Dynamic frequency tuning in inductively coupled systems

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 relates generally, but without limitation, to radio frequency identification (RFID) systems, and specifically to techniques for reducing harmful interference effects in RFID systems. 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 a corresponding item or in the vicinity thereof and contains information identifying that item. When identification is required, a radio frequency reader unit (e.g., an 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 sent back to the reader unit. The reader unit uses the identification information received from the transponder to perform any of a variety of RFID applications. For example, the identification information may be used to perform functions such as asset management, inventory tracking, and access control. SUMMARY OF THE INVENTION

[0003] In some specific embodiments, systems and methods for operating an inductively coupled reader are provided. The systems and methods of the present disclosure perform operations comprising applying an excitation frequency to a resonant circuit of the inductively coupled reader, detecting a change in the resonant frequency of the resonant circuit of the inductively coupled reader, and adjusting the excitation frequency being 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 resonant frequency is brought about by an external metallic material adjacent to the inductively coupled leader, and the range of the inductively coupled leader is reduced in response to the change in the resonant frequency.

[0005] In some embodiments, detecting the change involves accessing configuration information of the inductively coupled reader indicating that the inductively coupled reader is in close proximity to an external metallic material.

[0006] In some embodiments, the resonant circuit includes a tuned vibration circuit configured to produce a constant resonant frequency of 125 kHz or 134 kHz. In some embodiments, the operation includes applying a first excitation frequency to the resonant circuit of the inductively coupled leader, measuring a first amplitude of a first voltage generated across the resonant circuit of the inductively coupled leader 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 the voltage level resulting from the application of a second excitation frequency.

[0008] In some embodiments, the operation includes applying a second excitation frequency to the resonant circuit of the inductively coupled leader, measuring a second amplitude of a second voltage generated across the resonant circuit of the inductively coupled leader 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 inductive coupling device inductively coupled to the inductive coupling reader at the tuned excitation frequency, the inductive coupling device deriving a clock frequency from the tuned excitation frequency so that data transfer between the inductive coupling device and the inductive coupling reader is synchronized to the tuned excitation frequency.

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

[0012] In some embodiments, the adjustment value for 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 inductively coupled reader.

[0013] When a metallic material is in close proximity to a conventional RFID reader, the resonant frequency of the RFID reader's resonant circuit changes due to the metallic material, and therefore the range of the conventional RFID reader is typically reduced by the metallic material. The disclosed embodiment detects interference such as that caused by the metallic material and adjusts the excitation (driving) frequency applied to the resonant circuit in response. This improves the overall power efficiency and range of the disclosed RFID reader compared to 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 description of the subject matter of the invention. A more detailed description is included to provide further information relating to this patent application. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a block diagram showing RFID systems according to various embodiments. [Figure 2A] Figure 2A is a block diagram showing a reader unit used in RFID systems according to various embodiments. [Figure 2B] Figure 2B shows the waveforms of the drive frequency versus resonant frequency of exemplary RFID systems according to various embodiments. [Figure 3] Figure 3 is a flowchart illustrating exemplary processes for operating inductively coupled readers according to various embodiments. [Figure 4] Figure 4 is a block diagram showing an example of a machine capable of carrying out one or more embodiments. [Modes for carrying out the invention]

[0016] The drawings are not necessarily drawn to a fixed scale, and similar reference numerals in the drawings may represent similar components from different viewpoints. Similar reference numerals with different suffixes may represent different examples of similar components. The drawings generally illustrate the various embodiments described herein as examples, not limitations.

[0017] This disclosure describes techniques for operating inductively coupled readers in particular. Specifically, the techniques of this disclosure detect interference and detuning of the resonant circuit of an inductively coupled reader and adjust the excitation (driving) frequency applied to the resonant circuit accordingly. This improves the overall power efficiency and range of inductively coupled readers such as RFID readers, thereby improving the overall efficiency and functionality of the computer.

