A radio frequency identification tag

Abstract

This application provides a radio frequency identification (RFID) tag, which may include a coil, a first modulator connected to both ends of the coil, a second modulator connected to both ends of the coil, and a demodulator connected to both ends of the coil. The coil is used to receive a carrier wave. The demodulator is used to determine first data corresponding to the received carrier wave. The first modulator is used to transmit second data corresponding to the first data by adjusting the peak voltage across the coil when the tag is in a first operating mode. The second modulator is used to transmit the second data by adjusting the capacitance value across the coil when the first operating mode switches to a second operating mode, so that the tag's resonant frequency is consistent with that of a corresponding reader. In this embodiment of the invention, multiple modes, multiple protocols, and multiple frequency points of RFID functionality are supported with high performance under low power consumption and passive operation.

Description

Technical Field

[0001] The present application relates to the field of tags, and in particular to a radio frequency identification tag. Background Art

[0002] At present, automatic identification technology is widely popularized, especially radio frequency identification technology, which is an information technology with great development potential that people pay close attention to. This technology mainly uses wireless radio frequency to carry out non-contact two-way data communication, and uses wireless radio frequency to read and write recording media (such as electronic tags or radio frequency cards), so as to achieve the purpose of identification and data exchange.

[0003] Among them, the types of RF signal coupling between the reader and the electronic tag include inductive coupling and electromagnetic backscatter coupling. In the existing solutions, inductive coupling still has some common problems; for example, RFID tags cannot perfectly balance low power consumption while supporting multi-mode, multi-protocol, and multi-frequency data interaction functions. Summary of the invention

[0004] The present application provides a radio frequency identification tag that supports radio frequency identification of multiple modes, multiple protocols, and multiple frequencies with high performance in a low-power passive state.

[0005] In a first aspect, an embodiment of the present invention provides a radio frequency identification tag, which may include:

[0006] A coil, a first modulator connected to both ends of the coil, a second modulator connected to both ends of the coil, and a demodulator connected to both ends of the coil;

[0007] The coil is used to receive a carrier wave;

[0008] The demodulator is used to determine the first data corresponding to the carrier when the carrier is received;

[0009] The first modulator is used to send second data corresponding to the first data by adjusting the peak value of the voltage across the coil when the tag is in the first working mode;

[0010] The second modulator is used to adjust the capacitance value at both ends of the coil when the first working mode is switched to the second working mode, so that the resonant frequency point of the tag is consistent with that of the corresponding reader, so as to send the second data.

[0011] In an embodiment of the present invention, the demodulator demodulates the received carrier to obtain the first data; after necessary processing of the first data, the second data is fed back to the reader. When the tag is in the first working mode (such as the half-duplex mode HDX), the data is fed back by adjusting the voltage peak value at both ends of the coil. When the tag is in the second working mode (such as the full-duplex mode FDX), the data is fed back by adjusting the capacitance value at both ends of the coil. The content of the data fed back in different modes is not limited. Different from the prior art, the problem of frequency switching after the first working mode is switched to the second working mode is realized by adjusting the capacitance value of the coil by the second modulator. For example, when the tag switches to the HDX working mode, the frequency switching problem of the mode change is solved by the long-term operation of the second modulator. Furthermore, the demodulation circuit is adjusted to adapt to the carrier reception and demodulation of the two working modes.

[0012] In one possible implementation, two capacitors may be set in the aforementioned second operating mode; the first capacitor may be a tuning capacitor for resonating with the reader; the second capacitor may be a modulation capacitor used when sending data, and frequency modulation is achieved by adjusting the capacitance to send the second data.

[0013] In a possible implementation, the demodulator includes a switch tube, and the demodulator increases detection sensitivity and reduces delay time through the switch tube, so as to adapt to the first working mode and the second working mode. The demodulator adopts an envelope detection method, and two NMOS tubes are added to its basic circuit as switch tubes, so that the detection sensitivity is increased and the delay time is reduced, so that it can work at a higher baud rate.

[0014] In a possible implementation, the tag further includes a trimming circuit connected to both ends of the coil, the trimming circuit including one or more capacitors; the trimming circuit is used to: change the capacitance value of both ends of the coil by connecting the one or more capacitors to change the resonant frequency point of the tag. The purpose is to achieve the consistency of the resonant frequency of the tag with the resonant frequency of the reader.

[0015] In a possible implementation, the first modulator includes a load; the first modulator is specifically used to: control the load to be connected to the coil to reduce the peak voltage across the coil; or control the load not to be connected to the coil to restore the peak voltage across the coil.

[0016] In one possible implementation, the tag also includes a gap clock recovery circuit and a gap demodulator connected to the gap clock recovery circuit; the gap clock recovery circuit is connected to both ends of the coil; the gap demodulator is connected to both ends of the coil; the gap demodulator includes a capacitor (a capacitor is a filter with a variable time constant; optionally, it can also be a resistor, etc.); the gap clock recovery circuit is used to generate a first clock signal; the gap demodulator is used to: when the carrier is not received and the first clock signal exists, determine the corresponding time constant based on a preset reference current and the capacitance value of the capacitor to control the voltage of the capacitor to be within a threshold range.

