System and method for differentiating active and passive NFC devices based on carrier frequency adjustment

Abstract

A near field communication (NFC) reader detects whether an NFC device is a passive NFC device or an active NFC device. The NFC reader outputs an interrogation signal and a carrier signal. When the NFC reader receives a response signal from the NFC device in response to the interrogation signal, the NFC reader adjusts the frequency of the carrier signal before the end of the response signal. The NFC reader determines whether the NFC device is a passive NFC device or an active NFC device based on the characteristics of the remaining portion of the response signal.

Description

Technical Field

[0001] The present disclosure relates to the field of Near Field Communication (NFC). More specifically, the present disclosure relates to identifying NFC devices via an NFC reader. Background Art

[0002] NFC technology utilizes radio frequency signals to enable devices to communicate with each other within a short distance. Many applications of NFC technology utilize an NFC reader to interrogate and receive data from an NFC device. The NFC reader typically outputs an interrogation signal. If the NFC device is within the range of the interrogation signal, the NFC device responds by providing an identification signal that identifies the NFC device. After the NFC device has identified itself, the NFC reader and the NFC device can further exchange information.

[0003] NFC devices can be classified as passive NFC devices or active NFC devices. Generally, passive NFC devices are powered by energy collected from the carrier signal of the NFC reader. Active NFC devices differ from passive NFC devices in that they include their own power source. In addition, there are different types of active NFC devices. Summary of the Invention

[0004] Embodiments of the present disclosure provide an NFC reader capable of distinguishing between passive NFC devices and active NFC devices. The NFC reader transmits a carrier signal at a standard NFC frequency. When the NFC reader receives the start of a response from the NFC device, the NFC reader adjusts the frequency of the carrier signal to a non-standard frequency. The NFC reader then receives the remainder of the response while transmitting the carrier signal at the non-standard frequency. The NFC reader can distinguish between passive NFC devices and active NFC devices based on the characteristics of the remainder of the response signal.

[0005] In one embodiment, an NFC reader can further distinguish between different types of active NFC devices. The NFC reader can adjust the frequency of the carrier signal to a first non-standard frequency while receiving an initial portion of the response from the NFC device to determine whether the NFC device is an active NFC device or a passive NFC device. If the NFC device is an active NFC device, the NFC reader initiates communication at the standard frequency again and then switches the carrier signal to a second non-standard frequency after receiving the start of the response. The NFC reader determines what type of active NFC device is present based on the remainder of the response while transmitting the carrier signal at the second non-standard frequency.

[0006] In one embodiment, the NFC reader initiates communication with the NFC device while transmitting a carrier signal at a non - standard frequency. The NFC reader analyzes the frequency of the response signal to determine whether the NFC device is a passive NFC device or an active NFC device of the first type or the second type.

[0007] In one embodiment, the NFC reader initiates communication with the NFC device while transmitting a carrier signal at a standard frequency. After receiving the initial part of the response, the NFC reader switches the carrier frequency to a non - standard frequency. The NFC reader determines whether the NFC device is a passive NFC device or an active NFC device of the first type or the second type based on the frequency of the response signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a block diagram of an NFC system according to one embodiment.

[0009] Figure 2 is a block diagram of an NFC system according to one embodiment.

[0010] Figures 3A - 3C is a timing diagram of an NFC signal according to one embodiment.

[0011] Figure 4 is a flowchart of a process for operating an NFC system according to one embodiment.

[0012] Figure 5 is a flowchart of a process for operating an NFC system according to one embodiment.

[0013] Figure 6 is a flowchart of a process for operating an NFC system according to one embodiment.

[0014] Figure 7 is a flowchart of a process for operating an NFC system according to one embodiment.

[0015] Figure 8 is a flowchart of a process for operating an NFC system according to one embodiment.

[0016] Figure 9 is a schematic diagram of an NFC reader according to one embodiment.

[0017] Figure 10 is a schematic diagram of an NFC system according to one embodiment. DETAILED DESCRIPTION

[0018] Figure 1FIG. 0 is a block diagram of a near field communication (NFC) system 100 according to one embodiment. The NFC system 100 includes an NFC reader 102 and an NFC device 104. The NFC reader 102 and the NFC device 104 communicate with each other using NFC technology.

[0019] The NFC reader 102 outputs a carrier signal. The carrier signal is a radio frequency signal that facilitates NFC communication... The NFC reader 102 outputs an interrogation signal by modulating the carrier signal. The interrogation signal is configured to induce a response from an NFC device within the communication range of the NFC reader 102. If the NFC device 104 is within the range of the NFC reader 102, the NFC device 104 can respond to the interrogation signal.

[0020] In one embodiment, the NFC reader 102 outputs an interrogation signal according to one or more NFC protocols. The NFC protocol defines the structure of the interrogation signal. The protocol can define the frequency of the interrogation signal, the type of data included in the interrogation signal, the amount of data included in the interrogation signal, and the duration of the interrogation signal. Some common NFC protocols define a standard frequency of 13.56 MHz for the carrier signal, although other standard frequencies are possible according to the NFC protocol or future updated versions of the NFC protocol.

[0021] If the NFC device 104 operates using the same protocol as the interrogation signal, the NFC device 104 will respond to the interrogation signal. The protocol also defines the structure of the initial response of the NFC device 104 to the interrogation signal from the NFC reader 102.

[0022] In one embodiment, the NFC device 104 is a passive load modulation NFC device 104. A passive load modulation NFC device does not have its own power source. Instead, a passive load modulation NFC device is powered by the carrier signal output from the NFC reader 102. Accordingly, the passive load modulation NFC device includes an energy harvesting circuit that harvests energy from the carrier signal output from the NFC reader 102. As used herein, the term "passive NFC device" may be used interchangeably with the term "passive load modulation NFC device".

[0023] Passive load modulation involves modifying the impedance of the antenna coil of a passive NFC device at the rate of a load modulation signal carrying data. This impedance modulation is echoed through inductive coupling in the impedance of the antenna coil of the NFC reader 102. The NFC reader 102 can extract the load modulation signal used by the passive NFC device from its antenna signal. In this way, the NFC reader 102 can extract identification or other data from the passive NFC device. The passive load modulation NFC devices described herein can operate according to well-known passive load modulation techniques. Since the passive NFC device is powered by energy collected from the carrier signal, the passive NFC device modulates its impedance according to the frequency of the carrier signal.

[0024] In one embodiment, the NFC device 104 is an active load modulation NFC device. The active load modulation NFC device is powered by a power source separate from the NFC reader 102. Thus, when the active load modulation NFC device receives an interrogation signal, the active load modulation NFC device responds by outputting a radio frequency signal and modulating the radio frequency signal at the power of a power source separate from the NFC reader 102. Data is transmitted from the NFC device 104 by modulating the radio frequency signal output by the NFC device 104. As used herein, the term "active NFC device" may be used interchangeably with the term "active load modulation NFC device". Without departing from the scope of the present disclosure, active load modulation may be implemented in other ways.

[0025] Active and passive load modulation NFC devices typically operate according to a specific protocol. In particular, passive load modulation NFC devices typically operate according to a different subset of NFC protocols than active load modulation NFC devices. In most cases, the NFC reader 102 can accurately determine whether the NFC device 104 is an active NFC device or a passive NFC device based on the protocol employed by the NFC device 104 in response to the NFC reader 102.

[0026] Some NFC protocols specify that the phase of the response signal output by an active NFC device should be within a selected phase difference from the carrier signal. For example, an NFC protocol may specify that the phase difference between the carrier signal and the response signal should be less than 30°. Thus, an active NFC device typically attempts to lock the phase of the response signal to the phase of the carrier signal. If the carrier signal is 13.56 MHz, the active NFC device typically transmits the response signal at 13.56 MHz. The active NFC device also locks the phase of the response signal to the phase of the carrier signal.