[0018] In RFID systems, problems arise if one or more external interference signals are present within the system's frequency band during query operations. Such interference can cause misidentification and misreporting of items of interest in an RFID system. Such interference is more likely to occur due to metallic materials located near the system of interest. Such metallic materials significantly reduce the range of the RFID interrogator, particularly by altering the resonant frequency of the RFID interrogator's resonant circuit. For example, if an inductively coupled reader (e.g., a 13.56 MHz RFID reader) is mounted on a metal surface, the apparent inductance of the antenna changes. Since the antenna is part of a parallel resonant circuit used for communication with the RFID transponder (e.g., certificates such as RFID tags), detuning of this circuit reduces actual performance (e.g., reading range), especially because the drive frequency does not match the antenna's resonant frequency. This causes the RFID reader to consume more power to read a given RFID tag, resulting in wasted system resources.

[0019] To address the challenges of such typical situations, the technology of this disclosure detects when the resonant circuit of an inductively coupled reader is detuned and compensates for such detunement by changing the excitation (driving) frequency applied to the resonant circuit. This allows for the recovery and improvement of the performance of the inductively coupled reader, thereby improving the power efficiency and range of the inductively coupled reader. As a result, the overall efficiency and functionality of the computer are improved.

[0020] Figure 1 is a block diagram showing an RFID system according to several embodiments. As shown, the RFID system 8 includes an RF reader unit 12 (inductively coupled reader) and a number of RF identification tags 16, 18, 20, 22, 24, 26, each of which is attached to a corresponding item of interest 34, 36, 38, 40, 42, 44 and used to identify that item. The items of interest 34, 36, 38, 40, 42, 44 may include, for example, a piece of inventory, a person, capital assets, an animal, or any other object that may be desired to be tracked or monitored within a particular area. The number of items that a particular reader can track is usually a matter of design choice.

[0021] The RF reader unit 12 may be 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 the RF reader unit may depend on the reader's transmit power level, the antenna pattern of the reader's transmitting antenna, and the reader's position and orientation at any given time.

[0022] During normal operation of the exemplary system in Figure 1, the RF reader unit 12 periodically interrogates its coverage area 52 to identify items 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 to 26 in the area 52, causing them to transmit 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. Upon receiving the RF interrogation signal, the RF tag derives a local clock frequency based on the RF interrogation signal. The RF tag synchronizes data transmission and reception 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, upon receiving the interrogation signal, responds by returning its identification signal to the interrogating reader. After receiving identification information from all RF tags within the coverage area 52, the RF reader unit reports the collected information to an appropriate entity.

[0023] Referring to FIG. 1, it can be appreciated that interference is likely to occur between the RF reader unit 12 and a metallic material. For example, the RF reader unit 12 may be mounted on a wall including a metallic material. Such a metallic material may 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, which may cause the RF reader unit 12 to misidentify or fail to identify items in a region 52 that is located further 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 may correspond to the resonant frequency expected under conditions where no interference is present. The mismatch between the drive frequency and the resonant frequency increases the overall power consumed by the system and reduces the range of the RF reader unit 12. That is, the size of the region 52 may be reduced when a metallic material is present in the vicinity of the RF reader unit 12. In addition, 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 may increase.

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

[0025] FIG. 2A is a block diagram illustrating an RF reader unit 200 according to an embodiment of the present disclosure. The RF reader unit 200 may be an example of the RF reader unit 12 (FIG. 1). As illustrated, the reader unit 200 may 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 may be omitted 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 RF reader unit 200's coverage area 52. The microcontroller 220 is implemented using a digital processing device such as a general-purpose microprocessor, a digital signal processor, a reduced instruction set computer, a composite instruction set computer, or a field-programmable gate array. In addition, one or more of the other functional blocks shown in Figure 2A may also 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 a query signal (under the control of the microcontroller 220 and driver circuit 230) for transmission into the coverage area 52 via the inductive loop antenna during query operation. The receiver circuit 240, among other things, receives an identification signal from an RF tag located within the coverage area 52, demodulates and decodes the received identification signal, and supplies the resulting identification information to the microcontroller 220.