[0017] In a possible implementation, the tag further includes a peak detection circuit connected to one end of the coil; the peak detection circuit is used to detect whether the coil has reached the preset voltage peak. The tag further includes a resonant circuit, a resonant switch and a counter; the counter is used to count to determine whether a preset time has been reached; when the preset time has been reached and the coil has reached the preset voltage peak, the resonant switch is turned on to charge the resonant circuit if the tag does not receive the carrier.

[0018] In a possible implementation, the tag further includes a rectifier bridge; the rectifier bridge is connected to two ends of the coil; the rectifier bridge is used to: generate a DC signal according to the carrier; the DC signal is used to supply power to the tag.

[0019] In a second aspect, an embodiment of the present invention provides a radio frequency identification tag (or radio frequency identification electronic tag, electronic tag), which may include:

[0020] Coil, gap clock recovery circuit and gap demodulator; the gap clock recovery circuit is connected to the gap demodulator; the gap clock recovery circuit

[0021] connected to both ends of the coil; the gap demodulator is connected to both ends of the coil; the gap demodulator includes a filter with a variable time constant; optionally, the filter can be a resistor or a capacitor. The coil is used to receive a carrier; when the electronic tag is in gap mode, the gap clock recovery circuit is used to: generate a first clock signal; the first clock signal is used to input the gap demodulator; when the carrier is not received and the first clock signal exists, the gap demodulator is used to: determine the corresponding time constant according to the preset reference current and the capacitance value of the capacitor, so as to control the voltage of the capacitor to be within the threshold range.

[0022] In an embodiment of the present invention, when the electronic tag is in the identification area of ​​the corresponding reader, the electronic tag receives the signal sent by the reader through the coil. In the case where there is a gap in the actual sent signal, or the signal sent by the reader is abnormal, a first clock signal is generated by a gap clock recovery circuit, and the clock signal is input to a gap demodulator connected to the gap clock recovery circuit; at this time, if the carrier (i.e., the signal sent by the reader) is still not received and the first clock signal exists, the gap demodulator is used to determine the time constant according to preset parameters (such as reference current, capacitor value), and control the capacitor voltage to be within a normal range. Compared with the prior art, the embodiment of the present invention can cooperate with the gap clock recovery circuit and the gap demodulator to enable the electronic tag to operate stably and normally in the case of a gap in the signal sent by the reader, so as to cope with the gap or reader abnormality and maintain the stability of the radio frequency identification tag; the gap mode is also provided on the basis of the normal working mode to cope with emergencies and support multiple working modes, protocols, and frequencies. Among them, the gap mode can be a signal processing mode for the electronic tag to cope with the gap in the carrier sent by the reader.

[0023] Optionally, when the electronic tag (such as the antenna part of the electronic tag) does not receive the carrier and the first clock signal does not exist, the gap demodulator cannot operate normally without other circuit components. For example, when the gap clock recovery circuit operates normally and the electronic tag receives the carrier, the gap clock recovery circuit can generate a clock signal from the carrier to provide the gap demodulator with a demodulation signal input.

[0024] In one possible implementation, when the carrier is received and the voltage is not within the threshold range, the gap demodulator is also used to demodulate the first data corresponding to the carrier. For example, when the voltage reaches the upper limit of a certain threshold range, the output of the first clock signal (such as CLK1) is flipped, so that the data sent by the reader (which may correspond to the first data) can be demodulated. Specifically, when the reader modulates, the clock signal does not flip for a period of time. At this time, the capacitor voltage reaches a certain threshold after a certain period of time, causing the output to flip, so that the tag can demodulate the data sent by the reader. For a specific process description, please refer to Figure 4 Contents shown and related descriptions.

[0025] In one possible implementation, the electronic tag further includes a rectifier bridge; the rectifier bridge is connected to both ends of the coil; the rectifier bridge is used to: generate a DC signal according to the carrier; the DC signal is used to power the electronic tag. The carrier is a radio frequency energy, which can be a specific AC signal in form; the AC signal is received by an antenna (corresponding to the aforementioned coil). Optionally, the transponder chip included in the radio frequency identification tag can be a passive chip; and the operating current of the submodule inside the chip needs to meet the low power consumption requirement. For example, the operating current of the entire analog circuit can be lower than a certain value, such as 3ua, 4ua, 5ua or 6ua.

[0026] In one possible implementation, the electronic tag also includes a limiter connected to both ends of the coil; the limiter is used to control the energy coupled to the electronic tag within a preset energy range. In a radio frequency identification system, the distance between the reader and the transponder is generally different in different devices and different application scenarios. The energy obtained by the transponder chip decreases as the distance between it and the reader increases. In order to prevent excessive energy from being obtained due to a close distance, a protection circuit or a discharge path can be added to the tag or chip in combination with specific devices and application scenarios. For example, the limiter can include a discharge path (discharge resistor circuit or discharge loop) to control the energy obtained by coupling to prevent damage to the chip in the tag, thereby protecting the chip.

[0027] In a possible implementation, the electronic tag further includes a trimming circuit connected to both ends of the coil; the trimming circuit is used to adjust the resonant frequency point of the electronic tag by changing the capacitance value at both ends of the coil to maintain the performance of the electronic tag.