[0027] Generally, there are two ways for an active NFC device to synchronize the phase of the response signal with the phase of the carrier signal. The first type of phase synchronization is in-frame synchronization (IFS). The second type of phase synchronization is out-of-frame synchronization (OOFS). The NFC communication frame starts with the transmission of an interrogation signal from the NFC reader 102. This frame continues with the reception of a response signal from the NFC device 104. Thus, the NFC communication frame extends from the start of the interrogation signal to the end of the response signal. As used herein, an active NFC device based on IFS can be referred to as an IFS active NFC device or a type 1 active NFC device. As used herein, an active NFC device based on OOFS can be referred to as an OOFS active NFC device or a type 2 active NFC device.

[0028] There are situations in which the NFC device 104 can operate according to a protocol that does not correspond to its true nature. In some cases, the NFC device 104 can be a passive NFC device that operates according to a protocol typically reserved for active NFC devices. In other cases, the NFC device 104 can be an active NFC device that operates according to a protocol typically reserved for passive NFC devices. If the NFC reader cannot correctly identify the type of the NFC device, the NFC device may be damaged.

[0029] For example, many mobile phones act as NFC devices. Mobile phones are active NFC devices. In many cases, users physically attach a credit card or an ID card to their mobile phones. These credit cards and ID cards are typically passive NFC devices. The mobile phone can also include a software application that enables the credit card to be "cloned" onto the mobile phone. Cloning a credit card corresponds to using the NFC application to store information related to the credit card, such as the credit card number, expiration date, and billing ZIP Code. When the mobile phone is placed within the range of the NFC reader, the mobile phone communicates with the NFC reader as if the mobile phone were a credit card. Based on such interactions, a traditional NFC reader may assume that only a passive NFC device (credit card) is present. In other cases, because the credit card or ID card is physically coupled to the mobile phone, the traditional NFC reader can communicate with the mobile phone and may not identify the additional presence of one or more passive NFC devices.

[0030] In one embodiment, the NFC reader 102 or an electronic device incorporating the NFC reader 102 includes a wireless charging circuit device separate from the NFC communication circuitry. If the NFC device 104 is an active NFC device, the wireless charging circuit device has the ability to charge the battery of the NFC device 104. In particular, the wireless charging circuit device is capable of outputting a charging field. The active NFC device can collect energy from the charging field. In this way, the wireless charging circuit device can charge the battery of the active NFC device.

[0031] When describing an embodiment in which a separate wireless charging circuit device is used to charge the battery of an active NFC device, the NFC reader 102 can be described as including the wireless charging circuit device. The wireless charging circuit device includes an antenna coil that is separate from the NFC communication antenna of the NFC reader 102 and does not operate according to the NFC communication frequency and protocol. Thus, the NFC reader 102 can be a device that includes both NFC communication circuitry and a separate wireless charging circuit device.

[0032] In one embodiment, the wireless charging circuit device operates according to the Qi wireless charging standard. The Qi wireless charging circuit device outputs a charging field in the range between 87 KHz and 205 KHz. NFC signals typically communicate at a frequency of 13.56 MHz. Thus, the Qi charging field is outside the frequency range of the NFC communication signal.

[0033] A passive NFC device may be damaged by the charging field output by the wireless charging circuit device. If the NFC reader misidentifies a passive NFC device as an active NFC device, the NFC reader may cause the wireless charging circuit device to output a charging field that may damage the passive NFC device.

[0034] The NFC reader 102 is capable of reliably identifying whether the NFC device 104 is an active NFC device or a passive NFC device. The NFC reader 102 is also capable of identifying whether the active NFC device is an IFS active NFC device or an OOFS active NFC device. As described above, in some cases, a passive NFC device may utilize a protocol typically associated with an active NFC device, or vice versa. Thus, after the NFC reader 102 has initially established communication with the NFC device 104, the NFC reader 102 performs further tests to determine whether the NFC device 104 is an active NFC device or a passive NFC device. Thus, the NFC reader 102 does not determine whether the NFC device 104 is an active device or a passive device based solely on the NFC protocol employed by the NFC device 104 during operation.

[0035] When the NFC reader 102 outputs an interrogation signal, the NFC reader 102 also outputs a carrier signal. The NFC device 104 responds by providing an identification signal or another type of response signal. The identification signal is defined by a frame during which the NFC device 104 transmits a radio frequency signal and modulates the radio frequency signal. The modulation of the radio frequency signal corresponds to the data provided by the NFC device 104. The start of the modulated radio frequency signal from the NFC device 104 corresponds to the start of the frame. The end of the modulated frequency signal from the NFC device 104 corresponds to the end of the frame. As elaborated in more detail below, the NFC reader 102 utilizes the structure of the response to reliably determine whether the NFC device 104 is a passive NFC device or an active NFC device. The NFC reader can also determine whether the active NFC device 104 is an IFS active NFC device or an OOFS active NFC device.

[0036] In one embodiment, the NFC reader 102 transmits a carrier signal at a first, standard frequency. The NFC reader transmits an interrogation signal by modulating the carrier signal. After transmitting the interrogation signal, the NFC reader 102 continues to transmit the carrier signal. When the NFC reader 102 receives the start of a frame of a response or identification signal from the NFC device 104, the NFC reader 102 adjusts the frequency of the carrier signal to a non-standard frequency. This adjustment of the frequency of the carrier signal during the frame can be used to determine whether the NFC device 104 is an active NFC device or a passive NFC device.

[0037] The NFC reader 102 listens for the remainder of the response while outputting the carrier signal at the non-standard frequency. In one embodiment, the value of the non-standard frequency is selected such that a passive NFC device can complete the response signal without error, while an active NFC device will not be able to provide the remainder of the response signal without error. If there is an error in the remainder of the response, the NFC reader 102 determines that the NFC device 104 is an active NFC device. If there is no error in the remainder of the response, the NFC reader 102 determines that the NFC device 104 is a passive NFC device.

[0038] In one embodiment, the value of the non-standard frequency is selected such that an IFS active NFC device can transmit the remainder of the response without error, while an OOFS active NFC device cannot transmit the remainder of the response without error. Due to the different phase synchronization processes used by IFS and OOFS active NFC devices, an IFS active NFC device can transmit an error-free response for a wider range of non-standard carrier frequencies compared to an OOFS active NFC device. The reason for this Figures 2 - 3CIt will be described in more detail. Thus, if the frequency of the carrier signal is incrementally adjusted from the standard carrier signal, the OOFS active NFC device will lose the ability to provide an error-free response signal before the IFS active NFC device loses the ability to provide an error-free response signal. Thus, when it is determined that the NFC device 104 is an IFS active NFC device or an OOFS active NFC device, the NFC reader selects a non-standard carrier signal frequency that is deviated from the standard frequency further than what the OOFS can handle, but not so far that the IFS active NFC device cannot reliably process the response.

[0039] The NFC reader 102 can use various processes to determine whether the NFC device is a passive NFC device, an IFS active NFC device, or an OOFS active NFC device. In one example, at the start of the first frame, the NFC reader 102 transmits a carrier signal at the standard frequency. After receiving the start of the response from the NFC device 104, the NFC reader 102 adjusts the frequency of the carrier signal to a first non-standard frequency at which the passive NFC device can still respond reliably, but the active NFC devices in both devices cannot respond reliably. If the remainder of the response is error-free or otherwise has standard characteristics, the NFC device 104 is a passive NFC device. If the remainder of the response includes errors or otherwise cannot be completed, the NFC device 104 is an active device. If the NFC device 104 is an active NFC device, the NFC reader 102 initiates a second frame by transmitting a carrier signal at the standard frequency. After receiving the start of the response from the NFC device 104, the NFC reader 102 adjusts the frequency of the carrier signal to a second non-standard frequency at which the IFS active NFC device can respond reliably, but the OOFS active NFC device cannot respond reliably. If the remainder of the response in the second frame is error-free, the NFC device 104 is an IFS active NFC device. If the remainder of the response in the second frame has errors, the NFC device 104 is an OOFS active NFC device. In this example, the first frequency is further from the standard frequency than the second frequency. In an alternative example, the NFC reader 102 can switch to a non-standard frequency in the first frame, which is selected to distinguish an OOFS active NFC device from an IFS or passive device. The NFC reader can then switch to a non-standard frequency in the second frame, which is selected to distinguish an IFS active NFC device from a passive device. Thus, by analyzing the responses at two different non-standard frequencies in separate frames in any order, the NFC reader 102 can determine whether the NFC device 104 is a passive NFC device, an IFS active NFC device, or an OOFS active NFC device.

