the microcontroller 220 instructs the driver circuit 230 to operate at a first frequency or a second frequency. The first frequency may correspond to the resonance frequency of the tuning circuit 210 under normal conditions where no interference source is present. In response to detecting a change in the resonance frequency (e.g., based on configuration bit values or the measured voltage), the microcontroller 220 instructs the driver circuit 230 to operate at a second frequency that is higher or lower than the first frequency.

[0033] In some embodiments, the microcontroller 220 searches for the optimal excitation frequency of the interrogation signal based on the voltage value measured by the antenna voltage detection circuit 250. For example, the microcontroller 220 may first drive the tuning circuit 210 at a first frequency corresponding to the resonance frequency of the tuning circuit 210 under normal conditions where there is no interference source. The microcontroller 220 receives a first voltage measurement value from the antenna voltage detection circuit 250. The microcontroller 220 stores this first voltage measurement value in the volatile memory of the microcontroller 220. Next, the microcontroller 220 increases the excitation frequency and drives the tuning circuit 210 at a second frequency higher than the first frequency. The microcontroller 220 receives a second voltage measurement value from the antenna voltage detection circuit 250. The microcontroller 220 compares the second voltage measurement value with the first voltage measurement value. In response to determining that the second voltage measurement value is greater than the first voltage measurement value, the microcontroller 220 may increase the excitation frequency and drive the tuning circuit 210 at a third frequency higher than the second frequency. Alternatively, in response to determining that the second voltage measurement value is greater than the first voltage measurement value, the microcontroller 220 may set the excitation frequency to drive the tuning circuit 210 at the second frequency. In response to determining that the second voltage measurement value is less than the first voltage measurement value, the microcontroller 220 may decrease the excitation frequency and drive the tuning circuit 210 at a third frequency lower than the first frequency. Alternatively, in response to determining that the second voltage measurement value is less than the first voltage measurement value, the microcontroller 220 may set the excitation frequency to drive the tuning circuit 210 at the first frequency.

[0034] The microcontroller 220 compares again the voltage obtained as a result measured by the antenna voltage detection circuit 250 when driving the tuning circuit 210 at a third frequency with the voltage obtained when driving the tuning circuit 210 at a previous frequency. If the third frequency corresponds to a frequency higher than the previously applied frequency, the microcontroller 220 may continue to gradually increase the driving frequency by a specific value until the resulting voltage becomes lower than the previously measured voltage. If the third frequency corresponds to a frequency lower than the previously applied frequency, the microcontroller 220 may continue to gradually decrease the driving frequency by a specific value until the resulting voltage becomes lower than the previously measured voltage. At that point, the microcontroller 220 sets the driving frequency to the frequency that brought about the previously measured voltage. That is, the microcontroller 220 searches for (by gradually increasing or decreasing the driving frequency) the frequency that brings about the maximum voltage measurement value output by the antenna voltage detection circuit 250.

[0035] Figure 2B is a waveform of the drive frequency versus the resonance frequency of an exemplary RFID system according to various embodiments. As shown in Figure 2B, when the drive frequency of the interrogation signal applied to the resonance circuit does not match the resonance frequency of the resonance circuit, the antenna voltage (and thus the range of the RFID system) decreases. As shown in Figure 2B, the antenna voltage reaches a maximum value when the drive frequency matches the resonance or resonant frequency of the resonance circuit. Specifically, under normal operating conditions where there is no interference source such as a metal material or the interference source is not close to the RF reader unit 200, the resonance frequency of the resonance circuit is a preset value of 125 kHz or 134 kHz. The excitation frequency of the interrogation signal applied to the resonance circuit is also 125 kHz or 134 kHz, and the excitation frequency is set to be equal to or match the value of the resonance frequency. The voltage obtained as a result of the measurement by the antenna voltage detection circuit 250 is close to or at the maximum value. At a later point in time, when the RF reader unit 200 is placed very close to an interference source such as a metal material, the resonance frequency of the resonance circuit changes (e.g., from 125 kHz to 135 kHz). Driving the resonance circuit at the currently set excitation frequency (e.g., 125 kHz) causes the voltage measurement value provided by the antenna voltage detection circuit 250 to decrease compared to the previously measured maximum voltage value. In response, the excitation frequency is increased or decreased to a specific value that can match the changed resonance frequency of the resonance circuit. As a result, when driving the resonance circuit at the adjusted excitation frequency (e.g., 135 kHz), the voltage measurement value provided by the antenna voltage detection circuit 250 becomes close to or equal to the maximum value.

