A High Reliability RFID Backscatter Modulation Circuit

Abstract

This article relates to a high-reliability RFID backscatter modulation circuit, including an RFID basic module, an antenna strength detection module, a reference voltage generation module, a comparator, and an adjustable impedance switch; the antenna strength detection module is used to output a first voltage value according to the antenna signal strength of the two antenna receiving ends in the RFID basic module; the reference voltage generation module is used to generate a stable second voltage value; the adjustable impedance switch includes a multi-way switch resistor connected in parallel between the two antenna receiving ends, the switch state of the switch resistor is controlled by the data signal sent by the RFID basic module, at least one of the multi-way switch resistors has a transmission switch, and the transmission switch is used to control the transmission of the data signal of the corresponding switch resistor; the comparator is used to control the switch state of the transmission switch according to the first voltage value and the second voltage value. This article can effectively ensure the reliability of data communication under the condition of strong interference signals.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit technology, and in particular to a high-reliability RFID backscatter modulation circuit. Background Art

[0002] In a passive RFID system, the communication method used by the electronic tag to send data back to the reader is backscatter modulation. The principle of this communication method is to generate data signals on the reader by controlling the impedance of the electronic tag antenna. It is essentially a method based on "impedance switching" (a closed switch indicates 1, and an open switch indicates 0). Several types of impedance switches actually used include varactor diodes, logic gates, high-speed switches, etc. The schematic diagram is shown below. Figure 1 shown.

[0003] The data signal to be sent is a signal with two levels, which is modulated by the digital part. The modulation result is connected to an "impedance switch", which changes the impedance of the antenna to modulate the carrier signal. This data modulation method is very different from the ordinary data communication method. In the entire data communication link, there is only one transmitter, but it completes two-way data communication. The electronic tag changes the matching degree by controlling the antenna switch according to the data to be sent. In this way, the data returned from the tag is modulated on the amplitude of the returned electromagnetic wave.

[0004] As various wireless communication and wireless charging products are currently being used in large quantities, the surrounding space is filled with interference signals of different frequencies and amplitudes. When the coil antenna is in a strong interference environment, it is possible that the strong interference signal is coupled into the coil, changing the waveform of the normal backscattered signal, causing the card reader to interpret it incorrectly. Especially when the data signal power is very high and the reverse debugging depth is small, if it is interfered by a strong signal at this time, the depth of reverse modulation will be further reduced. When the depth of the reverse modulation signal is reduced to a certain extent, it will cause communication failure. Summary of the invention

[0005] To solve the problems in the prior art, the embodiments of this document provide a high-reliability RFID backscatter modulation circuit, which can effectively ensure the reliability of data communication in the presence of strong interference signals.

[0006] The embodiment of this specification provides a high-reliability RFID backscatter modulation circuit, including: an RFID basic module, an antenna strength detection module, a reference voltage generation module, a comparator, and an adjustable impedance switch;

[0007] The antenna strength detection module is used to output a first voltage value according to the antenna signal strength of the two antenna receiving ends in the RFID basic module;

[0008] The reference voltage generating module is used to generate a stable second voltage value;

[0009] The adjustable impedance switch includes a multi-way switch resistor connected in parallel between the two antenna receiving ends, the switch state of the switch resistor is controlled by the data signal sent by the RFID basic module, at least one switch resistor in the multi-way switch resistor has a transmission switch, and the transmission switch is used to control the transmission of the data signal of the corresponding switch resistor;

[0010] The comparator is used to control the switching state of the transmission switch according to the first voltage value and the second voltage value.

[0011] Further, the comparator is used to control the transmission switch to be closed when the first voltage value is higher than the second voltage value, and vice versa, control the transmission switch to be opened.

[0012] Furthermore, the multi-way switch resistor is a two-way switch resistor, wherein only one of the switch resistors has the transmission switch.

[0013] Further, the transmission switch includes a first inverter, a second inverter, a first switch and a second switch;

[0014] A first end of the first inverter is connected to an output end of the comparator, a second end of the first inverter is connected to a first end of the second inverter, a second end of the second inverter is connected to a control end of the first switch, and the first switch is used to control the transmission of a data signal having a switch resistance of the transmission switch;

[0015] The second end of the first inverter is also connected to the control end of the second switch, and the second switch is used to disconnect the switch resistor having the transmission switch when the switch state is closed.

[0016] Furthermore, at least one switch resistor is composed of a plurality of resistors connected in series.

[0017] Further, the antenna strength detection module includes a PMOS transistor PM1, a PMOS transistor PM2, a PMOS transistor PM3, a resistor R1 and a capacitor C1;

[0018] The gate of PM1 is used to input a reference voltage of an antenna signal, the resistor R1 is connected in series between the drain of PM1 and the output end of the antenna strength detection module, and the C1 is connected in series between the output end of the antenna strength detection module and the ground;

[0019] The source of PM1 is connected to the gate and drain of PM2 and the gate and drain of PM3 respectively;

[0020] The source of PM2 is connected to one antenna receiving end, and the source of PM3 is connected to another antenna receiving end.