[0040] The NFC reader 102 can distinguish an OOFS active NFC device or an IFS active NFC device or a passive NFC device by analyzing the frequency characteristics of the response signal. In one embodiment, the NFC reader 102 initially transmits a carrier signal at a standard frequency, as described above. After receiving the initial portion of the response, the NFC reader 102 adjusts the frequency of the carrier signal to a non-standard frequency. The NFC reader 102 listens for the remaining portion of the response and analyzes the frequency characteristics of the remaining portion of the response. The main frequency of the remaining portion of the response signal of the OOFS active NFC device will be at the standard frequency. The IFS active NFC device or the passive NFC device will have a frequency response aligned with the non-standard frequency.

[0041] In one embodiment, the NFC reader 102 initially transmits a carrier signal at a non-standard frequency. The NFC reader 102 analyzes the frequency characteristics of the response. The main frequency of the response signal of the OOFS active NFC device will be at the standard frequency. The IFS active NFC device or the passive NFC device will have a frequency response aligned with the non-standard frequency.

[0042] The NFC reader 102 is capable of selectively causing the wireless charging circuit device to output a charging signal based on whether the NFC device 104 is an active NFC device or a passive NFC device. If the NFC reader 102 determines that the NFC device 104 is an active NFC device, the NFC reader 102 can cause the wireless charging circuit device to output a charging field to charge the battery of the NFC device 104. If the NFC reader 102 determines that the NFC device 104 is a passive NFC device, the NFC reader 102 does not cause the wireless charging circuit device to output a charging field. In this way, the NFC reader 102 will prevent the wireless charging circuit device from damaging the passive NFC device by outputting a charging field that the passive NFC device cannot safely withstand.

[0043] Figure 2 is a block diagram of an NFC communication system 200 according to one embodiment. The NFC communication system 100 includes an NFC reader 102, a passive NFC device 104A, an OOFS active NFC device 104B, and an IFS active NFC device 104C. The NFC reader 102 communicates with the passive NFC device 104A, the IFS active NFC device 104B, and the OOFS active NFC device 104C via the NFC communication protocol.

[0044] The NFC reader 102 includes an RF transceiver 111, a reader control system 113, a power supply 108, a charging bay 110, and a wireless charging circuit device 112. The reader control system 113 includes control logic 115. The components of the NFC reader 102 cooperate together to provide NFC communication and separate wireless charging.

[0045] The RF transceiver 111 enables the NFC reader 102 to transmit and receive signals. The RF transceiver 111 may include one or more antennas for transmitting NFC signals and for receiving NFC signals. The RF transceiver 111 may include additional circuitry for enabling the RF transceiver 111 to transmit signals (including interrogation signals, carrier signals, and other types of signals). The RF transceiver 111 may include additional circuitry for enabling the RF transceiver 111 to receive and process signals (including interrogation signals and other types of signals) from the passive NFC device 104A, the IFS active NFC device 104B, and the OOFS active NFC device 104C.

[0046] The reader control system 113 includes control circuitry for controlling the functions of the NFC reader 102. The reader control system 113 controls the operation of the RF transceiver 111. The reader control system 113 controls the transmission of signals with the RF transceiver 111. The reader control system 113 also controls the reception of signals with the RF transceiver 111. The reader control system 113 may include processing resources, memory resources, and data transmission resources.

[0047] The control system 113 includes control logic 115. The control logic 115 may include instructions for controlling the operation of the system 113. The control logic 115 may include an instruction protocol for performing the operations, processes, and methods (including the operations, processes, and methods described herein) performed by the NFC reader 102. The control logic 115 may correspond to software instructions stored in the memory of the NFC reader 102.

[0048] The power supply 108 supplies power to the NFC reader 102. The power supply 108 may include one or more of an internal battery, a wired power connection to an external power supply, and a wireless power connection to an external power supply.

[0049] The wireless charging circuitry 112 selectively provides a wireless charging field based on the type of NFC device determined by the NFC reader 102. The wireless charging circuitry 112 includes an antenna that is separate from the NFC communication antenna of the NFC reader 102 and does not operate according to the NFC communication frequency and protocol. Thus, the NFC reader 102 may be a device that includes both NFC communication circuitry and a separate wireless charging circuitry.

[0050] In one embodiment, the wireless charging circuit device 112 operates according to the Qi wireless charging standard. The Qi wireless charging circuit device outputs a charging field in the range between 87 KHz and 205 KHz. NFC signals typically communicate at a frequency of 13.56 MHz. Thus, the Qi charging field is outside the range of the NFC communication signal. Without departing from the scope of the present disclosure, the wireless charging circuit device 112 may also operate according to other charging protocols or standards other than Qi.

[0051] The wireless charging circuit device 112 of the NFC reader 102 may be controlled by its own control logic, by the control logic 115 of the reader control system 113, or by other control systems. The wireless charging circuit device selectively outputs a wireless charging field based on the type of NFC device present detected by the reader control system 113.

[0052] The charging stand 110 includes a physical area on which the OOFS active NFC device 104C may be positioned to receive a wireless charging signal from the NFC reader 102. When the OOFS active NFC device 104C is positioned on the charging stand 110, the NFC reader 102 detects that the NFC device 104A is an active NFC device and causes the charging field circuit device 112 to begin outputting a wireless charging field.

[0053] In one embodiment, positioning either or both of the passive NFC device 104A and the passive NFC device 104A on the charging stand 110 enables the NFC reader 102 to establish communication with the NFC devices described herein and determine the type of NFC device. The wireless charging circuit device 112 may then output a full charging field, output a reduced charging field, or inhibit the output of the charging field.

[0054] The passive NFC device 104A includes an antenna coil 120, control logic 122, an energy harvesting circuit device 124, and a memory 126. The antenna coil includes one antenna and other circuitry for receiving signals from the NFC reader 102 and for providing signals to the NFC reader 102.

[0055] The control logic 122 controls the operation of the antenna coil 120. The control logic 122 controls the modulation of the signal output from the antenna coil 120 in response to an interrogation signal received from the NFC reader 102. The control logic 122 controls the modulation of the impedance of the antenna coil 120. The memory 126 stores identification data associated with the passive NFC device 104A.

[0056] When antenna coil 120 receives a signal from NFC reader 102, energy harvesting circuitry 124 harvests energy from the signal. Energy harvesting circuitry 124 uses the energy harvested from the signal to power the control logic. When antenna coil 120 receives an interrogation signal from NFC reader 102, the control logic retrieves identification data from memory 126 and causes antenna coil 120 to provide an identification signal including the identification data by impedance matching the impedance of antenna coil 120 according to well-known techniques.

[0057] Since antenna coil 120 is driven by a carrier signal from NFC reader 102, passive NFC device 104A can transmit a response signal at a frequency significantly different from the standard frequency, and this response signal can be received error-free by NFC reader 102. As will be elaborated in more detail below, this enables passive NFC device 104A to transmit a response signal that can be received error-free by NFC reader 102, or to transmit a larger frequency difference than IFS active NFC device 104B and OOFS active NFC device 104C can transmit.

[0058] IFS active NFC device 104B includes RF transceiver 130b, controller 132b, memory 138b, and battery 136b. RF transceiver 130b includes one or more antennas and other RF circuitry for receiving signals from NFC reader 102 and outputting signals to NFC reader 102.

[0059] Controller 132b controls the operation of RF transceiver 130b. Controller 132b may include processing resources for signal processing, for controlling RF transceiver 130b, for reading data from memory 138b, and for writing data to memory 138b.

[0060] Memory 138b may store software instructions for the operation of active NFC device 104. Memory 138b may store data, including identification and other parameters associated with IFS active NFC device 104B.