[0036] In this case, the inductive coupling device (e.g., the RF tag) receives the RF interrogation signal at the adjusted excitation frequency and derives the local clock frequency based on the RF interrogation signal (e.g., 135 kHz). The inductive coupling device synchronizes the transmission and reception of data with the reader unit 12 according to the local clock frequency and thus the adjusted excitation (drive) frequency of the RF interrogation signal.

[0037] FIG. 3 is a flowchart illustrating an exemplary process 300 for operating an inductive coupling reader according to various embodiments. In operation 310, the inductive coupling reader applies an excitation frequency to a resonant circuit of the inductive coupling reader.

[0038] In operation 320, the inductive coupling reader detects a change in a resonant frequency of the resonant circuit of the inductive coupling reader. In operation 330, the inductive coupling reader adjusts the excitation frequency applied to the resonant circuit in response to detecting a change in the resonant frequency of the inductive coupling reader.

[0039] FIG. 4 is a block diagram of an exemplary machine 400 on which any one or more of the techniques (e.g., methods) described herein may be performed and / or may be included as part of an inductive coupling reader. In alternative embodiments, machine 400 may operate as a stand-alone device or may be connected (e.g., networked) to other machines. In a network deployment, machine 400 may operate in the server-client network environment as a server machine, a client machine, or both. In one example, machine 400 may function as a peer machine in a peer-to-peer (P2P) (or other distributed) network environment. Machine 400 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) specifying actions to be taken by that machine. Further, although only a single machine is illustrated, the term "machine" shall be construed 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 methods described herein, such as via cloud computing, software as a service (SaaS), or other computer cluster configurations.

[0040] Examples described herein may include or be operated by logic, components, devices, packages, or mechanisms. A circuit configuration is a group (e.g., a set) of circuits implemented in a tangible entity that includes hardware (e.g., simple circuits, gates, logic, etc.). Circuit components can flexibly adapt to the passage of time and fluctuations in the underlying hardware. A circuit includes elements that can perform specific tasks either alone or in cooperation during operation. In one example, the hardware of a circuit configuration can be fixedly designed to perform a specific operation (e.g., something incorporated into the hardware). In one example, the hardware of a circuit configuration can include a physically (e.g., magnetically, electrically, or by the movable arrangement of invariant mass particles) changeable computer-readable medium for encoding instructions for a specific operation, and variably connected physical components (e.g., execution units, transistors, simple circuits, etc.). When connecting physical components, the underlying electrical characteristics of the hardware components are changed (e.g., from an insulator to a conductor or vice versa). Instructions enable the constituent hardware (e.g., execution units and loading mechanisms) to form elements of the circuit configuration within the hardware via variable connections and perform part of a specific task during operation. Thus, the computer-readable medium is communicatively coupled to other components of the circuit configuration when the device is operating. In one example, any of the physical components can be used by multiple elements of multiple circuit configurations. For example, during operation, an execution unit can be used by a first circuit in a first circuit configuration at one point in time and reused by a second circuit in the first circuit configuration or by a third circuit in a second circuit configuration at another point in time.

[0041] A machine (e.g., a computer system) 400 can include a hardware processor 402 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof, e.g., a memory controller, etc.), a main memory 404, and a static memory 406. Some or all of these can communicate with each other via an interconnect (e.g., a bus) 408. The machine 400 can further include a display device 410, an alphanumeric input device 412 (e.g., a keyboard), and a user interface (UI) navigation device 414 (e.g., a mouse). In one example, the display device 410, the alphanumeric input device 412, and the UI navigation device 414 can be a touch screen display. The machine 400 can further include a storage device 422 (e.g., a drive unit), a signal generation device 418 (e.g., a speaker), a network interface device 420, and one or more sensors 416 (e.g., a global positioning system (GPS) sensor, a wing sensor, a mechanical device sensor, a temperature sensor, an ICP sensor, a bridge sensor, an audio sensor, an industrial sensor, a compass, an accelerometer, or other sensors, etc.). The machine 400 can include an output controller 428 (e.g., a serial connection (e.g., a universal serial bus (USB)), a parallel connection, or other wired or wireless (e.g., infrared (IR)) connection, a near field communication (NFC) connection, etc.) for communicating with or controlling one or more peripheral devices (e.g., a printer, a card reader, etc.).

[0042] Storage device 422 may include a machine-readable medium storing one or more sets of data structures or instructions 424 (e.g., software) that embody or utilize any one or more of the techniques or functions described herein. Also, the instructions 424 may be present, in whole or at least in part, within main memory 404, within static memory 406, or within hardware processor 402 during execution of instructions 424 by machine 400. In one example, the machine-readable medium may be constituted by one of hardware processor 402, main memory 404, static memory 406, and storage device 421 or any combination thereof.

