NFC passive tag identification and NFC device

Abstract

An NFC passive tag identification system and method, and an NFC device. The NFC passive tag identification system comprises an energy harvesting circuit used for harvesting and storing ambient energy. The NFC passive tag identification system further comprises a radio frequency sending circuit that is connected to the energy harvesting circuit, powered by the ambient energy, and used for sending an excitation signal for enabling a terminal device to exit a low power card detection (LPCD) mode. In addition, the NFC passive tag identification system further comprises an NFC tag circuit used for sensing an NFC detection signal sent by the terminal device so as to communicate with the terminal device.

Description

NFC passive tag identification and NFC devices Technical Field

[0001] The embodiments in this specification generally relate to the field of Near Field Communication (NFC) technology, and more specifically to an NFC passive tag identification system, method and NFC device. Background Technology

[0002] NFC, or Near Field Communication, is a short-range, high-frequency wireless technology evolved from contactless Radio Frequency Identification (RFID). It supports short-range wireless communication between mobile devices, consumer electronics, PCs, and smart control tools. It operates at a frequency of 13.56 MHz and has a transmission distance of 10 to 20 centimeters. As a wireless connectivity technology that provides easy, secure, and fast communication, NFC features short range, high bandwidth, and low power consumption.

[0003] NFC devices can be divided into passive NFC devices and active NFC devices. Passive NFC devices include NFC tags and other small transmitters. They can send information to other NFC devices without requiring a power source, thus offering advantages such as low cost, long lifespan, and strong environmental adaptability. Active NFC devices can send and receive data and can communicate with each other as well as with passive devices. Active NFC devices can only operate when powered. Summary of the Invention

[0004] In view of this, one or more embodiments of this specification provide an NFC passive tag identification system, method, and NFC device that can collect and store various ambient energies for transmitting carrier signals of the NFC radio frequency field, enabling nearby NFC card readers and other terminal devices to exit LPCD mode and communicate in normal card detection mode, thereby improving NFC tag identification efficiency in passive NFC scenarios with low power consumption and low cost.

[0005] In a first aspect of this specification, an NFC passive tag identification system is provided. The system includes an energy harvesting circuit for harvesting and storing ambient energy. The system also includes a radio frequency transmission circuit connected to the energy harvesting circuit and powered by the ambient energy for transmitting an excitation signal to cause a terminal device to exit a low-power card detection (LPCD) mode. Furthermore, the system includes an NFC tag circuit for sensing an NFC detection signal transmitted by the terminal device to communicate with the terminal device.

[0006] In a second aspect of this specification, an NFC passive tag identification method is provided. The method includes collecting and storing ambient energy. The method also includes, based on the ambient energy, sending an excitation signal to cause a terminal device to exit a low-power card detection (LPCD) mode. Furthermore, the method includes sensing an NFC probe signal sent by the terminal device to communicate with the terminal device.

[0007] In a third aspect of this specification, an NFC device is provided, which operates in passive mode and a terminal device communicating with the NFC device operates in active mode. The NFC device includes the system as described in the first aspect of this specification.

[0008] It should be understood that the description in the Summary of the Invention section is not intended to limit the key or essential features of the embodiments of this specification, nor is it intended to limit the scope of this disclosure. Other features of this specification will become readily apparent from the following description. Attached Figure Description

[0009] The above and other objects, features, and advantages of the embodiments of this specification will become more readily understood from the following detailed description with reference to the accompanying drawings. Several embodiments of this specification will be described by way of example and non-limitation in the drawings.

[0010] Figure 1 shows a schematic diagram of the structure of an NFC passive tag identification system according to some embodiments of this specification.

[0011] Figure 2 shows a schematic circuit layout of an NFC passive tag identification system according to some embodiments of this specification.

[0012] Figure 3A shows a schematic diagram of the structure of a radio frequency transmission circuit according to some embodiments of this specification.

[0013] Figure 3B shows an equivalent circuit diagram of a radio frequency transmission circuit according to some embodiments of this specification.