[0028] In some embodiments, the microcontroller 220 detects a change in the resonant frequency of the RF reader unit 200. Specifically, the microcontroller 220 detects a change in the resonant frequency of the tuning circuit 210. In some implementations, the microcontroller 220 detects the change in resonant frequency based on a preset setting value of the microcontroller 220 stored in the microcontroller 220's non-volatile memory. For example, during operation or manufacturing of the RF reader unit 200, configuration bits stored in the microcontroller 220's non-volatile memory may indicate the presence or absence of interference sources such as metallic materials. The microcontroller 220 can determine whether the configuration bits are asserted or deasserted by accessing them during operation. If the configuration bits are asserted, the microcontroller 220 determines that an interference source such as metallic material is present or very close to the RF reader unit 200. In such cases, the microcontroller 220 detects a change in the resonant frequency of the RF reader unit 200. If the configuration bits are deasserted, the microcontroller 220 determines that no interference source is present.

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

[0030] If the microcontroller 220 determines that the resonant frequency of the tuning circuit 210 has changed, it compensates for the change in resonant frequency by adjusting the excitation frequency of the query signal using an adjustable frequency timer. For example, if the resonant frequency is 10% higher than the expected resonant frequency, the microcontroller 220 increases the excitation frequency by 10%.

[0031] The preset threshold against which the voltage measured by the antenna voltage detection circuit 250 is compared can be set to a value 10% (or any other appropriate percentage or value) higher or 10% (or any other appropriate percentage or value) lower than the voltage consumed by the tuning circuit 210 when no metallic material is in close proximity to the RF reader unit 200. The preset threshold can be programmed into a lookup 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 may be a specific value or a range of values. If the measured voltage is outside the range of values, the microcontroller 220 detects the change in resonant frequency and adjusts the excitation frequency of the query circuit to a specific value.

[0032] In some cases, the microcontroller 220 instructs the driver circuit 230 to operate at a first or second frequency. The first frequency may correspond to the resonant frequency of the tuning circuit 210 under normal conditions where no interference source is present. In response to detecting a change in the resonant frequency (for example, based on a configuration bit value or a 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 query signal based on the voltage value measured by the antenna voltage detection circuit 250. For example, the microcontroller 220 may initially drive the tuning circuit 210 at a first frequency corresponding to the resonant frequency of the tuning circuit 210 under normal conditions where no interference source is present. The microcontroller 220 receives a first voltage measurement from the antenna voltage detection circuit 250. The microcontroller 220 stores this first voltage measurement in its volatile memory. The microcontroller 220 then increases the excitation frequency to drive the tuning circuit 210 at a second frequency higher than the first frequency. The microcontroller 220 receives a second voltage measurement from the antenna voltage detection circuit 250. The microcontroller 220 compares the second voltage measurement with the first voltage measurement. In response to determining that the second voltage measurement is greater than the first voltage measurement, the microcontroller 220 may increase the excitation frequency to drive the tuning circuit 210 at a third frequency higher than the second frequency. Alternatively, in response to determining that the second voltage measurement is greater than the first voltage measurement, 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 is less than the first voltage measurement, the microcontroller 220 may decrease the excitation frequency to drive the tuning circuit 210 at a third frequency lower than the first frequency. Alternatively, in response to determining that the second voltage measurement is less than the first voltage measurement, the microcontroller 220 may set the excitation frequency to drive the tuning circuit 210 at the first frequency.