[0028] In a possible implementation, the electronic tag further includes a clock recovery circuit connected to both ends of the coil; the clock recovery circuit is used to generate a second clock signal by comparing the voltages at both ends of the coil; the second clock signal is a clock signal that varies within a preset clock signal range. For example, in order to prevent glitches in the generated second clock signal, which causes the digital circuit to run away, the clock recovery circuit may include a comparator with hysteresis to compare the voltages at both ends of the inductor. The second clock signal generated after the voltage comparison is a basically stable clock signal.

[0029] In a possible implementation, the electronic tag further includes a demodulator connected to both ends of the coil; when the carrier is received and the electronic tag is not in the gap mode, the demodulator is used to determine the second data corresponding to the carrier by demodulating the waveform of the carrier. Specifically, the demodulator can obtain the second data contained in the carrier by determining the carrier waveform. The specific content of the second data may be the same as or different from the aforementioned first data, which is not limited in this embodiment of the present invention. The gap mode can be a signal processing mode in which the electronic tag responds to the presence of gaps in the carrier sent by the reader.

[0030] In a possible implementation, the electronic tag further includes a first modulator connected to both ends of the coil and a second modulator connected to both ends of the coil; the first modulator is used to control the amplitude of the inductance (which may be the aforementioned voltage peak value) to affect the third data fed back by the electronic tag; the second modulator is used to change the resonant frequency through the capacitance value of the inductance to affect the third data. The first modulator may be an amplitude shift keying modulator, and the second modulator may be a frequency shift keying modulator.

[0031] In a possible implementation, the electronic tag further includes a peak detection circuit connected to one end of the coil; the peak detection circuit includes a switch tube;

[0032] The peak detection circuit is used to detect whether the coil reaches a peak value;

[0033] When the peak value is reached, the peak detection circuit is further used to: turn on the switch tube to charge the LC parallel resonant circuit in the electronic tag to reduce power consumption. For example, turning on the switch tube in the peak detection circuit, charging at this time can reduce the loss of charge neutralization and achieve the effect of minimum power consumption.

[0034] Optionally, when the electronic tag is not in gap mode, the electronic tag can receive the carrier sent by the reader through the antenna and obtain data corresponding to the carrier; after processing the obtained data, the electronic tag modulates and sends the data in a corresponding form to the reader, thereby forming data interaction with the reader.

[0035] In a third aspect, an embodiment of the present invention provides a radio frequency identification device, which may include: a transponder chip, a coil connected to the transponder chip, and a plurality of capacitors and inductors. The transponder chip may include a gap clock recovery circuit and a gap demodulator; the gap clock recovery circuit is connected to the gap demodulator; the gap clock recovery circuit is connected to both ends of the coil; the gap demodulator is connected to both ends of the coil; the gap demodulator may include a capacitor;

[0036] The coil is used to receive a carrier wave;

[0037] When the electronic tag is in the gap mode, the gap clock recovery circuit is used to: generate a first clock signal; the first clock signal is used to input the gap demodulator;

[0038] When the carrier is not received and the first clock signal exists, the gap demodulator is used to: determine a corresponding time constant according to a preset reference current and a capacitance value of the capacitor to control the voltage of the capacitor to be within a threshold range.

[0039] In a possible implementation, when the carrier is received and the voltage is not within the threshold range, the gap demodulator is further used to demodulate the first data corresponding to the carrier. For example, when the voltage reaches an upper limit of a certain threshold range, the output of the first clock signal (such as CLK1) is flipped, so that the data sent by the reader (which may correspond to the first data) can be demodulated.

[0040] In one possible implementation, the electronic tag also includes a rectifier bridge; the rectifier bridge is connected to both ends of the coil; the rectifier bridge is used to: generate a DC signal according to the carrier; the DC signal is used to supply power to the aforementioned chip. Among them, the carrier is a radio frequency energy, which can be a specific AC signal in form; the AC signal is received by the antenna (corresponding to the aforementioned coil). Optionally, the transponder chip included in the radio frequency identification tag can be a passive chip; and the operating current of the sub-module inside the chip needs to meet the low power consumption requirement. For example, the operating current of the entire analog part circuit can be lower than a certain value, such as 3ua, 4ua, 5ua or 6ua.

[0041] In one possible implementation, the electronic tag also includes a limiter connected to both ends of the coil; the limiter is used to control the energy coupled to the electronic tag within a preset energy range. In a radio frequency identification system, the distance between the reader and the transponder is generally different in different devices and different application scenarios. The energy obtained by the transponder chip decreases as the distance between it and the reader increases. In order to prevent excessive energy from being obtained due to a close distance, a protection circuit or a discharge path can be added to the tag or chip in combination with specific devices and application scenarios. For example, the limiter can include a discharge path (discharge resistor circuit or discharge loop) to control the energy obtained by coupling to prevent damage to the chip in the tag, thereby protecting the chip.