[0061] Battery 136b provides power to the components of IFS active NFC device 104B. Since IFS active NFC device 104B includes battery 136b, IFS active NFC device 104B does not need to harvest energy from the carrier signal transmitted by NFC reader 102 in order to transmit a signal to NFC reader 102.

[0062] The IFS active NFC device 104B further includes a phase-locked loop (PLL) 134b. The PLL 134b participates in the phase synchronization of the IFS active NFC device 104B. As described above, the IFS active NFC device 104B synchronizes the phase of the response signal with the phase of the carrier signal of the NFC reader 102 within and / or outside the frame. The IFS active NFC device 104B can synchronize or lock the phase at the start of the frame (when the NFC reader 102 first transmits an interrogation signal). The RF transceiver 130b receives the interrogation signal, the carrier signal, and the PLL 134b synchronizes the phase of the response signal with the phase of the carrier signal. The IFS active NFC device does not have an internal clock. The carrier signal is the source of the clock signal for the IFS active NFC device 104B. As will be elaborated in more detail below, the lack of an onboard clock in the IFS active NFC device 104B results in the response signal that the IFS active NFC device 104B can transmit being received error-free at a greater frequency difference from the standard frequency compared to the response signal that the OOFS active NFC device 104C can transmit. However, the presence of the PLL 134b, which is designed to expect the standard frequency, cannot transmit a response signal that can be received error-free at a frequency as high as the frequency difference from the standard frequency like the passive NFC device 104A.

[0063] The OOFS active NFC device 104C includes an RF transceiver 130c, a controller 132c, a memory 138c, and a battery 136c. The RF transceiver 130c includes one or more antennas and other RF circuitry for receiving signals from the NFC reader 102 and outputting signals to the NFC reader 102.

[0064] The controller 132c controls the operation of the RF transceiver 130c. The controller 132c may include processing resources for signal processing, for controlling the RF transceiver 130c, and for reading data from and writing data to the memory 138c.

[0065] The memory 138c may store software instructions for the operation of the active NFC device 104. The memory 138c may store data, including the identification and other parameters associated with the OOFS active NFC device 104C.

[0066] The battery 136c provides power to the components of the OOFS active NFC device 104C. Since the OOFS active NFC device 104C includes the battery 136c, the active NFC device 1028 does not need to collect energy from the carrier signal transmitted by the NFC reader 102 in order to transmit a signal to the NFC reader 102.

[0067] The OOFS active NFC device 104C also includes a PLL 134c and a clock 140. The PLL 134c and the clock 140 are involved in the phase synchronization of the OOFS active NFC device 104C with the NFC reader 102. The OOFS active NFC device 104C generates a clock signal using the clock 140. The clock 140 generates a clock signal having a standard NFC clock frequency. In one example, the standard NFC clock frequency is 13.56 MHz. The clock 140 generates a clock signal having this frequency because the standard frequency is the expected frequency of the carrier signal. The OOFS active NFC device 104C utilizes the PLL 134c to synchronize the phase of the clock signal used by the RF transceiver 130c with the phase of the carrier signal provided by the RF transceiver 111 of the NFC reader 102.

[0068] As previously described, the OOFS active NFC device 104C synchronizes the phase of the response signal with the phase of the carrier signal of the NFC reader 102 outside of the frame. The OOFS active NFC device 104C can synchronize or lock the phase before the first frame and between frames. This is possible because the NFC reader 102 transmits an unmodulated carrier signal for a short period of time before initiating a frame by relaying an interrogation signal. During this short period of time before the start of receiving the interrogation signal, the OOFS active NFC device 104C synchronizes the phase of the clock signal provided by the clock 140 with the phase of the carrier signal received from the NFC reader 102.

[0069] Because the OOFS active NFC device utilizes the built-in clock 140, when the NFC reader 102 has switched the frequency of the carrier signal to a non-standard frequency, the OOFS active NFC device 104C is less able to transmit a response that can be received by the NFC reader 102. Generally, the clock 140 will only generate a clock signal having the standard NFC frequency. Thus, when the carrier signal from the NFC reader 102 has a non-standard frequency, the OOFS active NFC device 104B will still transmit a response according to the standard frequency. As a result, the NFC reader 102 will receive an out-of-phase and unreadable response from the OOFS active NFC device 104C. The NFC reader 102 will determine that the response signal is in error. Therefore, the use of the built-in clock 140 by the OOFS active NFC device 104C is one reason that the response signal from the OOFS active NFC device 104C will be detected as being in error at a lower frequency difference than the IFS active NFC device 104B.

[0070] Figure 3A A timing diagram of the signals transmitted and received by the NFC reader 102 according to one embodiment is shown. In Figure 3AIn the example, the carrier signal is broadcast at the standard frequency of the entire frame. The y-axis corresponds to the signal strength at the RF transceiver 111 of the NFC reader 102. The x-axis corresponds to time.

[0071] Graph 302 corresponds to the communication with the OOFS active NFC device. At time t0, the NFC reader broadcasts a carrier signal at the standard frequency. Between time t0 and t1, the OOFS active NFC device establishes phase synchronization with the carrier signal of the NFC reader 102. At time t1, the NFC reader 102 transmits an interrogation signal by modulating the carrier signal. Time t1 corresponds to the start of the frame. At time t2, the NFC reader 102 stops transmitting the interrogation signal and continues to transmit the unmodulated carrier signal until time t3. At time t3, the NFC reader 102 receives the start of the response signal from the OOFS active NFC device. The response signal received by the NFC reader 102 from the OOFS active NFC device is represented by a higher peak intensity and signal modulation. The NFC reader 102 receives the response signal until time t5. Time t5 corresponds to the end of the frame. The frame corresponds to the time between t1 and t5. In Figure 3A the example, the frequency of the carrier signal has not been adjusted. Therefore, the response signal is received from the OOFS active NFC device without error. The significance of time t4 will be described with respect to Figure 3B and Figure 3C to describe.

[0072] Graph 304 corresponds to the communication with the IFS active NFC device 104B. Graph 304 is basically the same as Graph 302 because when the carrier signal remains at the standard frequency throughout the frame, the response signals from both the IFS active NFC device 104B and the OOFS active NFC device 104C are received by the NFC reader 102 without error. Although not obvious in Figure 3A the IFS active NFC device 104B performs phase synchronization during the frame. In one example, the IFS active NFC device 104B performs phase synchronization while transmitting the response signal between time t3 and t5.

[0073] Graph 306 corresponds to the communication with the passive NFC device 104A. Graph 306 is basically similar to Graphs 302 and 304, except that the response signal from the passive NFC device 104A is indicated by a modulation that reduces the signal strength at the RF transceiver 111 of the NFC reader 102.

[0074] In one embodiment, the duration of the interrogation signal is between 60 μs and 80 μs. In one embodiment, the delay between the transmission of the interrogation signal and the reception of the start of the identification signal is between 70 μs and 100 μs. In one embodiment, the expected duration of the identification signal is between 140 μs and 200 μs. In one embodiment, the delay between the reception of the start of the frame and the adjustment of the frequency of the carrier signal is between 10 μs and 100 μs. Those skilled in the art will recognize that, in accordance with the present disclosure, other values for the timing of the various signals can be used without departing from the scope of the present disclosure.

[0075] Figure 3B represents the situation where the NFC reader 102 adjusts the frequency of the carrier signal after receiving the start of the response signal. In Figure 3B NFC reader 102 adjusts the frequency of the carrier signal from the standard frequency to a non-standard frequency at which the response signal from the OOFS active NFC device 104C cannot be reliably received, but the response signals from the IFS active NFC device 104B and the passive NFC device 104A can be reliably received without error.