[0014] Figure 4A shows a schematic diagram of the structure of an NFC tag circuit according to some embodiments of this specification.

[0015] Figure 4B shows an equivalent circuit diagram of an NFC tag circuit according to some embodiments of this specification.

[0016] Figure 5 shows a flowchart of an NFC passive tag identification method according to some embodiments of this specification.

[0017] In all the accompanying figures, the same or similar reference numerals denote the same or similar elements. Detailed Implementation

[0018] Embodiments of this specification will now be described in more detail with reference to the accompanying drawings. While some embodiments of this specification are shown in the drawings, it should be understood that this specification can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this specification. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0019] In the description of embodiments in this specification, the term "comprising" and similar terms should be understood as open-ended inclusion, i.e., "including but not limited to". The term "based on" should be understood as "at least partially based on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc., may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0020] As mentioned above, NFC has gained increasing popularity across various industries in recent years due to its short-range, fast connection, low power consumption, and high compatibility, finding wide application in scenarios such as mobile payment, data exchange, and access control. Passive NFC tags are near-field communication devices that do not rely on their own power source. These tags exchange data via short-range wireless signals with NFC readers. When an NFC reader approaches a passive tag, the electromagnetic field emitted by the reader powers the tag, activating its built-in circuitry. The tag then transmits its stored data back to the reader via modulation, completing the data exchange.

[0021] Low Power Card Detection (LPCD) mode is a low-power card detection method that allows NFC readers to detect card proximity without continuous polling. This mode achieves this by periodically sending radio frequency (RF) pulses and monitoring reflected signals. When a signal change (such as detuning) is detected, it triggers the NFC reader to initiate further communication.

[0022] When identifying NFC tags, terminal devices with NFC card reading capabilities are typically in active mode, detecting the presence of nearby NFC devices by emitting an electric field. However, since terminal devices, especially mobile devices, are usually battery-powered, some devices automatically switch to LPCD mode after the screen is on for a period of time to extend battery life and improve battery performance. Once in LPCD mode, if the antenna coupling area is insufficient or the electric field change is not significant enough, the terminal device may have difficulty exiting this mode, thus hindering normal communication between the terminal device and the NFC tag, affecting the NFC identification success rate, and impacting the user experience.

[0023] Therefore, this specification provides an NFC passive tag identification system in its embodiments. This system can collect and store various ambient energies to transmit carrier signals for the NFC radio frequency field, causing nearby NFC card readers and other terminal devices to exit LPCD mode and communicate with NFC tags in normal card detection mode. This improves NFC identification efficiency in passive NFC scenarios with low cost and low power consumption.

[0024] Figure 1 shows a schematic diagram of the structure of an NFC passive tag identification system 100 according to some embodiments of this specification. As shown in Figure 1, the NFC passive tag identification system 100 may include an energy harvesting circuit 102, an radio frequency transmission circuit 104, and an NFC tag circuit 106.

[0025] The energy harvesting circuit 102 can harvest and store ambient energy from the surrounding environment to power the radio frequency transmitting circuit 104. Energy harvesting (EH) refers to the collection and utilization of available energy from the environment to power electrical or charging devices. Ambient energy includes, but is not limited to, radio frequency energy, thermal energy, and light energy. These energy sources are characterized by their universality, stability, and sustainability, thus serving as reliable sources for energy harvesting.

[0026] In some embodiments, radio frequency (RF) energy harvesting circuitry can be used to capture energy from RF signals and convert it into electrical energy. Specifically, an antenna can first be used to capture electromagnetic waves (RF signals) and convert them into electrical signals. Then, the alternating current (AC) signal captured by the antenna is converted into a direct current (DC) signal by a rectifier. Optionally, the rectifier can be implemented using devices such as diodes or metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0027] In some embodiments, a thermal energy harvesting circuit can also be used to capture thermal energy from the environment and convert it into electrical energy. Specifically, a thermopile consisting of multiple thermocouples connected in series can be used, which generates an electromotive force when a temperature difference is generated at its ends. Alternatively, the property of pyroelectric elements to generate charge when the temperature changes can also be utilized to convert the captured thermal energy into electrical energy.