[0042] In a possible implementation, the electronic tag further includes a trimming circuit connected to both ends of the coil; the trimming circuit is used to adjust the resonant frequency point of the aforementioned chip by changing the capacitance value at both ends of the coil to maintain the performance of the chip and avoid chip performance degradation. When the inductance and capacitance of the chip periphery are mismatched, the resonant frequency point of the aforementioned chip will be inconsistent with the resonant frequency point of the reader, causing the performance of the chip to degrade; in order to improve the aforementioned situation, a trimming circuit can be added inside the aforementioned chip to change the capacitance value at both ends of the inductance to change the resonant frequency point of the chip, so that the chip performance will not be degraded due to the mismatch of the peripheral inductance and capacitance.

[0043] In one possible implementation, the electronic tag also includes a clock recovery circuit connected to both ends of the coil; the clock recovery circuit is used to generate a second clock signal by comparing the voltages at both ends of the coil; the second clock signal is a clock signal that varies within a preset clock signal range. Both the second clock signal and the first clock signal can be recovered from the magnetic field received by the tag antenna, and the signal frequencies of the two are consistent, but there is a difference between the rising edge and the falling edge. For example, in order to prevent the generated second clock signal from having glitches, causing the digital circuit to run away, the clock recovery circuit may include a comparator with hysteresis to compare the voltages at both ends of the inductor. Among them, the second clock signal generated after voltage comparison is a basically stable clock signal.

[0044] In a possible implementation, the electronic tag further includes a demodulator connected to both ends of the coil; when the carrier is received and the electronic tag is not in the gap mode, the demodulator is used to determine the second data corresponding to the carrier by demodulating the waveform of the carrier. Specifically, the demodulator can obtain the second data contained in the carrier by determining the carrier waveform. The specific content of the second data and the aforementioned first data may be the same or different, and this is not limited in the embodiment of the present invention.

[0045] In a possible implementation, the electronic tag further includes a first modulator connected to both ends of the coil and a second modulator connected to both ends of the coil; the first modulator is used to control the amplitude of the inductor (which may be the aforementioned voltage peak value) to affect the third data fed back by the electronic tag; the second modulator is used to change the resonant frequency by the capacitance value of the inductor to affect the third data. Among them, the first modulator may be an amplitude shift keying modulator ASK, and the second modulator may be a frequency shift keying modulator FSK. For example, when working in the amplitude shift keying HDX mode, the transponder will send data (which may be the aforementioned third data) to the reader after calculating and processing the data demodulated by the demodulator circuit. For another example, when working in the frequency shift keying FDX mode, the resonant frequency is changed by changing the capacitance value between the two ends of the inductor, and the reader demodulates the data sent by the transponder (which may be the aforementioned third data) through the change of the resonant frequency. The third data is affected by different factors in different modes; in this embodiment, the data fed back by the transponder to the reader can be the third data.

[0046] In a possible implementation, the electronic tag further includes a peak detection circuit connected to one end of the coil; the peak detection circuit includes a switch tube;

[0047] The peak detection circuit is used to detect whether the coil reaches a peak value;

[0048] When the peak value is reached, the peak detection circuit is further used to: turn on the switch tube to charge the LC parallel resonant circuit in the electronic tag to reduce power consumption. For example, turning on the switch tube in the peak detection circuit, charging at this time can reduce the loss of charge neutralization and achieve the effect of minimum power consumption.

[0049] In a fourth aspect, an embodiment of the present invention provides another radio frequency identification device, including the functions of any module or circuit in the first aspect; the radio frequency identification device has the functions involved in the radio frequency identification tag, such as demodulation and modulation of signal lights.

[0050] In a fifth aspect, an embodiment of the present invention provides a radio frequency identification chip, which may include a rectifier bridge, a limiter, a trimming circuit, an FSK modulator, a load modulator (such as a modulator for ASK), a clock recovery circuit, a demodulator, a peak detection circuit (Peak detector), a resonant trigger (resonant trigger), a gap clock recovery circuit (GAP ClockRegenerator), a gap demodulator (GAP Demodulator), a power-on reset circuit (Power-on reset, POR), a low dropout linear regulator (Low dropout linear regulator, LDO), a current reference source (current reference), an electrically erasable programmable read-only memory (EEPROM), a digital module and a shift register (Shift register).

[0051] Among them, the peak detection circuit, the resonant trigger and the peripheral LC parallel resonant circuit constitute a transponder self-oscillator. For example, when working in FDX mode, since the reader has stopped sending the carrier at this time, the chip needs a low-power self-oscillation circuit to maintain the resonance of the inductor and capacitor. When the reader stops sending the carrier, the voltage across the inductor will drop. This is because the series resistance of the inductor between LC and the energy consumed by the inductor to send data. In order to maintain the LC resonance for a long time, it is necessary to continuously obtain energy from the VCC capacitor. Therefore, after a certain period of time, PG turns on the switch tube and VCC charges the LC circuit. In this self-oscillator, the time can also be calculated by a counter, and the peak detection circuit detects the peak value of a certain section of the coil. When both conditions are met, the PG turns on the switch tube to charge the LC circuit. Since this circuit does not require a driving circuit, it has the advantages of low power consumption and working at the resonant frequency point.

[0052] Optionally, the LDO can provide a low power supply voltage for the digital part in the chip. The specific connection relationship between each circuit and module can be referred to the description of the above aspects, which will not be repeated here.