[0043] Although the machine-readable medium is shown as a single medium, the term "machine-readable medium" may include a single medium or a plurality of media (e.g., a centralized or distributed database, or associated caches and servers) configured to store one or more instructions 424.

[0044] The term "machine-readable medium" includes a transient or non-transient medium capable of storing, encoding, or carrying transient or non-transient instructions for execution by machine 400, and capable of storing, encoding, or carrying data structures used by or associated with such instructions to cause machine 400 to execute any one or more of the techniques of this disclosure. Non-limiting examples of machine-readable media include solid state memories, optical media, and magnetic media. In one example, a mass machine-readable medium includes a machine-readable medium having a plurality of particles with invariant (e.g., stationary) mass. Thus, a mass machine-readable medium is not a transient propagation signal. Specific examples of mass machine-readable media can include non-volatile memories such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable and programmable read-only memory (EEPROM)), flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, CD-ROM disks, and DVD-ROM disks.

[0045] Instructions 424 (e.g., software, programs, operating systems (OS), etc.) or other data stored in storage device 421 can be accessed by main memory 404 for use by hardware processor 402. Main memory 404 (e.g., DRAM) is typically fast but volatile, and thus is a different type of storage than storage device 421 (e.g., SSD) which is suitable for long-term storage including periods in the "off" state. When used by the user or machine 400, instructions 424 or data are typically loaded into main memory 404 for use by hardware processor 402. When main memory 404 becomes full, virtual space from storage device 421 can be allocated to supplement main memory 404, but storage device 421 is typically slower than main memory 404 and the write speed is typically at least twice as slow as the read speed, so the use of virtual memory can significantly reduce the user experience due to the latency of the storage device (as compared to main memory 404, e.g., DRAM). Further, the use of storage device 421 for virtual memory can significantly reduce the usable life of storage device 421.

[0046] Command 424 may further be transmitted or received via communication network 426 using a transmission medium via a network interface device 420 that utilizes any one of several transfer protocols (e.g., frame relay, Internet Protocol (IP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), etc.). Examples of communication networks can include, among others, local area networks (LANs), wide area networks (WANs), packet data networks (e.g., the Internet), cellular phone networks (e.g., cellular networks), plain old telephone service (POTS), and wireless data networks (e.g., the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard family known as Wi-Fi (registered trademark), the IEEE 802.16 standard family known as WiMax (registered trademark), the IEEE 802.15.4 standard family of peer-to-peer (P2P) networks, etc.). In one example, network interface device 420 may include one or more physical jacks (e.g., Ethernet (registered trademark), coaxial cable, or phone jack) or one or more antennas for connecting to communication network 426. In one example, network interface device 420 may include multiple antennas for performing wireless communication using at least one of single input multiple output (SIMO), multiple input multiple output (MIMO), or multiple input single output (MISO) technologies. The term "transmission medium" is interpreted to include any tangible or intangible medium capable of storing, encoding, or carrying instructions executed by machine 400, including digital or analog communication signals for facilitating such software communication or other tangible or intangible media.

[0047] Each of the non-limiting aspects or examples described herein may stand on its own or may be implemented in various substitutions or combinations with one or more of the other examples. The above detailed description includes references to the accompanying drawings that form a part of the detailed description. The drawings, by way of example, illustrate specific embodiments in which the subject matter of the invention may be practiced. These embodiments are also referred to herein as "examples." Such examples may include other elements in addition to those illustrated or described. However, the inventors contemplate examples in which only the elements illustrated or described are provided. Further, the inventors contemplate examples in which any combination or substitution of these illustrated or described elements (or one or more aspects thereof) is used with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) illustrated or described.

[0048] In the event of any inconsistent usage between this specification and the documents incorporated by reference, the usage in this specification prevails. As used herein, the term "one" is used to mean one or more, independent of the use of other instances or the terms "at least one" or "one or more" as is common in patent documents. As used herein, the term "or" refers to non-exclusive disjunction, unless otherwise specified, such that "A or B" includes "A but not B," "B but not A," and "A and B." As used herein, the term "comprising" is used as a synonym for the term "including." Also, in the following claims, the terms "comprising" and "including" are open-ended, i.e., a system, apparatus, article, composition, process, or method that includes elements recited after such terms in addition to other elements is still considered to be within the scope of that claim. Further, in the following claims, the terms "first," "second," "third," etc. are used merely as labels and are not intended to impose numerical requirements on their objects.