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

[0035] Figure 2B shows the waveforms of the drive frequency versus resonant frequency of exemplary RFID systems according to various embodiments. As shown in Figure 2B, when the drive frequency of the query signal applied to the resonant circuit does not match the resonant frequency of the resonant circuit, the antenna voltage (and thus the range of the RFID system) decreases. As shown in Figure 2B, the antenna voltage is at its maximum value when the drive frequency matches the resonant or resonance frequency of the resonant circuit. Specifically, under normal operating conditions where there are no interference sources such as metallic materials or where interference sources are not close to the RF reader unit 200, the resonant frequency of the resonant circuit is a preset value of 125 kHz or 134 kHz. The excitation frequency of the query signal applied to the resonant circuit is also 125 kHz or 134 kHz, and the excitation frequency is set to be equal to or match the value of the resonant frequency. The resulting voltage obtained by the antenna voltage detection circuit 250 is close to or at the maximum value. At a later point, if the RF reader unit 200 is placed very close to an interference source such as a metallic material, the resonant frequency of the resonant circuit changes (for example, from 125 kHz to 135 kHz). When the resonant circuit is driven at the currently set excitation frequency (e.g., 125 kHz), the voltage measurement provided by the antenna voltage detection circuit 250 decreases compared to the previously measured maximum voltage value. In response, the excitation frequency is increased or decreased by a specific value that can match the resonant frequency after the resonant circuit has been modified. As a result, when the resonant circuit is driven at the adjusted excitation frequency (e.g., 135 kHz), the voltage measurement 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., an RF tag) receives the RF query signal at a tuned excitation frequency and derives a local clock frequency based on that RF query 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, consequently, the tuned excitation (driving) frequency of the RF query signal.

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

[0038] In operation 320, the inductively coupled reader detects a change in the resonant frequency of the inductively coupled reader's resonant circuit. In operation 330, the inductively coupled leader adjusts the excitation frequency applied to the resonant circuit in response to detecting a change in the resonant frequency of the inductively coupled leader.

[0039] Figure 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 inductively coupled reader. In alternative embodiments, machine 400 may operate as a standalone device or may be connected to other machines (e.g., networked). In a networked deployment, machine 400 may function as a server machine, a client machine, or both in a server-client network environment. 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), tablet PC, set-top box (STB), personal digital assistant (PDA), mobile phone, web appliance, IoT device, automotive system, aerospace system, or any machine capable of executing instructions (sequential or otherwise) that specify the actions performed by such machine. Furthermore, although only a single machine is illustrated, the term “machine” should be interpreted to include any set of machines individually or collectively performing a set (or set) of instructions to perform one or more of the methods described herein, for example, through cloud computing, software as a service (SaaS), or other computer cluster configurations.

[0040] The examples described herein may include, or may operate by, logic, components, devices, packages, or mechanisms. A circuit configuration is a group (e.g., a set) of circuits implemented on a tangible entity that includes hardware (e.g., simple circuits, gates, logic, etc.). Circuit components may be flexible to the passage of time and changes in the underlying hardware. A circuit includes elements that can perform a particular task individually or in cooperation when in operation. In one example, the hardware of a circuit configuration may be designed immutably to perform a particular operation (e.g., one built into the hardware). In one example, the hardware of a circuit configuration may include variablely connected physical components (e.g., execution units, transistors, simple circuits, etc.) that include a computer-readable medium that has been physically modified (e.g., magnetically, electrically, or by the movable arrangement of invariant mass particles) to encode instructions for a particular operation. When connecting physical components, the underlying electrical properties 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 a circuit configuration within the hardware via variable connectors, thereby enabling the execution of a portion of a specific task during operation. Thus, computer-readable media are communicatively coupled to other components of the circuit configuration while the device is operating. In one example, any of the physical components may be used in multiple elements of multiple circuit configurations. For instance, during operation, an execution unit may be used at one point in a first circuit in a first circuit configuration, and at another point in time reused by a second circuit in the first circuit configuration or by a third circuit in a second circuit configuration.

[0041] The machine (e.g., a computer system) 400 may 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), main memory 404, and static memory 406. Some or all of these can communicate with each other via an interlink (e.g., a bus) 408. The machine 400 may 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 may be touchscreen displays. Machine 400 may further include a storage device 422 (e.g., a drive unit), a signal generating 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). Machine 400 may also 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., an infrared (IR)) connection, a near-field communication (NFC) connection, or other) for communicating with or controlling one or more peripheral devices (e.g., a printer, a card reader, etc.).

[0042] The 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 one or more of the technologies or functions described herein. The instructions 424 may reside, all or at least partially, in the main memory 404, in the static memory 406, or in the hardware processor 402 while the instructions 424 are being executed by the machine 400. In one example, the machine-readable medium may consist of one or any combination of the hardware processor 402, the main memory 404, the static memory 406, and the storage device 421.