[0028] In some embodiments, photovoltaic energy harvesting circuits can also be used to convert light energy into electrical energy using the photovoltaic effect. Specifically, photons can be used to excite electrons in a photovoltaic cell, thereby generating an electric current.

[0029] Because the collected ambient energy is usually weak and unstable, energy storage devices are needed to store and manage this energy. For example, capacitors or lithium-ion batteries can be used to store electrical energy converted from ambient energy.

[0030] In some embodiments, the energy harvesting circuit 102 may also be connected to a boost regulator circuit and an oscillator circuit. The boost regulator circuit can be used to increase the output voltage to meet the voltage requirements of the radio frequency (RF) transmitting circuit 104. The oscillator circuit can be used to generate a periodic voltage signal and send it to the RF transmitting circuit 104 so that the RF transmitting circuit 104 periodically transmits an excitation signal. Specifically, the ambient energy harvested by the energy harvesting circuit 102 can first be converted into a smooth and stable DC voltage by the boost regulator circuit, and then converted into an AC oscillation signal of a specific frequency by the oscillator circuit, and then sent to the RF transmitting circuit 104.

[0031] The radio frequency transmitting circuit 104 can transmit an excitation signal to cause the terminal device to exit the low-power card detection (LPCD) mode, based on the energy provided by the energy harvesting circuit 102. The energy provided by the energy harvesting circuit 102 can be the periodic voltage signal generated by the aforementioned oscillation circuit.

[0032] The aforementioned terminal devices with NFC card reading functionality include, but are not limited to, smartphones, smartwatches, and smart glasses. Since they are typically battery-powered, they are highly sensitive to power consumption. To control power consumption, they usually incorporate many low-power design features, such as setting up LPCD mode, in their card readers' transmission power. For example, most smartphones automatically switch to LPCD mode after the screen has been on for a period of time.

[0033] In practical applications, a mobile device will only wake up from LPCD mode and enter normal card reading mode when the terminal device detects that its emitted radio frequency signal is sensed by a nearby NFC target device, and the resulting signal strength change reaches or exceeds a preset threshold. However, in LPCD mode, the signal strength emitted by the terminal device is weakened, and the amplitude of the radio frequency signal is lower than in normal card reading mode. This causes the response amplitude of the NFC target device to the signal to decrease accordingly, making it difficult for the terminal device to accurately determine whether an NFC target device is nearby based on changes in signal amplitude. Therefore, the terminal device can be prompted to exit LPCD mode by actively emitting a stronger excitation signal.

[0034] In some embodiments, the radio frequency transmitting circuit 104 may include a first NFC chip connected to the energy harvesting circuit 102 and an excitation coil connected to the first NFC chip. The first NFC chip may receive an AC oscillation signal generated by the energy harvesting circuit 102 as described above, modulate it onto a carrier signal (i.e., an excitation signal) containing a specified data packet (including but not limited to commands such as card search, P2P transmission, etc.), and send it to the excitation coil. The excitation coil may then transmit the excitation signal to form a radio frequency field around the system. Optionally, the excitation signal may also be an empty carrier signal without any information to reduce the system burden of transmitting signals. The first NFC chip may be any NFC chip supporting the 13.56MHz carrier standard. The first NFC chip and the excitation coil described above may be provided by commercially available chips, and this specification does not limit this.

[0035] The NFC tag circuit 106 can sense NFC detection signals sent by a terminal device to communicate with the terminal device. The NFC tag circuit 106 may include a second NFC chip and an NFC coil. Specifically, the NFC coil can receive NFC detection signals from the terminal device and simultaneously generate an electromagnetic induction current for the second NFC chip to receive and send data. Similarly, since the 13.56MHz communication carrier frequency of NFC technology has been standardized globally, the second NFC chip can be any NFC chip supporting the 13.56MHz carrier standard. The aforementioned second NFC chip and NFC coil can be provided by commercially available chips, and this specification does not impose any limitations on this.