[0076] Between times t0 and t4, the operation of the NFC reader 102 is the same as the operation described with respect to Figure 3A Reference Figure 3B to the graph 302, graph 302 corresponding to communication with the OOFS active NFC device 104C, after the NFC reader 102 receives the initial portion of the response signal from the OOFS active NFC device between times t3 and t4, the NFC reader 102 switches the frequency of the carrier signal to a non-standard frequency. The NFC reader 102 then listens for or receives the remainder of the response signal from the OOFS active NFC device between times t4 and t5. As Figure 3B shown, for the OOFS active NFC device 104C, the remainder of the response signal between times t4 and t5 is distorted. This is because the OOFS active NFC device 104C continues to output the response signal at the standard frequency while the NFC reader 102 is listening at the non-standard frequency. The result is a communication error where the NFC reader 102 does not correctly receive the remainder of the response from the OOFS active NFC device 104C.

[0077] Reference Figure 3B to graphs 304 and 306, between times t4 and t5, the remainder of the responses from the IFS active NFC device 104B (graph 304) and the passive device 104A (graph 306) are received without error. By comparison with Figure 3BFor an associated process, the NFC reader 102 can determine whether the NFC device is an OOFS active NFC device.

[0078] In one example, Figure 3B the distance between the non-standard frequency and the standard frequency is between 100 kHz and 300 kHz. The non-standard frequency can be higher or lower than the standard frequency. If the standard frequency is 13.56 MHz, the non-standard frequency can be between 13.66 MHz and 13.86 MHz, or between 13.26 MHz and 13.46 MHz. Without departing from the scope of the present disclosure, Figure 3B the non-standard frequency of can have other values than these values.

[0079] Figure 3C represents a situation where the NFC reader 102 adjusts the frequency of the carrier signal after the start of receiving the response signal. In Figure 3C , the NFC reader 102 adjusts the frequency of the carrier signal from the standard frequency to a non-standard frequency at which the response signals from the OOFS active NFC device 104C and the IFS active NFC device 104B cannot be reliably received, but the response signal from the passive NFC device 104A can be reliably received without error.

[0080] Between times t0 and t4, the operation of the NFC reader 102 is the same as the operation described with respect to Figure 3A . Referring to Figure 3C curves 302 and 304, curves 302 and 304 correspond to communication with the OOFS active NFC device 104C and communication with the IFS active NFC device 104B. After the NFC reader 102 receives the initial portion of the response signal between times t3 and t4, the NFC reader 102 switches the frequency of the carrier signal to the non-standard frequency. The NFC reader 102 then listens for or receives the remaining portion of the response signal between times t4 and t5. As Figure 3C shown, for the OOFS active NFC device 104C and the IFS active NFC device 104B, the remaining portion of the response signal between times t4 and t5 is distorted. The result is a communication error where the NFC reader 102 does not correctly receive the remaining portion of the response from the OOFS active NFC device 104C and the IFS active NFC device 104B.

[0081] Referring to Figure 3B curve 306, between times t4 and t5, the remaining response of the passive device 104A is received without error. For an associated process with Figure 3B , the NFC reader 102 can determine whether the NFC device is an OOFS active NFC device.

[0082] In one example, Figure 3C the distance between the non-standard frequency and the standard frequency of Figure 3C is between 500 kHz and 900 kHz. The non-standard frequency can be higher or lower than the standard frequency. If the standard frequency is 13.56 MHz, the non-standard frequency can be between 14.06 MHz and 14.46 MHz, or between 12.66 MHz and 13.06 MHz. Without departing from the scope of the present disclosure, Figure 3C the non-standard frequency of Figure 3C can have other values than these. In one embodiment, the non-standard frequency can have a range between 5 MHz and 25 MHz.

[0083] Figure 4 is a flowchart of a method 400 for operating an NFC reader according to one embodiment. Method 400 can utilize the systems, components, and processes described with respect to Figures 1 - 3C . Referring to Figure 4 and Figures 1 - 3C , at 402, the NFC reader 102 activates the carrier field. In one example, this can correspond to Figure 3C the time t0 - t1 in

[0084] At 404, the NFC reader 102 sends an interrogation signal. Sending or transmitting the interrogation signal corresponds to modulating the carrier signal with the NFC reader 102. In one example, this can correspond to Figure 3C the time t1 - t2 in

[0085] At 406, the NFC reader 102 receives the start of a response signal from the NFC device 104. The response signal can be an identification signal identifying the NFC device 104. In one example, the initial portion of the response signal can correspond to Figure 3B the time t2 - t3 in

[0086] If the start of the response signal is received at 406, the process proceeds to 408. If the start of the response signal is not received at 406, the process returns to 404. Figure 4 In Figure 3B , the non-standard NFC frequency is selected such that a passive NFC device can still provide an error-free response, but an active NFC device will not be able to provide an error-free response. The period during which the non-standard frequency is used can correspond to

[0087] At 410, the NFC reader 102 determines whether the entirety of the response signal has been received without error. In particular, the NFC reader 102 determines whether the remaining portion of the response signal has been received without error. If there is no error in receiving the remaining portion of the response signal, the process proceeds to 412. If there is an error in receiving the remaining portion of the response, the process proceeds to 414. At 412, the NFC reader 102 determines that the NFC device 104 is a passive NFC device. At 414, the NFC reader determines that the NFC device 104 is an active NFC device.

[0088] In one embodiment, if an active NFC device is detected and no passive NFC device is detected, the NFC reader 102 activates a charging field. The charging field can be used by the active NFC device to recharge the battery of the active NFC device.

[0089] Figure 5 is a flowchart of a process 500 for operating an NFC reader according to one embodiment. The method 500 can utilize the systems, components, and processes described with respect to Figures 1 - 3C Reference Figure 5 and Figures 1 - 3C , at 502, the NFC reader 102 activates a carrier field.

[0090] At 504, the NFC reader 102 sends an interrogation signal. Sending or transmitting the interrogation signal corresponds to modulating the carrier signal with the NFC reader 102. At 506, the NFC reader 102 receives the start of a response signal from the NFC device 104. The response signal can be an identification signal identifying the NFC device 104. If the start of the response signal is received at 506, the process proceeds to 508. If the start of the response signal is not received at 506, the process returns to 404.

[0091] At 508, the NFC reader 102 adjusts the frequency of the carrier signal while receiving the response signal. Adjusting the frequency can correspond to changing from a standard NFC frequency to a first non-standard NFC frequency. In Figure 5 , the first non-standard NFC frequency is selected such that IFS active NFC devices and passive NFC devices can still provide error-free responses, but OOFS active NFS devices will not be able to provide error-free responses.

[0092] At 510, the NFC reader 102 determines whether the entirety of the response signal has been received with error. If there is an error in receiving the remaining portion of the response, the process proceeds to 512. If there is no error in receiving the remaining portion of the response signal, the process proceeds to 514. At 512, the NFC reader 102 determines that the NFC device 104 is an OOFS active NFC device.

[0093] At 514, the NFC reader 102 adjusts the frequency of the carrier signal while receiving the response signal. Adjusting the frequency can correspond to changing from a standard NFC frequency to a second non-standard NFC frequency. In Figure 5 , the second non-standard NFC frequency is selected such that the passive NFC device can still provide an error-free response, but the IFS active NFC device will not be able to provide an error-free response. In practice, steps 504 - 510 occur in the first frame. Step 514 occurs in the second frame after the first frame. Before step 514, the second frame can include repeating steps 502 - 506 for the second frame.

[0094] At 516, the NFC reader 102 detects whether the entire response signal is received without error. In particular, the NFC reader 102 determines whether the remaining part of the response signal in the second frame is received without error. If there is an error when receiving the remaining part of the response, the process proceeds to 518. If there is no error when receiving the remaining part of the response signal and the second frame, the process proceeds to 520. At 520, the NFC reader 102 determines that the NFC device 104 is a passive NFC device. At 518, the NFC reader determines that the NFC device 104 is an IFS active NFC device.

[0095] In step 512 or 518, if the passive NFC device is not detected, the NFC reader 102 can activate the charging field to charge the OOFS active NFC device 104C or the IFS active NFC device 104B.