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

[0044] The term “machine-readable medium” includes temporary or non-temporary media capable of storing, encoding, or carrying temporary or non-temporary instructions for execution by machine 400, which cause machine 400 to execute one or more of the technologies of the present disclosure, or which are capable of storing, encoding, or carrying data structures used by or associated with such instructions. Examples of non-limiting machine-readable media include solid memory, optical media, and magnetic media. In one example, a mass-bearing machine-readable medium includes a machine-readable medium having a plurality of particles having an immutable (e.g., stationary) mass. Thus, a mass-bearing machine-readable medium is not a transient propagating signal. Specific examples of mass-bearing machine-readable media may include non-volatile memory such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable and programmable read-only memory (EEPROM)) and 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 the storage device 421 can be accessed by the main memory 404 for use by the hardware processor 402. Main memory 404 (e.g., DRAM) is a different type of storage than the storage device 421 (e.g., SSD), which is typically fast but volatile and therefore suitable for long-term storage, including periods of being "off". Instructions 424 or data are typically loaded into the main memory 404 for use by the user or machine 400. When the main memory 404 is full, virtual space from the storage device 421 can be allocated to supplement the main memory 404, but since the storage device 421 is typically slower than the main memory 404, with write speeds typically at least twice as slow as read speeds, the use of virtual memory (compared to main memory 404, e.g., DRAM) can significantly reduce the user experience due to the latency of the storage device. Furthermore, the use of storage device 421 for virtual memory can significantly reduce the usable lifespan of storage device 421.

[0046] Instruction 424 may further be transmitted or received over a communication network 426 using a transmission medium via a network interface device 420 that utilizes any one of several transport 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 may include, among others, a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), a mobile phone network (e.g., a cellular network), a plain-old telephone service (POTS), and a wireless data network (e.g., the IEEE 802.11 standard family known as Wi-Fi®, the IEEE 802.16 standard family known as WiMax®, the IEEE 802.15.4 standard family for peer-to-peer (P2P) networks, etc.). In one example, the network interface device 420 may include one or more physical jacks (e.g., Ethernet®, coaxial cable, or telephone jack) or one or more antennas for connecting to the communication network 426. In one example, the network interface device 420 may include multiple antennas for 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 as any tangible or intangible medium capable of storing, encoding, or carrying instructions executed by machine 400, and including digital or analog communication signals or other tangible or intangible mediums for facilitating communication of such software.

[0047] Each of the non-limiting embodiments or examples described herein may constitute itself or may be implemented in various substitutions or combinations with one or more of the other embodiments. The above detailed description includes references to accompanying drawings which constitute part of the detailed description. The drawings illustrate specific embodiments in which the subject matter of the present invention may be carried out. 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 also envision examples in which only the illustrated or described elements are provided. Furthermore, the inventors also envision examples using any combination or substitution of these illustrated or described elements (or one or more embodiments thereof) with respect to a particular example (or one or more embodiments thereof) or to other illustrated or described examples (or one or more embodiments thereof).

[0048] In the event of any inconsistency in usage between this specification and any reference incorporated herein, the usage herein shall prevail. In this specification, the term “one” is used to include one or more, independently of other examples or the use of “at least one” or “one or more,” as is common in the patent literature. In this specification, the term “or” means non-exclusive unless otherwise specified, and “A or B” includes “A but not B,” “B but not A,” and “A and B.” In this specification, the term “includes” is used as synonymous with the term “equipped with.” Furthermore, in the following claims, the terms “includes” and “equipped with” are open, meaning that a system, apparatus, article, composition, method, or process that includes other elements in addition to the elements listed following such terms is still considered to be within the scope of that claim. In addition, 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 their subjects.

[0049] Examples of the methods described herein can be implemented at least partially on a machine or computer. Some examples may include computer-readable or machine-readable media encoded with temporary or non-temporary instructions that are operable to configure an electronic device to perform the methods described in the examples above. Implementations of such methods may include code such as microcode, assembly language code, or high-level language code. Such code may include temporary or non-temporary computer-readable instructions for performing various methods. The code may form part of a computer program product. Furthermore, in one example, the code may be tangibly stored in one or more volatile, non-temporary, or non-volatile tangible computer-readable media during execution or at other times. Examples of these tangible computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact discs and digital video discs), magnetic cassettes, memory cards or sticks, random access memory (RAM), read-only memory (ROM), and the like.