[0036] In different scenarios, the second NFC chip can contain different information. For example, in a payment scenario, the second NFC chip can contain payment order information. In a food ordering scenario, the second NFC chip can contain menu and seating information. And in an access control scenario, the second NFC chip can contain authentication information.

[0037] It should be understood that the architecture and functionality of System 100 are described for illustrative purposes only and do not imply any limitation on the scope of this specification. Embodiments of this specification can also be applied to other environments with different structures and / or functionalities.

[0038] The process according to the embodiments of this specification will be described in detail below with reference to Figures 2 to 5. For ease of understanding, the specific data mentioned in the following description are exemplary and are not intended to limit the scope of this disclosure. It should be understood that the embodiments described below may also include additional actions not shown and / or actions shown may be omitted, and the scope of this disclosure is not limited in this respect.

[0039] Since this system involves two NFC coil circuits, where the radio frequency transmitting circuit 104 transmits a carrier signal of the radio frequency field through an external power supply to enable the terminal device to exit LPCD mode, and the NFC tag circuit 106 generates electricity by itself, stores information and responds to the NFC detection signal of the terminal device, the circuit layout should avoid interference when the terminal device receives the excitation signal and reads the data stored in the NFC tag circuit.

[0040] Figure 2 shows a schematic diagram of the structure of an NFC passive tag identification system 200 according to some embodiments of this specification. As shown in Figure 2, the radio frequency transmission circuit 104 and the NFC tag circuit 106 can be arranged overlappingly in the same plane. The radio frequency transmission circuit 104 may include a first NFC chip 204 and an excitation coil 206, with the excitation coil 206 arranged on the outermost side. The first NFC chip 204 can be powered by the energy harvesting circuit 202 through a positive voltage supply terminal VDD and a ground terminal VSS. The NFC tag circuit 106 may include a second NFC chip 208 and an NFC coil 210. The NFC tag circuit 106 is located inside the excitation coil 206. In this way, signal interference can be avoided as much as possible.

[0041] In some embodiments, the radio frequency transmitting circuit 104 and the NFC tag circuit 106 can be arranged vertically or horizontally, etc. This specification does not limit the specific circuit layout.

[0042] Figure 3A shows a schematic diagram of the structure of a radio frequency (RF) transmitting circuit 300 according to some embodiments of this specification. As shown in Figure 3A, the RF transmitting circuit 300 may include a first NFC chip 302, a first low-pass filter 304, a first matching circuit 306, a first current-limiting element 308, and an excitation coil 310. The energy harvesting circuit 202 can supply power to the first NFC chip 302 through a positive voltage supply terminal VDD and a ground terminal VSS, for example, by providing a periodic AC oscillation signal. The first low-pass filter 304 may include an inductor and a capacitor, and utilizes its characteristic of allowing only signals below the cutoff frequency to pass through while blocking signals above the cutoff frequency to filter out high-order harmonics of the crystal oscillator, thereby improving the stability of signal transmission.

[0043] The first matching circuit 306 can be tuned with the excitation coil 310 to adjust the impedance parameters and resonant frequency parameters. The first current-limiting element 308 may include a series resistor, which can adjust the balance between the quality factor (Q value) of the excitation coil 310 and the bandwidth of the circuit. The Q value reflects the coil's losses at the resonant frequency and is inversely proportional to the circuit bandwidth. The excitation coil 310 can send an excitation signal to excite the terminal device to exit LPCD mode.

[0044] Figure 3B shows an equivalent circuit diagram of a radio frequency transmission circuit according to some embodiments of this specification. As shown in Figure 3B, the first NFC chip 302 can be represented as chip IC1 for signal modulation and demodulation and data reception and transmission. The oscillating AC signal of the energy harvesting circuit 202 flows in from the positive terminal VDD of the power supply, passes through the components, and flows out from the ground VSS, forming a loop. Chip IC1 may include multiple pins, such as pin Rx for receiving external data, a transient voltage suppressor Tvss to ground to prevent circuit damage due to transient overvoltages (such as lightning strikes, electrostatic discharge, etc.), and differential signal transmission pins Tx+ and Tx- for high-speed, interference-resistant data transmission.