[0096] Figure 6 is a flowchart of a method 600 for operating an NFC reader according to an embodiment. Method 600 can utilize the systems, components, and processes described with respect to Figures 1 - 3C . Referring to Figure 6 and Figures 1 - 3C , at 602, the NFC reader 102 activates the carrier field.

[0097] At 604, the NFC reader 102 sends an interrogation signal. Sending or transmitting the interrogation signal corresponds to modulating the carrier signal with the NFC reader 102.

[0098] At 606, the NFC reader 102 receives the start of the response signal from the NFC device 104. The response signal can be an identification signal identifying the NFC device 104. In one example, the initial part of the response signal can correspond to Figure 3B the time t2 - t3 in

[0099] At 608, the NFC reader 102 adjusts the frequency of the carrier signal while receiving the response signal. Adjusting the frequency can correspond to changing from a standard NFC frequency to a non-standard NFC frequency.

[0100] At 610, the NFC reader 102 analyzes the frequency distribution of the remainder of the response signal. This can include detecting the intensities of various frequencies in the response signal.

[0101] At 612, the NFC reader 102 identifies whether there is a defect in the original standard NFC frequency in the remainder of the response signal. If the standard NFC frequency is a strong component of the remainder of the signal, the process proceeds to 614. If the standard NFC frequency is not a strong component of the remainder of the signal, the process proceeds to 616.

[0102] At 614, the NFC reader 102 determines that the NFC device is an OOFS active NFC device. At 616, the NFC reader 102 determines that the NFC device is an IFS active NFC device or a passive NFC device. At step 616, additional steps or processes can be performed to distinguish between an IFS NFC device and a passive NFC device. These can include identifying various other vacancy components of the response signal. Alternatively, the steps of process 400 can be performed. Figure 4 of

[0103] Figure 7 is a flowchart of a method 700 for operating an NFC reader according to one embodiment. Method 700 can utilize the systems, components, and processes described with respect to Figures 1 - 3C Reference Figure 7 and Figures 1 - 3C At 702, the NFC reader 102 activates a carrier field with a non-standard frequency.

[0104] At 704, the NFC reader 102 sends an interrogation signal. Sending or transmitting the interrogation signal corresponds to modulating the carrier signal with the NFC reader 102.

[0105] At 706, the NFC reader 102 receives the start of a response signal from the NFC device 104. The response signal can be an identification signal identifying the NFC device 104. If the start of the response signal is received at 706, the process proceeds to 708. If the start of the response signal is not received at 706, the process returns to 704.

[0106] At 708, the NFC reader 102 analyzes the frequency distribution of the remainder of the response signal. This can include detecting the intensities of various frequencies in the response signal.

[0107] At 710, the NFC reader 102 identifies whether the original standard NFC frequency is detected in the remainder of the response signal. If the standard NFC frequency is not a strong component of the remainder of the signal, the process proceeds to 712. If the standard NFC frequency is a strong component of the remainder of the signal, the process proceeds to 714.

[0108] At 714, the NFC reader 102 determines that the NFC device is an OOFS active NFC device. At 712, the NFC reader 102 determines that the NFC device is an IFS active NFC device or a passive NFC device. At step 712, additional steps or processes may be performed to distinguish between an IFS active NFC device and a passive NFC device. These may include identifying various other frequency components of the response signal. Alternatively, the steps of Figure 4 process 400 may be performed.

[0109] Figure 8 is a flow chart of a method 800 for operating an NFC reader according to one embodiment. At 802, method 800 includes transmitting a carrier signal from a near field communication reader. At 804, method 800 includes transmitting an interrogation signal with the carrier signal. At 806, method 800 includes receiving a portion of a response signal from a near field communication device in response to the interrogation signal. At 808, method 800 includes adjusting the frequency of the carrier signal for a selected duration after receiving a portion of the response signal and before receiving the entire response signal. At 810, method 800 includes receiving the remainder of the response signal. At 812, method 800 includes: based on the remainder of the response signal, determining whether the near field communication device is a passive near field communication device or an active load modulation near field communication device.

[0110] Figure 9Schematic diagram of the circuitry of an NFC reader 102 according to one embodiment. The NFC reader 102 includes an NFC antenna coil 902, a wireless charging antenna coil 904, and a reader control system 113. The NFC antenna coil 902 is part of an RF transceiver 111 through which the NFC reader 102 enables NFC communication with NFC devices. The wireless charging coil 904 is part of a wireless charging circuitry 112 through which the NFC reader 102 or an electronic device of which the NFC reader 102 is a part provides a wireless charging field. In one embodiment, the reader control system 113 controls the RF antenna coil and the wireless charging coil. Parts of the wireless charging circuitry 112 may be included in the reader control system 113. Alternatively, the wireless charging circuitry 112 may be controlled by a separate control system. In one embodiment, the wireless charging antenna coil 904 is a wireless charging coil compliant with the Qi standard. However, without departing from the scope of the present disclosure, the charging antenna coil 904 may utilize other charging standards than Qi. Further, without departing from the scope of the present disclosure, the number and configuration of the antenna coils may be different from Figure 9 that shown.

[0111] Figure 10 Schematic diagram of an NFC communication system 1000 according to one embodiment. The NFC communication system 1000 includes an NFC reader 102, a passive NFC device 104A, and active NFC devices 104B (IFS) or 104C (OOFS). The NFC reader 102 communicates with the active NFC devices 104B / 104C and the passive NFC device 104A.

[0112] In Figure 10 an example, the active NFC devices 104B / 104C are smart phones having active NFC circuitry. In Figure 10 an example, the passive NFC device 104A is a credit card having passive NFC circuitry. The smart phone includes a protective case 1002. The protective case 1002 includes a plurality of slots for accommodating various types of cards. The credit card is positioned in one of the slots of the protective case 1002. This is a common configuration that enables people to carry an identification card and a credit card with the smart phone.

[0113] The NFC reader 102 includes a charging cradle 110. A user can place the smart phone 104B / 104C on the charging cradle. The NFC reader 102 can communicate with the smart phone 104 via the NFC protocol. When the smart phone is located on the charging cradle 110, the NFC reader 102 can charge the battery of the smart phone.

[0114] Because credit card 104A is a passive NFC device that includes a passive NFC circuit device, a fully powered charging field may damage the NFC circuit device of credit card 104A. Thus, when credit card 104A is located within protective case 1002 of smart phone 104B / 104C and smart phone 104B / 104C is located on charging stand 110, a fully powered charging field may damage the NFC circuit device of credit card 104A.

[0115] When smart phone 104B / 104C is positioned on charging stand 110, NFC reader 102 outputs an interrogation signal and listens for responses for various NFC protocols. In this way, NFC reader 102 establishes communication with both smart phone 104B / 104C and credit card 104A.

[0116] After identifying both smart phone 104B / 104C and credit card 104A, NFC reader 102 performs a process for finally determining the NFC types of both smart phone 104B / 104C and credit card 104A. In particular, NFC reader 102 transmits an interrogation signal using the protocol of smart phone 104B / 104C. When NFC reader 102 receives the start of an identification or response signal from smart phone 104B / 104C, NFC reader 102 adjusts the frequency of the carrier signal. During the adjustment of the frequency of the carrier signal, NFC reader 102 listens for the identification signal. In one example, NFC reader 102 detects the presence of both credit card 104A and smart phone 104B / 104C. Because the NFC reader has detected the presence of both a passive NFC device and an active NFC device, wireless charging circuit device 112 outputs a charging field having a reduced amplitude or power. The power of the charging field is selected such that it will not damage the NFC circuit device of credit card 104A. The charging field charges the battery of smart phone 104B / 104C.

[0117] If NFC reader 102 only detects an active NFC device, wireless charging circuit device 112 may output a fully powered charging field to charge the battery of the active NFC device. If the NFC reader only detects a passive NFC device, wireless charging circuit device 112 will not output any charging field.

[0118] Figure 10 An embodiment is shown where the active NFC device is a smart phone and the passive NFC device is an NFC-enabled credit card. However, other types of active and passive NFC devices may be used without departing from the scope of the present disclosure.