[0050] The above description is illustrative and not limiting. For example, the above examples (or one or more embodiments thereof) may be used in combination with each other. Other embodiments may be used by those skilled in the art by considering the above description. The abstract is provided so that readers can quickly confirm the nature of the technical disclosure. It is not intended to 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 to simplify the disclosure. This should not be interpreted as meaning that any disclosed feature not described in the claims is essential to any claim. Rather, the subject matter of the invention may be fewer features than all the features of a particular disclosed embodiment. Accordingly, the following claims are incorporated into the detailed description as examples or embodiments, and each claim stands independently as a separate embodiment, and such embodiments may be implemented with respect to each other in various combinations or substitutions. The scope of the subject matter of the invention should be determined by referring to the appended claims, along with the entire scope of equivalents to which such claims are effective.

Claims

1. It is a system, An inductively coupled reader configured to query the coverage area of ​​the inductively coupled reader to determine whether one or more RF tags are present in the coverage area of ​​the inductively coupled reader, A tuning circuit and Driver circuit and A receiving circuit for receiving, demodulating, and decoding identification signals from one or more RF tags within the coverage area. The inductively coupled reader includes, One or more processors configured to perform an operation, The above operation is provided, Applying the excitation frequency to the tuning circuit using the driver circuit, To detect a change in the resonant frequency of the tuning circuit, the change in the resonant frequency caused by an external interference-inducing material located in close proximity to the inductively coupled leader, In response to detecting a change in the resonant frequency of the tuning circuit, the excitation frequency applied to the tuning circuit is adjusted using the driver circuit. The receiving circuit receives one or more identification signals corresponding to one or more RF tags within the coverage area. A system that includes this.

2. The system according to claim 1, further comprising a non-volatile memory for storing configuration information of the inductively coupled reader.

3. The system according to claim 1, further comprising an antenna voltage detection circuit for measuring the value of the voltage consumed by the tuning circuit.

4. The system according to claim 3, wherein one or more processors are further configured to detect a change in the resonant frequency by receiving a measured value of the voltage from the antenna voltage detection circuit, and to compare the measured value of the voltage with 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 measured value of the voltage is below the lower threshold or above the upper threshold.

5. The system according to claim 1, further comprising an adjustable frequency timer, wherein one or more processors are further configured to cancel out changes in the resonant frequency by adjusting the excitation frequency using the adjustable frequency timer.

6. The one or more processors described above are The driver circuit is used to apply the first excitation frequency to the tuning circuit, and a first voltage measurement value corresponding to the first excitation frequency is received from the antenna voltage detection circuit. Using the driver circuit, a second excitation frequency higher than the first excitation frequency is applied to the tuning circuit, and a second voltage measurement corresponding to the second excitation frequency is received from the antenna voltage detection circuit. The first voltage measurement and the second voltage measurement are compared, Based on whether the second voltage measurement is greater than or less than the first voltage measurement, the driver circuit is used to determine a third excitation frequency to be applied to the tuning circuit. It is further structured in the following way: Determining the third excitation frequency is If the second voltage measurement is greater than the first voltage measurement, set the excitation frequency to a higher frequency than the second excitation frequency or set the second excitation frequency to the third excitation frequency, and If the second voltage measurement is smaller than the first voltage measurement, set the excitation frequency to a frequency lower than the first excitation frequency, or set the first excitation frequency to the third excitation frequency. The system according to claim 1, including the following:

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

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

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

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

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

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

13. The system according to claim 1, wherein the inductively coupled reader includes a radio frequency identification (RFID) reader.

14. The system according to claim 1, wherein detecting the change in the resonant frequency includes accessing configuration information of the inductively coupled leader indicating that the inductively coupled leader is in close proximity to an external interference-inducing material.

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

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