[0045] As shown in Figure 3B, the first low-pass filter 304 can be composed of an inductor L0 and a capacitor C0 to filter out high-order harmonics of the crystal oscillator. Capacitors C1 and C2 can form a first matching circuit 306 to adjust the impedance parameters and resonant frequency parameters. Resistor R1 can serve as a first current-limiting element 308 to adjust the Q value of coil ANT1, i.e., the excitation coil 310, and the bandwidth of the circuit.

[0046] Figure 4A shows a schematic diagram of the structure of an NFC tag circuit 400 according to some embodiments of this specification. As shown in Figure 4A, the NFC tag circuit 400 may include a second NFC chip 402, a second low-pass filter 404, a second matching circuit 406, a second current-limiting element 408, and an NFC coil 410. Similar to the radio frequency transmitting circuit 300, the second low-pass filter 404 may include an inductor and a capacitor, utilizing its characteristic of allowing only signals below the cutoff frequency to pass through while blocking signals above the cutoff frequency to filter out high-order harmonics of the crystal oscillator, thereby improving the stability of signal transmission. The second current-limiting element 408 may include a series resistor, which can adjust the balance between the quality factor (also known as the Q value) of the NFC coil 410 and the bandwidth of the circuit.

[0047] The second matching circuit 406 can tune with the NFC coil 410 and send the matched signal to the second NFC chip 402. The second NFC chip 402 then modulates the matched signal into a carrier signal and sends it to the NFC coil 410. The NFC coil can sense the NFC detection signal sent by the terminal device and send the aforementioned carrier signal.

[0048] Figure 4B shows an equivalent circuit diagram of an NFC tag circuit according to some embodiments of this specification. As shown in Figure 4B, the second NFC chip 402 can be represented as chip IC2 for signal modulation and demodulation and data reception and transmission, and stores specific information therein, including but not limited to order information, payment information, etc. Similarly, chip IC2 may include multiple pins, such as pin Rx for receiving external data, a transient voltage suppressor Tvss to ground to prevent circuit damage due to transient overvoltages (such as lightning strikes, electrostatic discharge, etc.), and differential signal transmission pins Tx+ and Tx- for high-speed, interference-resistant data transmission.

[0049] As shown in Figure 3B, the second low-pass filter 404 can be composed of an inductor L0 and a capacitor C0 to filter out high-order harmonics of the crystal oscillator. Capacitors C1 and C2 can form a second matching circuit 406 to adjust the impedance and resonant frequency parameters. Resistor R1 can serve as a second current-limiting element 408 to adjust the Q value of coil ANT2, i.e., the NFC coil 410, and the bandwidth of the circuit. This circuit operates based on the electromagnetic induction current of coil ANT2 when the terminal device is near it, without requiring an external power supply.

[0050] Figure 5 illustrates a flowchart of an NFC passive tag identification method according to some embodiments of this specification. It should be understood that method 500 may also include additional actions not shown and / or the actions shown may be omitted, and the scope of this disclosure is not limited in this respect.

[0051] As shown in Figure 5, in block 510, method 500 may include: collecting and storing ambient energy. Ambient energy may include, but is not limited to, ubiquitous, stable, and continuous wireless radio frequency energy, thermal energy, light energy, etc., and the acquisition method may include a corresponding energy harvesting circuit. Then, capacitors or lithium-ion batteries, etc., can be used to store and manage the electrical energy converted from ambient energy.