[0119] In one embodiment, a method includes transmitting a carrier signal from a near field communication (NFC) reader, transmitting an interrogation signal with the carrier signal, and receiving an initial portion of a response signal from an NFC device in response to the interrogation signal. The method includes adjusting a frequency of the carrier signal after receiving the initial portion of the response signal and before receiving all of the response signal, receiving a remaining portion of the response signal, and determining, based on the remaining portion of the response signal, whether the NFC device is a passive load modulation NFC device or an active load modulation NFC device.

[0120] In one embodiment, a method includes transmitting a carrier signal from an NFC reader, transmitting an interrogation signal with the carrier signal, and receiving an initial portion of a response signal from an NFC device in response to the interrogation signal. The method includes adjusting a frequency of the carrier signal after receiving the initial portion of the response signal and before receiving all of the response signal, receiving a remaining portion of the response signal, and determining, based on the remaining portion of the response signal, whether the NFC device is a first type of active load modulation NFC device or a second type of active load modulation device.

[0121] In one embodiment, a method includes transmitting a first interrogation signal from an NFC reader with a carrier signal during a first NFC communication frame, adjusting a frequency of the carrier signal from a first frequency to a second frequency during the first NFC communication frame, and receiving a first response signal from the NFC device during the first NFC communication frame. The method includes transmitting a second interrogation signal with the carrier signal during a second NFC communication frame after the first NFC communication frame, adjusting the frequency of the carrier signal from the first frequency to a third frequency during the second NFC communication frame, receiving a second response signal from the NFC device with the NFC reader during the second NFC communication frame, and determining, based on the first response signal and the second response signal, whether the NFC device is an in-frame synchronous active load modulation NFC device, an out-of-frame synchronous active load modulation NFC device, or a passive load modulation NFC device.

[0122] In one embodiment, a method includes transmitting a carrier signal from an NFC reader and adjusting a frequency of the carrier signal during an NFC communication frame. The method includes receiving a response signal from the NFC device with the NFC reader during the NFC communication frame and determining, based on the response signal, whether the NFC device is a passive load modulation NFC device or an active load modulation NFC device.

[0123] In one embodiment, a method includes transmitting a carrier signal from a near field communication (NFC) reader, transmitting an interrogation signal with the carrier signal, and receiving an initial portion of a response signal from an NFC device in response to the interrogation signal. The method includes adjusting a frequency of the carrier signal from a first frequency to a second frequency after receiving the initial portion of the response signal and before receiving the entire response signal, receiving a remaining portion of the response signal, and identifying a type of the NFC device by analyzing a frequency of the remaining portion of the response signal.

[0124] In one embodiment, a method includes transmitting a carrier signal having a non-standard frequency for NFC from an NFC reader, and transmitting an interrogation signal with the carrier signal. The method includes receiving a response signal from an NFC device, and identifying a type of the NFC device by analyzing a frequency of the response signal.

[0125] In one embodiment, an NFC reader includes a radio frequency transceiver configured to transmit and receive NFC signals and a control system coupled to the radio frequency transceiver. The control system is configured to cause the radio frequency transceiver to output an interrogation signal, output a carrier signal, and adjust a frequency of the carrier signal in response to receiving an initial portion of a response signal from an NFC device.

[0126] In one embodiment, an NFC reader includes a radio frequency transceiver configured to transmit and receive NFC signals and a control system coupled to the radio frequency transceiver. The control system is configured to cause the radio frequency transceiver to adjust a frequency of the carrier signal from a first frequency to a second frequency while receiving a first response signal from an NFC device during a first frame, adjust the frequency of the carrier signal from the first frequency to a third frequency while receiving a second response signal from the NFC device during a second frame, and determine whether the NFC device is an in-frame synchronous active load modulation NFC device, an out-of-frame synchronous active load modulation NFC device, or a passive load modulation NFC device based on the first response signal and the second response signal.

[0127] In one embodiment, an NFC reader includes a radio frequency transceiver configured to transmit and receive NFC signals and a control system coupled to the radio frequency transceiver. The control system is configured to cause the radio frequency transceiver to transmit a carrier signal, adjust a frequency of the carrier signal from a first frequency to a second frequency during an NFC frame, and receive a response signal from an NFC device during the NFC frame. The control system is configured to determine whether the NFC device is a passive load modulation NFC device or an active load modulation NFC device based on a frequency of the response signal.

[0128] In one embodiment, a near field communication reader includes a radio frequency transceiver configured to transmit and receive near field communication signals and a control system coupled to the radio frequency transceiver. The control system is configured to cause the radio frequency transceiver to transmit a carrier signal from the near field communication reader at a non-standard frequency for near field communication, transmit an interrogation signal with the carrier signal, and receive a response signal from the near field communication device, wherein the control system is configured to identify the type of the near field communication device by analyzing the frequency of the response signal.

[0129] The various embodiments described above may be combined to provide additional embodiments. These and other changes may be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed as limiting the claims to the specific embodiments disclosed in the specification and the claims, but should be understood to include all possible embodiments and the full scope of equivalents to which these claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

1. A method, comprising: Transmitting a carrier signal from a near - field communication reader; Transmitting an interrogation signal with the carrier signal; Receiving an initial portion of a response signal from a near - field communication device in response to the interrogation signal; Adjusting the frequency of the carrier signal after receiving the initial portion of the response signal and before receiving the entire response signal; Receiving the remaining portion of the response signal; and Determining, based on the remaining portion of the response signal, whether the near - field communication device is a passive load - modulation near - field communication device or an active load - modulation near - field communication device.

2. The method according to claim 1, wherein adjusting the frequency comprises adjusting the frequency from a standard near - field communication frequency to a non - standard near - field communication frequency.

3. The method according to claim 2, wherein the standard near - field communication frequency is 13.56 MHz.

4. The method according to claim 1, further comprising determining whether the near - field communication device is a passive load - modulation near - field communication device or an active load - modulation device based on whether the remaining portion of the response signal includes an error.

5. The method according to claim 4, further comprising: If the remaining portion of the response signal includes an error, determining that the near - field communication device is an active load - modulation near - field communication device; And If the remaining portion of the response signal does not include an error, determining that the near - field communication device is a passive load - modulation near - field communication device.

6. The method according to claim 5 further comprises: If the near - field communication device is an active load - modulation near - field communication device, outputting a charging signal from the near - field communication reader.

7. A method, comprising: Transmitting a carrier signal from a near - field communication reader; Transmitting an interrogation signal with the carrier signal; Receiving an initial portion of a response signal from a near - field communication device in response to the interrogation signal; Adjusting the frequency of the carrier signal after receiving the initial portion of the response signal and before receiving the entire response signal; Receiving the remaining portion of the response signal; and Determining, based on the remaining portion of the response signal, whether the near - field communication device is a first type of active load - modulation near - field communication device or a second type of active load - modulation device.

8. The method according to claim 7, wherein the first type of active load - modulation device is an in - frame synchronous active load - modulation near - field communication device.

9. The method according to claim 8, wherein the second type of active load - modulation device is an out - of - frame synchronous active load - modulation near - field communication device.

10. The method according to claim 9, further comprising: Determining whether the remaining portion of the response signal includes an error; If the remaining portion of the response signal includes an error, determining that the near - field communication device is an out - of - frame synchronous active load - modulation near - field communication device; And If the remaining portion of the response signal does not include an error, determining that the near - field communication device is an in - frame synchronous active load - modulation near - field communication device.

11. A method, comprising: During a first near - field communication frame, transmitting a first interrogation signal from a near - field communication reader with a carrier signal; During the first near field communication frame, adjust the frequency of the carrier signal from a first frequency to a second frequency; During the first near field communication frame, receive a first response signal from a near field communication device; During a second near field communication frame after the first near field communication frame, transmit a second interrogation signal with the carrier signal; During the second near field communication frame, adjust the frequency of the carrier signal from the first frequency to a third frequency; During the second near field communication frame, receive a second response signal from a near field communication device with the near field communication reader; And Based on the first response signal and the second response signal, determine whether the near field communication device is an in-frame synchronous active load modulation near field communication device, an out-of-frame synchronous active load modulation near field communication device, or a passive load modulation near field communication device.