[0053] In a sixth aspect, an embodiment of the present invention provides a radio frequency identification system, including a reader and a transponder; wherein the reader includes a reader chip, a microprocessor MCU and other necessary components such as capacitors and coils; the transponder includes a transponder chip and peripheral capacitors, coils and other necessary components. The reader sends a certain energy signal, and after receiving the energy signal, the transponder feeds back corresponding data according to the energy signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0055] Figure 1 This is a schematic diagram of an application scenario of a radio frequency identification tag provided by an embodiment of the present invention;

[0056] Figure 2 It is a structural diagram corresponding to a demodulation function in a GAP mode provided by an embodiment of the present invention;

[0057] Figure 3 It is a structural schematic diagram of a gap clock recovery circuit provided by an embodiment of the present invention;

[0058] Figure 4 is a schematic structural diagram of a gap demodulator provided by an embodiment of the present invention;

[0059] Figure 5 It is a schematic diagram of the module structure of a transponder chip provided by an embodiment of the present invention;

[0060] Figure 6 It is a structural schematic diagram of a demodulator provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of this application.

[0062] The terms "first", "second", "third" and "fourth" etc. in the specification and claims of the present application and the drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0063] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0064] First, some names involved in the embodiments of the present invention are explained.

[0065] (1) Resonant frequency refers to the resonant frequency that may occur in a circuit containing capacitors and inductors. If the capacitor and inductor are connected in parallel, the voltage of the capacitor gradually increases while the current gradually decreases; the current of the inductor gradually increases while the voltage of the inductor gradually decreases within a very small period of time.

[0066] (2) Demodulator: A device that uses digital signal processing technology to restore low-frequency digital signals modulated in high-frequency digital signals. Demodulators are widely used in the transmission and restoration of information such as broadcasting (audio signals) and television (video signals). Demodulators are generally used in pairs with modulators. The modulator is used to process digital signals into high-frequency signals for transmission, while the demodulator restores digital signals to their original signals.

[0067] (3) Envelope-demodulation is a vibration signal processing method based on filter detection, especially for early faults and fault signals with low signal-to-noise ratio. By connecting the peak points of a high-frequency signal over a period of time, we can get an upper (positive) line and a lower (negative) line. These two lines are called envelopes. The envelope is a curve that reflects the amplitude change of the high-frequency signal. For high-frequency signals of equal amplitude, these two envelopes are parallel lines. When a high-frequency signal is amplitude modulated (i.e., amplitude modulated) by a low-frequency signal, the low-frequency signal becomes the envelope of the high-frequency signal.

[0068] (4) Shift Register is a sequential logic circuit that can be used to store or transfer data in binary form. It loads the input data and then moves or "shifts" it to its output on each clock cycle.

[0069] (5) Baud rate can be understood as how many code elements a device sends (or receives) in one second. It is a measure of the symbol transmission rate, indicating the number of symbols transmitted per unit time (symbol rate).

[0070] Next, one application scenario of the radio frequency electronic tag provided by the embodiment of the present invention is described. Figure 1, Figure 1 is a schematic diagram of an application scenario of a radio frequency identification tag provided by an embodiment of the present invention; Figure 1 As shown in the figure, the coupling type of inductive coupling is used for explanation. The application scenario may include a microprocessor MCU, a reader chip and a transponder chip. Specifically, the MCU is connected to the reader chip to exchange data with the reader chip, or to control the content of the data sent by the reader or to further process the data obtained by the reader. The reader chip sends a certain energy signal (i.e. Figure 1 The energy shown in the figure covers a certain area; the reader chip sends signals within its range at a certain frequency or data transmission frequency (i.e. Figure 1 The data shown); After the transponder chip is within the signal coverage of the reader, it can obtain specific energy, which not only provides power for some circuits in the chip, but also demodulates the received signal, modulates the signal that meets the requirements, and feeds back the re-modulated signal to the reader chip through the peripheral coil (i.e. Figure 1 Data shown'). Figure 1 The VCC and GND in FIG. 1 are exemplary notations for the capacitors connected to the transponder chip.

[0071] It should be noted that this application scenario is only an exemplary scenario description; the application scenarios involved in the embodiments of the present invention include but are not limited to the above application scenarios.

[0072] See also Figure 2 , Figure 2 is a schematic diagram of a structure corresponding to a demodulation function in a GAP mode provided by an embodiment of the present invention; Figure 2 As shown, it may include a gap clock recovery circuit and a gap demodulator; the gap clock recovery circuit is connected to the gap demodulator; the gap clock recovery circuit is connected to both ends of the coil; the gap demodulator is connected to both ends of the coil; the gap demodulator includes a capacitor;

[0073] The coil is used to receive a carrier wave;

[0074] When the electronic tag is in the gap mode, the gap clock recovery circuit is used to: generate a first clock signal; the first clock signal is used to input the gap demodulator;

[0075] When the carrier is not received and the first clock signal exists, the gap demodulator is used to: determine a corresponding time constant according to a preset reference current and a capacitance value of the capacitor to control the voltage of the capacitor to be within a threshold range.

[0076] in, Figure 2The LC circuit involved in and the LC circuits mentioned in the subsequent embodiments are common knowledge in the art and will not be described in detail here.