[0052] In block 520, method 500 may include: sending an excitation signal, based on ambient energy, to cause the terminal device to exit the low-power card detection (LPCD) mode. In some embodiments, the NFC chip may periodically transmit a carrier signal of a radio frequency field. When the terminal device in low-power card detection (LPCD) mode approaches the radio frequency field, it will switch from LPCD mode to normal card reading mode based on the radio frequency signal. In this way, NFC card reading efficiency can be improved in NFC passive tag scenarios with low cost and low power consumption.

[0053] In block 530, method 500 may include: sensing an NFC probe signal sent by the terminal device to communicate with the terminal device. Through the action of the aforementioned radio frequency field, it is ensured that the NFC tag circuit carrying specific information can interact with the terminal device in normal card reading mode, thereby achieving high-efficiency communication.

[0054] Furthermore, embodiments of this specification also provide NFC devices corresponding to the NFC passive tag identification system. The NFC device may include any of the NFC passive tag identification systems provided in the above embodiments.

[0055] Specifically, the NFC device may include an NFC passive tag identification system, which may include an energy harvesting circuit 102, an radio frequency transmission circuit 104, and an NFC tag circuit 106. The energy harvesting circuit 102 can collect and store ambient energy; the radio frequency transmission circuit 104, connected to the energy harvesting circuit 102 and powered by ambient energy, can be used to transmit an excitation signal to cause the terminal device to exit the low-power card detection (LPCD) mode; and the NFC tag circuit 106 can be used to sense the NFC detection signal transmitted by the terminal device to communicate with the terminal device.

[0056] In some embodiments, the energy harvesting circuit 102 may include at least one of the following: a radio frequency energy harvesting circuit; a thermal energy harvesting circuit; and a photovoltaic energy harvesting circuit.

[0057] In some embodiments, the system may further include a boost regulator circuit connected to the energy harvesting circuit 102 for increasing the output voltage of the energy harvesting circuit 102; and an oscillation circuit connected to the boost regulator circuit and the radio frequency transmission circuit 104 for generating periodic voltage signals and sending them to the radio frequency transmission circuit 104.

[0058] In some embodiments, the radio frequency transmitting circuit 104 may include a first NFC chip connected to and powered by an energy harvesting circuit for transmitting an excitation signal; an excitation coil connected to the first NFC chip for receiving and transmitting the excitation signal from the first NFC chip; and a first matching circuit connected to the first NFC chip and the excitation coil for adjusting impedance parameters and the resonant frequency parameters of the excitation coil.

[0059] In some embodiments, the radio frequency transmitting circuit 104 may further include a first filtering circuit connected to the first NFC chip for filtering out interference signals in the radio frequency transmitting circuit; and a first current limiting element connected to the excitation coil for adjusting the quality factor of the excitation coil and the bandwidth of the radio frequency transmitting circuit.

[0060] In some embodiments, the first filtering circuit may include a first low-pass filter, and the interference signal may include the higher harmonics of the crystal oscillator.

[0061] In some embodiments, the energy harvesting circuit 102, the radio frequency transmission circuit 104, and the NFC tag circuit 106 may be located in the same plane, and the energy harvesting circuit 102, the first NFC chip, and the NFC tag circuit 106 are all located inside the excitation coil.

[0062] In some embodiments, the NFC tag circuit 106 may include an NFC coil for sensing an NFC detection signal sent by a terminal device and generating an induced current; a second NFC chip connected to the NFC coil and powered by the induced current for sending a carrier signal carrying target data to the NFC coil to communicate with the terminal device; and a first matching circuit connected to the second NFC chip and the NFC coil for adjusting impedance parameters and the resonant frequency parameters of the NFC coil.

[0063] In some embodiments, the NFC tag circuit 106 may further include a second filtering circuit connected to the second NFC chip for filtering out interference signals in the NFC tag circuit; and a second current limiting element connected to the NFC coil for adjusting the quality factor of the NFC coil and the bandwidth of the NFC tag circuit.

[0064] In some embodiments, the second filtering circuit may include a second low-pass filter, and the interference signal includes the higher harmonics of the crystal oscillator.