[0049] Examples of the methods described herein can be implemented, at least in part, on a machine or computer. Some examples can include a computer-readable medium or machine-readable medium encoded with transient or non-transient instructions operative to configure an electronic device to perform the methods described in the above examples. Implementations of such methods can include code such as microcode, assembly language code, high-level language code, and the like. Such code can include transient or non-transient computer-readable instructions for performing various methods. The code can form part of a computer program product. Further, in one example, the code can 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 such tangible computer-readable media can 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 sticks, random access memory (RAM), read-only memory (ROM), and the like.

[0050] The above description is for illustrative purposes and not restrictive. For example, the above examples (or one or more aspects thereof) can be used in combination with each other. By considering the above description, other embodiments can be used by those skilled in the art and the like. The abstract is provided to enable the reader to quickly ascertain the nature of the technical disclosure. Thus, it is not used for the purpose of interpreting or limiting the scope or meaning of the claims. Also, in the above detailed description, various features may be grouped together to simplify the disclosure. This should not be construed as intending that any feature of the disclosure not recited in a claim is essential to any claim. Rather, the subject matter of the present invention may be less than all features of a particular disclosed embodiment. Accordingly, the following claims are incorporated into the detailed description as examples or embodiments, each claim standing on its own as a separate embodiment, and such embodiments can be practiced 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 such claims are entitled.

Claims

1. 1. A system comprising: an inductive coupling reader arranged to interrogate a coverage area of ​​the inductive coupling reader for the presence of one or more RF tags in said coverage area, A tuning circuit; A driver circuit; a receiver circuit for receiving, demodulating, and decoding an identification signal from the one or more RF tags within the coverage area; the inductive coupling reader comprising: one or more processors configured to perform the operations; and wherein the operation comprises: applying an excitation frequency to the tuned circuit with the driver circuit; detecting a change in a resonant frequency of the tuned circuit caused by an external interference-inducing material in proximity to the inductively coupled reader; adjusting, with the driver circuit, the excitation frequency applied to the tuning circuit in response to detecting a change in the resonant frequency of the tuning circuit; receiving from the receiver circuit one or more identification signals corresponding to the one or more RF tags within the coverage area; Including, the system.

2. The system of claim 1 , further comprising a non-volatile memory that stores configuration information for the inductive coupling reader.

3. 10. The system of claim 1, further comprising an antenna voltage detection circuit for measuring a value of the voltage dissipated by the tuning circuit.

4. 4. The system of claim 3, wherein the one or more processors are further configured to detect a change in the resonant frequency by receiving the voltage measurement from the antenna voltage detection circuit and compare the voltage measurement to stored thresholds, the stored thresholds including a lower threshold and an upper threshold, and detecting the change in the resonant frequency includes determining whether the voltage measurement is below the lower threshold or above the upper threshold.

5. 2. The system of claim 1, further comprising an adjustable frequency timer, the one or more processors further configured to offset changes in the resonant frequency by adjusting the resonant frequency with the adjustable frequency timer.

6. The one or more processors: applying a first excitation frequency to the tuned circuit using the driver circuit and receiving a first voltage measurement from an antenna voltage detection circuit corresponding to the first excitation frequency; applying a second excitation frequency to the tuned circuit using the driver circuit and receiving a second voltage measurement from the antenna voltage detection circuit corresponding to the second excitation frequency; comparing the first voltage measurement to the second voltage measurement to determine a relative difference in value; determining a third excitation frequency for application to the tuned circuit using the driver circuit based on the relative difference in the values; The system of claim 1 further configured to:

7. 7. The system of claim 6, wherein the one or more processors are further configured to compare the first voltage measurement to a stored threshold and determine a value of the second excitation frequency based on a difference between the first voltage measurement and the stored threshold.

8. 8. The system of claim 7, wherein the one or more processors are further configured to store a higher value of the first voltage measurement and the second voltage measurement as the stored threshold value.

9. The system of claim 6 , wherein the third excitation frequency corresponds to one of the first excitation frequency and the second excitation frequency.

10. The system of claim 6 , wherein the third excitation frequency is higher than both the first excitation frequency and the second excitation frequency.

11. The system of claim 6 , wherein the third excitation frequency is a frequency between the first excitation frequency and the second excitation frequency.

12. The system of claim 1 , wherein the tuning circuit comprises a tuning oscillator circuit configured to generate an initial resonant frequency of 125 kHz or 134 kHz.

13. The system of claim 1 , wherein the inductive coupling reader comprises a radio frequency identification (RFID) reader.

14. The system of claim 1 , wherein detecting a change in the resonant frequency includes accessing configuration information of the inductive coupling reader indicative of the inductive coupling reader being in proximity to an external interference-inducing material.

15. The system of claim 1 , wherein detecting a change in the resonant frequency comprises receiving a voltage measurement from an antenna voltage detection circuit and comparing the voltage measurement to a stored threshold value.

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