[0077] In an embodiment of the present invention, when the electronic tag is in the identification area of ​​the corresponding reader, the electronic tag receives the signal sent by the reader through the coil. In the case where there is a gap in the actual transmitted signal, or the signal sent by the reader is abnormal, a first clock signal is generated by a gap clock recovery circuit, and the clock signal is input to a gap demodulator connected to the gap clock recovery circuit; at this time, if the carrier (i.e., the signal sent by the reader) is still not received and the first clock signal exists, the gap demodulator is used to determine the time constant according to preset parameters (such as reference current, capacitor value) to control the capacitor voltage to be within a normal range. Compared with the prior art, the embodiment of the present invention can solve the corresponding gap or reader abnormality through the cooperation of the gap clock recovery circuit and the gap demodulator to maintain the stability of the radio frequency identification tag; a gap mode is also provided on the basis of the normal working mode to cope with emergencies, and multiple working modes, protocols, and frequencies are supported.

[0078] See also Figure 3 , Figure 3 is a schematic diagram of the structure of a gap clock recovery circuit provided by an embodiment of the present invention; Figure 3 As shown in the figure, when working in GAP mode, the GAP clock recovery circuit is used to generate a clock signal from the carrier, which is used as a clock for the digital part and as a demodulated signal input for the gap demodulator. This circuit adds a latch function so that when the READER is modulated, CLK1 (a clock signal) does not flip erroneously.

[0079] See also Figure 4 , Figure 4 is a schematic diagram of the structure of a gap demodulator provided by an embodiment of the present invention; Figure 4 As shown, when the reader READER is not modulated, CLK1 is the clock generated by the gap clock recovery circuit GAP Clock Regenerator, and CLK1 always exists. By setting a suitable reference current Iref and the capacitance value of the capacitor C0, and selecting a suitable time constant, the voltage of the capacitor C0 is always below the threshold of the specific circuit component; when the reader is modulated, CLK1 will not flip for a period of time. At this time, the voltage of the capacitor will be charged to above the threshold of the specific circuit component (such as a Schmitt trigger, or Smith) after a certain period of time, causing the output to flip, thereby demodulating the data sent by the reader.

[0080] In a possible implementation, when the carrier is received and the voltage is not within the threshold range, the gap demodulator is further used to demodulate the first data corresponding to the carrier. For example, when the voltage reaches an upper limit of a certain threshold range, the output of the first clock signal (such as CLK1) is flipped, so that the data sent by the reader (which may correspond to the first data) can be demodulated.

[0081] In one possible implementation, the electronic tag also includes a rectifier bridge; the rectifier bridge is connected to both ends of the coil; the rectifier bridge is used to: generate a DC signal according to the carrier; the DC signal is used to supply power to the aforementioned chip. Among them, the carrier is a radio frequency energy, which can be a specific AC signal in form; the AC signal is received by the antenna (corresponding to the aforementioned coil). Optionally, the transponder chip included in the radio frequency identification tag can be a passive chip; and the operating current of the sub-module inside the chip needs to meet the low power consumption requirement. For example, the operating current of the entire analog part circuit can be lower than a certain value, such as 3ua, 4ua, 5ua or 6ua.

[0082] In one possible implementation, the electronic tag also includes a limiter connected to both ends of the coil; the limiter is used to control the energy coupled to the electronic tag within a preset energy range. In a radio frequency identification system, the distance between the reader and the transponder is generally different in different devices and different application scenarios. The energy obtained by the transponder chip decreases as the distance between it and the reader increases. In order to prevent excessive energy from being obtained due to a close distance, a protection circuit or a discharge path can be added to the tag or chip in combination with specific devices and application scenarios. For example, the limiter can include a discharge path (discharge resistor circuit or discharge loop) to control the energy obtained by coupling to prevent damage to the chip in the tag, thereby protecting the chip.

[0083] In a possible implementation, the electronic tag further includes a trimming circuit connected to both ends of the coil; the trimming circuit is used to adjust the resonant frequency point of the aforementioned chip by changing the capacitance value at both ends of the coil to maintain the performance of the chip and avoid chip performance degradation. When the inductance and capacitance of the chip periphery are mismatched, the resonant frequency point of the aforementioned chip will be inconsistent with the resonant frequency point of the reader, causing the performance of the chip to degrade; in order to improve the aforementioned situation, a trimming circuit can be added inside the aforementioned chip to change the capacitance value at both ends of the inductance to change the resonant frequency point of the chip, so that the chip performance will not be degraded due to the mismatch of the peripheral inductance and capacitance.

[0084] In a possible implementation, the electronic tag further includes a clock recovery circuit connected to both ends of the coil; the clock recovery circuit is used to generate a second clock signal by comparing the voltages at both ends of the coil; the second clock signal is a clock signal that varies within a preset clock signal range. For example, in order to prevent glitches in the generated second clock signal, which causes the digital circuit to run away, the clock recovery circuit may include a comparator with hysteresis to compare the voltages at both ends of the inductor. The second clock signal generated after the voltage comparison is a basically stable clock signal.

[0085] In a possible implementation, the electronic tag further includes a demodulator connected to both ends of the coil; when the carrier is received and the electronic tag is not in the gap mode, the demodulator is used to determine the second data corresponding to the carrier by demodulating the waveform of the carrier. Specifically, the demodulator can obtain the second data contained in the carrier by determining the carrier waveform. The specific content of the second data and the aforementioned first data may be the same or different, and this is not limited in the embodiment of the present invention.