[0065] In addition, the casing of NFC devices can be made of various non-metallic objects, including but not limited to PVC, acrylic, wood, etc., to avoid signal interference.

[0066] In the embodiments described in this specification, the NFC device operates in passive mode, and the terminal device communicating with the NFC device operates in active mode.

[0067] In the embodiments described in this specification, the NFC device operating in passive mode can not only passively complete communication, but also actively encourage the terminal device to communicate in normal working mode.

[0068] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0069] Various embodiments of this specification have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

[0070] The above are merely optional embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An NFC passive tag identification system, comprising: Energy harvesting circuits are used to collect and store environmental energy. The radio frequency transmitting circuit, connected to the energy harvesting circuit and powered by the ambient energy, is used to transmit an excitation signal to cause the terminal device to exit the low-power card detection LPCD mode. as well as An NFC tag circuit is used to sense the NFC detection signal sent by the terminal device in order to communicate with the terminal device.

2. The system of claim 1, wherein the energy harvesting circuit comprises at least one of the following: Radio frequency energy harvesting circuit; Heat harvesting circuit; and Photovoltaic energy harvesting circuit.

3. The system according to claim 1, wherein the system further comprises: A boost regulator circuit, connected to the energy harvesting circuit, is used to increase the output voltage of the energy harvesting circuit; as well as An oscillation circuit, connected to the boost regulator circuit and the radio frequency transmitting circuit, is used to generate periodic voltage signals and send them to the radio frequency transmitting circuit.

4. The system according to claim 1, wherein the radio frequency transmitting circuit comprises: The first NFC chip is connected to the energy harvesting circuit and powered by the energy harvesting circuit, and is used to send the excitation signal; An excitation coil, connected to the first NFC chip, is used to receive and transmit the excitation signal from the first NFC chip. as well as A first matching circuit, connected to the first NFC chip and the excitation coil, is used to adjust the impedance parameters and the resonant frequency parameters of the excitation coil.

5. The system according to claim 4, wherein the radio frequency transmitting circuit further comprises: A first filtering circuit, connected to the first NFC chip, is used to filter out interference signals in the radio frequency transmission circuit, wherein the first filtering circuit includes a first low-pass filter, and the interference signals include high-order harmonics of the crystal oscillator. as well as A first current-limiting element, connected to the excitation coil, is used to adjust the quality factor of the excitation coil and the bandwidth of the radio frequency transmission circuit.

6. The system according to claim 4, wherein the energy harvesting circuit, the radio frequency transmitting circuit and the NFC tag circuit are located in the same plane, and the energy harvesting circuit, the first NFC chip and the NFC tag circuit are all located inside the excitation coil.

7. The system of claim 1, wherein the NFC tag circuit comprises: An NFC coil is used to sense the NFC detection signal sent by the terminal device and generate an induced current. The second NFC chip is connected to the NFC coil and powered by the induced current. It is used to send a carrier signal carrying target data to the NFC coil to communicate with the terminal device. as well as A first matching circuit, connected to the second NFC chip and the NFC coil, is used to adjust the impedance parameters and the resonant frequency parameters of the NFC coil.

8. The system of claim 7, wherein the NFC tag circuit further comprises: A second filtering circuit, connected to the second NFC chip, is used to filter out interference signals in the NFC tag circuit, wherein the second filtering circuit includes a second low-pass filter, and the interference signals include high-order harmonics of the crystal oscillator. as well as A second current-limiting element, connected to the NFC coil, is used to adjust the quality factor of the NFC coil and the bandwidth of the NFC tag circuit.

9. An NFC passive tag identification method, comprising: Collect and store environmental energy; Based on the ambient energy, an excitation signal is sent to cause the terminal device to exit the low-power card detection LPCD mode; as well as The device senses the NFC detection signal sent by the terminal device to communicate with the terminal device.

10. An NFC device, wherein the NFC device operates in passive mode and a terminal device communicating with the NFC device operates in active mode, the NFC device comprising an NFC passive tag identification system as described in any one of claims 1-8.

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