[0021] Furthermore, the output end of the antenna strength detection module is connected to the first input end of the comparator, and the output end of the reference voltage generation module is connected to the second input end of the comparator.

[0022] Further, the comparator includes an operational amplifier and a variable resistor divider;

[0023] The first input terminal of the operational amplifier is connected to the first input terminal of the comparator, and the output terminal of the operational amplifier is connected to the output terminal of the comparator;

[0024] The output terminal of the operational amplifier and the second input terminal of the comparator provide a variable second voltage value to the second input terminal of the operational amplifier through the variable resistor divider.

[0025] Furthermore, the variable resistor voltage divider includes a plurality of resistors, at least one resistor has a voltage divider switch connected in parallel at both ends, and the output end of the operational amplifier is connected to the control end of the voltage divider switch.

[0026] Further, the variable resistor divider includes resistors R4, R5 and R6;

[0027] The R4 is connected in series between the second input terminal of the comparator and the second input terminal of the operational amplifier;

[0028] The R5 and R6 are connected in series, and are connected in series between the second input terminal of the operational amplifier and the ground;

[0029] The two ends of R6 are connected in parallel with the voltage divider switch.

[0030] Through the RFID backscatter modulation circuit of the embodiment of the present specification, the antenna signal strength is used as the adjustment index of the impedance in the backscatter modulation process, which is direct and effective. A multi-way switch resistor is connected in parallel between the two antenna receiving ends, and at least one switch resistor has a transmission switch. The transmission switch is used to control the transmission of the data signal of the corresponding switch resistor. The switching state of the transmission switch is controlled according to the antenna signal strength. According to the switching state of the transmission switch, it is determined whether the switch resistor corresponding to the transmission switch can receive the data signal, that is, according to the state of the transmission switch, it is determined whether the switch resistor corresponding to the transmission switch works between the two antenna receiving ends, and the switch resistor without the transmission switch can receive the data signal. Its operation between the two antenna receiving ends is not controlled by the antenna signal strength, thereby realizing the adjustment of the size of the impedance connected between the two antenna receiving ends according to the antenna signal strength. It has the advantages of flexible design and convenient digital control, and improves the communication reliability of the passive RFID tag under the condition of strong wireless charging signal interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of this article or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of this article. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is a block diagram of the principle of RFID backscatter modulation in the prior art;

[0033] Figure 2 This is a schematic diagram of the structure of a high-reliability RFID backscatter modulation circuit in an embodiment of this specification;

[0034] Figure 3 Schematic diagram of a circuit of an adjustable impedance switch in an embodiment of this specification;

[0035] Figure 4 Schematic diagram of the circuit of the antenna strength detection module in the embodiment of this specification;

[0036] Figure 5 Schematic diagram of a circuit of a reference voltage generating module in an embodiment of this specification;

[0037] Figure 6 Schematic diagram of a comparator circuit in an embodiment of this specification.

[0038] [Description of Reference Numerals]

[0039] 1. RFID basic module;

[0040] 11. Matching network;

[0041] 12. Antenna voltage limiter;

[0042] 13. AFE other functional circuits;

[0043] 14. Digital circuits;

[0044] 2. Antenna strength detection module;

[0045] 3. Reference voltage generation module;

[0046] 4. Comparator;

[0047] 41. Variable resistor divider;

[0048] 5. Adjustable impedance switch;

[0049] 51. Switch resistance;

[0050] St, transmission switch;

[0051] V1, first voltage value;

[0052] VREF1, second voltage value;

[0053] VREF2, reference voltage;

[0054] VREF3, a variable second voltage value;

[0055] Z1, Z2, switch resistance;

[0056] S1, S2, switch;

[0057] INV1, first inverter;

[0058] INV2, second inverter;

[0059] St1, first switch;

[0060] St2, second switch;

[0061] S5, voltage divider switch;

[0062] PM1, PM2, PM3, PM4, PM5, PM6, PMOS tube;

[0063] NM1, NM2, NMOS tube;

[0064] R1, R2, R3, R4, R5, R6, resistors;

[0065] C1, capacitor;

[0066] PNP1, PNP2, PNP transistors;

[0067] OPA, operational amplifier. DETAILED DESCRIPTION

[0068] The following will be combined with the drawings in the embodiments of this article to clearly and completely describe the technical solutions in the embodiments of this article. Obviously, the described embodiments are only part of the embodiments of this article, not all of the embodiments. Based on the embodiments of this article, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this article.