[0086] In a possible implementation, the electronic tag further includes a first modulator connected to both ends of the coil and a second modulator connected to both ends of the coil; the first modulator is used to control the amplitude of the inductor to affect the third data fed back by the electronic tag; the second modulator is used to change the resonant frequency by the capacitance value of the inductor to affect the third data. The first modulator may be an amplitude-shift keying (ASK) modulator, and the second modulator may be a frequency-shift keying (FSK) modulator.

[0087] In a possible implementation, the electronic tag further includes a peak detection circuit connected to one end of the coil; the peak detection circuit includes a switch tube; the peak detection circuit is used to detect whether the coil has reached a peak value; when the peak value is reached, the peak detection circuit is further used to: turn on the switch tube to charge the LC parallel resonant circuit in the electronic tag to reduce power consumption. For example, turning on the switch tube in the peak detection circuit, charging at this time can reduce the loss of charge neutralization and achieve the effect of minimum power consumption.

[0088] It should be noted that the internal architecture of the chip shown in the embodiment of the present invention is only an exemplary description; the content involved in this application includes but is not limited to the description of the above-mentioned module functions, types and connection relationships.

[0089] See also Figure 5 , Figure 5 is a schematic diagram of a module structure of a transponder chip provided by an embodiment of the present invention; Figure 5 As shown, it may include a rectifier bridge 1, a limiter 2, a trimming circuit 3, an FSK modulator 4, a load modulator (such as an ASK modulator) 5, a clock recovery circuit 6, a demodulator 7, a gap clock recovery circuit 10, a gap demodulator 11, a power-on reset circuit (Power-on reset, POR) 12, a low dropout linear regulator (LDO) 13, a current reference 14, an electrically erasable programmable read only memory (EEPROM) 15, a digital module / digital circuit 16 and a shift register 17; it can be understood that the peak detection circuit (Peak detector) 8, a resonant trigger (resonant trigger) 9 and a switch, a counter, etc. constitute the self-excited oscillator of the chip. When the chip is in FDX working mode, since the reader has stopped sending the carrier, the inductor-capacitor resonance can be maintained by a low-power self-oscillation circuit.

[0090] Among them, the rectifier bridge 1 is used to convert the AC signal received by the antenna (ie, the coil) into a DC signal VCC, which provides power to the chip. Since the chip generally works passively, the working current of the submodule inside the chip needs to be low power, and the working current of the entire analog circuit is less than 3uA. Optionally, the chip can be an active or semi-active electronic tag to adapt to different scenarios and specific needs.

[0091] Limiter 2 is used to prevent the chip from being damaged by coupling excessive energy and to protect the chip by providing a discharge path.

[0092] The trimming circuit 3 is used to change the capacitance value at both ends of the inductor to change the resonant frequency point of the chip when there is a mismatch between the peripheral inductor and the capacitor, so as to avoid chip performance degradation due to the mismatch between the peripheral inductor and the capacitor.

[0093] FSK modulator 4 is used to change the capacitance value between the two ends of the inductor to change the resonant frequency when the chip works in FDX mode; the reader demodulates the data sent by the transponder by changing the resonant frequency. For example, when FSK-DATA=1, the resonant frequency will decrease due to the increase of the capacitance between the two ends of the inductor; when FSK-DATA=0, the capacitance value returns to the original value, and the resonant frequency also returns to the original value.

[0094] Load modulator 5 is used when the chip works in HDX mode. At this time, the transponder will calculate and process the data demodulated by the demodulator, and then send the data to the reader; that is, the transponder sends data to the reader through the load modulator. For example, in HDX mode, when ASK-DATA=1, a load is connected to both ends of the inductor, which will cause the amplitude of the inductor to drop a lot; when ASK-DATA=0, the amplitude does not drop because there is no load between the inductors. Then, the reader can demodulate the data sent by the transponder through the change of the amplitude of the inductor.

[0095] The clock recovery circuit 6 is used to compare the voltages across the inductor through a comparator with hysteresis to generate a stable clock signal (corresponding to the aforementioned second clock signal).

[0096] The demodulator 7 is used to demodulate the waveform sent by the reader, obtain the data sent by the reader, and then send the data to the digital circuit (digital). Optionally, see Figure 6 , Figure 6 is a schematic diagram of the structure of a demodulator provided by an embodiment of the present invention; Figure 6 As shown, the demodulator circuit adopts the envelope detection method, on which two NMOS tubes can be added as switch tubes, so that the sensitivity of the detection is increased and the delay time is reduced, so that it can work at a higher baud rate. In the demodulator circuit, R1, R2, R3, and R4 can be set with appropriate resistance values; when the reader is not modulated, the two NMOS are turned on in turn, and VP is always higher than VN at this time; when the reader modulates and sends data, the amplitude (i.e., the voltage peak) at both ends of COIL1 / COIL2 (corresponding to the two end nodes of the coil) will decrease, resulting in the two NMOS not being turned on, and VP will drop below VN at this time, so that the data sent by the reader can be demodulated from the waveform at both ends of the inductor, realizing data transmission between the transponder and the reader.