12. The method according to claim 11, wherein adjusting the frequency during the first frame includes adjusting the frequency after receiving a part of the first response signal.

13. The method according to claim 12, wherein adjusting the frequency during the second frame includes adjusting the frequency after receiving a part of the second response signal.

14. The method according to claim 13, wherein the difference between the first frequency and the second frequency is greater than the difference between the first frequency and the third frequency, and the method further includes: Based on the first response signal, determine whether the near field communication device is an out-of-frame active load modulation near field communication device; And Based on the second response signal, determine that the near field communication device is an in-frame synchronous active load modulation device or a passive load modulation near field communication device.

15. The method according to claim 13, wherein the difference between the first frequency and the second frequency is less than the difference between the first frequency and the third frequency, and the method further includes: Based on the first response signal, determine whether the near field communication device is a passive load modulation near field communication device; And Based on the second response signal, determine that the near field communication device is an in-frame synchronous active load modulation device or an out-of-frame synchronous passive load modulation near field communication device.

16. A method, comprising: Transmit a carrier signal from a near field communication reader; During a near field communication frame, adjust the frequency of the carrier signal; During the near field communication frame, receive a response signal from a near field communication device with the near field communication reader; And Based on the response signal, determine whether the near field communication device is a passive load modulation near field communication device or an active load modulation near field communication device.

17. The method according to claim 16, wherein adjusting the frequency during the frame includes adjusting the frequency after receiving a part of the response signal.

18. The method according to claim 17, wherein adjusting the frequency includes adjusting the frequency by more than 500 KHz.

19. A method, comprising: Transmit a carrier signal from a near field communication reader; Transmit an interrogation signal with the carrier signal; Receive an initial part of a response signal from a near field communication device in response to the interrogation signal; After receiving the initial portion of the response signal and before receiving all of the response signal, adjust the frequency of the carrier signal from a first frequency to a second frequency; Receive the remaining portion of the response signal; And Identify the type of the near field communication device by analyzing the frequency of the remaining portion of the response signal.

20. The method according to claim 19, the method further comprising: If the frequency of the remaining portion of the response signal is the first frequency, determine that the near field communication device is an out-of-frame synchronization device.

21. The method according to claim 20, wherein the first frequency is a standard near field communication frequency.

22. A method, comprising: Transmit a carrier signal having a non-standard frequency for near field communication from a near field communication reader; Transmit an interrogation signal with the carrier signal; Receive a response signal from a near field communication device; And Identify the type of the near field communication device by analyzing the frequency of the response signal.

23. The method according to claim 22, wherein the method further comprises: If the frequency of the response signal is a standard near field communication frequency different from the non-standard near field communication frequency, determine that the near field communication device is an out-of-frame synchronization active load modulation near field communication device.

24. The method according to claim 22 further comprises: Based on the frequency of the response signal, determine that the near field communication device is a passive load modulation near field communication device or an in-frame synchronization active load modulation near field communication device.

25. A near field communication reader, comprising: A radio frequency transceiver configured to transmit and receive near field communication signals; And A control system coupled to the radio frequency transceiver and configured to cause the radio frequency transceiver to output an interrogation signal, output a carrier signal, and adjust the frequency of the carrier signal in response to receiving an initial portion of a response signal from a near field communication device, wherein the radio frequency transceiver is configured to receive the remaining portion of the response signal after adjusting the frequency, and wherein the control system is configured to: based on the remaining portion of the response signal, determine that the near field communication device is an active near field communication device or a passive near field communication device.

26. The near field communication reader according to claim 25, further comprising a memory including software instructions for determining that the near field communication device is an active near field communication device or a passive near field communication device.

27. The near field communication reader according to claim 26, wherein the control system includes one or more processors communicatively coupled to the memory and configured to execute the software instructions.

28. The near field communication reader according to claim 25, further comprising a wireless charging circuitry separate from the radio frequency transceiver, wherein the control system is configured to: if the near field communication device is an active near field communication device, cause the wireless charging circuitry to output a charging field to recharge the battery of the near field communication device.

29. The near field communication reader according to claim 28, wherein the control system is configured to: if there is also a passive near field communication device, cause the wireless charging circuitry to output a reduced charging field to recharge the battery of the near field communication device.

30. The near field communication reader according to claim 28, wherein the wireless charging circuit device operates according to the Qi standard for wireless charging.

31. The near field communication reader according to claim 30, wherein the wireless charging field has a frequency between 87 KHz and 205 KHz, and wherein the radio frequency transceiver communicates between 5 MHz and 25 MHz.

32. The near field communication reader according to claim 25, wherein the radio frequency transceiver is configured to receive the remaining portion of the response signal after adjusting the frequency, and wherein the control system is configured to: based on the remaining portion of the response signal, determine whether the near field communication device is an in-frame synchronous active load modulation near field communication device or an out-of-frame active load modulation near field communication device.

33. A near field communication reader, comprising: a radio frequency transceiver configured to transmit and receive near field communication signals; and a control system coupled to the radio frequency transceiver and configured to cause the radio frequency transceiver to adjust the frequency of a carrier signal from a first frequency to a second frequency while receiving a first response signal from a near field communication device during a first frame, and to adjust the frequency of the carrier signal from the first frequency to a third frequency while receiving a second response signal from the near field communication device during a second frame, and to determine, based on the first response signal and the second response signal, whether the near field communication device is an in-frame synchronous active load modulation near field communication device, an out-of-frame synchronous active load modulation near field communication device, or a passive load modulation near field communication device.

34. The near field communication reader according to claim 33, wherein the difference between the first frequency and the second frequency is greater than the difference between the first frequency and the third frequency, and wherein the control system is configured to determine whether the near field communication device is an out-of-frame synchronous active load modulation near field communication device based on the first response signal, and to determine whether the near field communication device is an in-frame synchronous active load modulation device or a passive load modulation near field communication device based on the second response signal.

35. The near field communication reader according to claim 33, wherein the difference between the first frequency and the second frequency is less than the difference between the first frequency and the third frequency, and wherein the control system is configured to determine whether the near field communication device is a passive load modulation near field communication device based on the first response signal, and is further configured to determine whether the near field communication device is an in-frame synchronous active load modulation device or an out-of-frame synchronous passive load modulation near field communication device based on the second response signal.

36. A near field communication reader, comprising: a radio frequency transceiver configured to transmit and receive near field communication signals; and A control system, coupled to the radio frequency transceiver and configured to cause the radio frequency transceiver to transmit a carrier signal, adjust the frequency of the carrier signal from a first frequency to a second frequency during a near field communication frame, and receive a response signal from a near field communication device during the near field communication frame, wherein the control system is configured to determine whether the near field communication device is a passive load modulation near field communication device or an active load modulation near field communication device based on the frequency of the response signal.

37. The near field communication reader according to claim 36, wherein the control system is configured to: determine that the near field communication device is an out-of-frame synchronization device if the frequency of the response signal is the first frequency.

38. The near field communication reader according to claim 37, wherein the first frequency is a standard near field communication frequency.

39. A near field communication reader, comprising: a radio frequency transceiver configured to transmit and receive near field communication signals; and a control system coupled to the radio frequency transceiver and configured to cause the radio frequency transceiver to transmit a carrier signal from the near field communication reader at a non-standard frequency for near field communication, transmit an interrogation signal with the carrier signal, and receive a response signal from a near field communication device, wherein the control system is configured to identify the type of the near field communication device by analyzing the frequency of the response signal.

40. The near field communication reader according to claim 39, wherein the control system is configured to: determine that the near field communication device is an out-of-frame synchronization active load modulation near field communication device if the frequency of the response signal is a standard near field communication frequency different from the non-standard near field communication frequency.

41. The near field communication reader according to claim 39, further comprising determining whether the near field communication device is a passive load modulation near field communication device based on the frequency of the response signal.

Images