[0097] The peak detection circuit 8 is used to detect the voltage peak of Coil2. At the peak, PG (referring to the signal output by the peak detection circuit; this signal can be used to drive the gate of a MOSFET) turns on the switch to charge the LC circuit. Charging at this time can reduce the loss of charge neutralization and achieve the effect of minimum power consumption.

[0098] The resonance trigger 9 can refer to the description of the self-excited resonator in the fourth aspect mentioned above, which will not be repeated here.

[0099] The digital module 16 is used to calculate and obtain corresponding data results according to one or more of the preset data, keys, modes, protocols and other information.

[0100] Among them, the functions of the power-on reset circuit 12, the low-voltage dropout linear regulator 13, the current reference source 14, the electrically erasable programmable read-only memory 15, the shift register 17 and other devices are the same or similar to those in general RFID tags and are not further described in detail.

[0101] It should be noted that the internal architecture of the chip shown in the embodiment of the present invention is only an exemplary description; the content involved in this application includes but is not limited to the description of the functions, types and connection relationships of the above modules. Figure 1-Figure 6 The functional architecture and corresponding embodiments shown are exemplary descriptions. The architecture of the multifunctional watch with a car smart key provided by the embodiment of the present invention includes but is not limited to the above-mentioned functional architectures.

[0102] The above describes the radio frequency tag architecture and modules provided by the embodiment of the present invention. The following lists the working states of some modules involved in the embodiment of the present invention in multiple modes.

[0103] Please refer to Table 1, which is a module working status table in a multi-mode according to an embodiment of the present invention; the numbers in Table 1 correspond to the above Figure 5 The module number in .

[0104]

[0105] As shown in Table 1, on indicates that the module is in operation, and off indicates that the module is not in operation (or in sleep mode). Among them, three specific modes are listed, including HDX, FDX, and GAP. The embodiments of the present invention are described using the above modes as examples, but the specific working modes are not limited to the above three modes. It can be seen that on the basis of the basic working mode, HDX, FDX, and GAP modes are also provided, so that the chip supports multiple modes to cope with various situations and meet diverse needs.

[0106] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A radio frequency identification tag, characterized in that: include: A coil, a first modulator connected to both ends of the coil, a second modulator connected to both ends of the coil, and a demodulator connected to both ends of the coil; The coil is used to receive a carrier wave; The demodulator is used to determine the first data corresponding to the carrier when the carrier is received; The first modulator is used to send second data corresponding to the first data by adjusting the peak value of the voltage across the coil when the tag is in the first working mode; The second modulator is used to adjust the capacitance value at both ends of the coil when the first working mode is switched to the second working mode, so that the resonant frequency point of the tag is consistent with that of the corresponding reader, so as to send the second data.

2. The label according to claim 1, characterized in that: The demodulator includes a switch tube; the demodulator is used to increase detection sensitivity and reduce delay time through the switch tube, so as to adapt to the first working mode and the second working mode.

3. The label according to claim 1, characterized in that: The tag further includes a trimming circuit connected to both ends of the coil, wherein the trimming circuit includes one or more capacitors; the trimming circuit is used to: The one or more capacitors are controlled to change the capacitance value at both ends of the coil to adjust the resonant frequency point of the tag.

4. The label according to claim 1, characterized in that: The first modulator includes a load; the first modulator is further configured to: Control the load to be connected to the coil to reduce the peak voltage across the coil; or, The load is controlled not to be connected to the coil, and the peak value of the voltage at both ends of the coil is restored.

5. The label according to claim 1, characterized in that: The tag further comprises a gap clock recovery circuit and a gap demodulator connected to the gap clock recovery circuit; the gap clock recovery circuit is connected to both ends of the coil; the gap demodulator is connected to both ends of the coil; the gap demodulator comprises a capacitor; The gap clock recovery circuit is used to generate a first clock signal; The gap demodulator is used to: when the carrier is not received and the first clock signal exists, determine the corresponding time constant according to the preset reference current and the capacitance value of the capacitor to control the voltage of the capacitor to be within a threshold range.

6. The label according to claim 5, characterized in that: When the carrier is received and the voltage is not within the threshold range, the gap demodulator is further configured to determine the first data.

7. The label according to claim 1, characterized in that: The tag also includes a limiter connected to both ends of the coil; the limiter is used to control the energy coupled by the tag to be within a preset energy range.

8. The label according to claim 1, characterized in that: The tag also includes a clock recovery circuit connected to both ends of the coil; The clock recovery circuit is used to generate a second clock signal by comparing the voltages at both ends of the coil; the second clock signal is a clock signal that varies within a preset clock signal range.

9. The label according to claim 1, characterized in that: The tag further comprises a peak detection circuit connected to one end of the coil; the peak detection circuit is used to detect whether the coil reaches the peak value of the voltage at both ends.

10. The label according to claim 9, characterized in that: The tag also includes a resonant circuit, a resonant switch and a counter; the counter is used to count to determine whether a preset time has been reached; In the case that the tag does not receive the carrier, when the preset time is reached and the voltage across the coil reaches the peak value of the voltage across the coil, the resonant switch is turned on to charge the resonant circuit.

Images