[0069] In order to solve the problems existing in the prior art, the embodiments of this specification provide a high-reliability RFID backscatter modulation circuit, such as Figure 2 As shown, it includes an RFID basic module 1, an antenna strength detection module 2, a reference voltage generation module 3, a comparator 4 and an adjustable impedance switch 5;

[0070] The antenna strength detection module 2 is used to output a first voltage value V1 according to the antenna signal strength of the two antenna receiving ends in the RFID basic module 1;

[0071] The reference voltage generating module 3 is used to generate a stable second voltage value VREF1;

[0072] The adjustable impedance switch 5 includes a multi-way switch resistor 51 connected in parallel between the two antenna receiving ends, and the switch state of the switch resistor 51 is controlled by the data signal sent by the RFID basic module 1. At least one switch resistor 51 in the multi-way switch resistor has a transmission switch St, and the transmission switch St is used to control the transmission of the data signal of the corresponding switch resistor 51;

[0073] The comparator 4 is used to control the switching state of the transmission switch St according to the first voltage value V1 and the second voltage value VREF1.

[0074] Through the RFID backscatter modulation circuit of the embodiment of the present specification, the antenna signal strength is used as the adjustment index of the impedance in the backscatter modulation process, which is direct and effective. A multi-way switch resistor is connected in parallel between the two antenna receiving ends, and at least one switch resistor has a transmission switch. The transmission switch is used to control the transmission of the data signal of the corresponding switch resistor. The switching state of the transmission switch is controlled according to the antenna signal strength. According to the switching state of the transmission switch, it is determined whether the switch resistor corresponding to the transmission switch can receive the data signal, that is, according to the state of the transmission switch, it is determined whether the switch resistor corresponding to the transmission switch works between the two antenna receiving ends, and the switch resistor without the transmission switch can receive the data signal. Its operation between the two antenna receiving ends is not controlled by the antenna signal strength, thereby realizing the adjustment of the size of the impedance connected between the two antenna receiving ends according to the antenna signal strength. It has the advantages of flexible design and convenient digital control, and improves the communication reliability of the passive RFID tag under the condition of strong wireless charging signal interference.

[0075] In the embodiment of this specification, the RFID basic module 1 may include: Figure 2 The matching network 11, antenna voltage limiter 12, AFE other functional circuit 13 and digital circuit 14 are shown in the figure. The matching network 11 is integrated inside the chip, resonates with the coil antenna, receives and sends wireless data signals, the antenna voltage limiter 12 limits the antenna voltage to a preset value, the AFE (analog front end) other functional circuit 13 provides the functions of rectification and filtering, reset signal generation, clock recovery, and data recovery, and the digital circuit 14 mainly completes the analysis of antenna recovery data and the generation of transmission data.

[0076] It should be noted that Figure 2 The structure of the RFID basic module 1 shown in the figure is merely exemplary, and the embodiments of this specification do not limit the specific structure of the RFID basic module 1.

[0077] In the embodiment of the present specification, the number of the multi-way switch resistors 51 in the adjustable impedance switch 5 can be greater than or equal to 2, wherein at least one switch resistor has a transmission switch St, and the switch state of the transmission switch St is controlled by the output end of the comparator 4. When the transmission switch St is closed, the data signal sent by the RFID basic module 1 can be transmitted to the switch resistor 51 corresponding to the transmission switch St, so the switch in the switch resistor 51 can set the switch state according to the data signal, which can be understood as, at this time, the switch resistor 51 corresponding to the transmission switch St is connected between the two antenna receiving ends. When the transmission switch St is disconnected, the data signal sent by the RFID basic module 1 is no longer transmitted to the switch resistor 51 corresponding to the transmission switch St, so the switch in the switch resistor 51 is no longer set the switch state according to the data signal, which can be understood as, at this time, the switch resistor 51 corresponding to the transmission switch St is not connected between the two antenna receiving ends.

[0078] Therefore, the output end of the comparator 4 can control the number of switch resistors 51 connected between the two antenna receiving ends. Because the multiple switch resistors 51 are connected in parallel, the output end of the comparator 4 can adjust the impedance between the two antenna receiving ends.

[0079] Specifically, the output end of the antenna strength detection module 2 is connected to the first input end of the comparator 4, and the output end of the reference voltage generation module 3 is connected to the second input end of the comparator 4. The comparator 4 is used to control the transmission switch St to be closed when the first voltage value V1 is higher than the second voltage value VREF1, and vice versa, control the transmission switch St to be opened.

[0080] In actual implementation, when the first voltage value V1 is higher than the second voltage value VREF1, the output end of the comparator 4 can output a high-level control signal, and the high-level control signal controls the closing of the transmission switch St. Conversely, the output end of the comparator 4 outputs a low-level control signal, and the low-level control signal controls the opening of the transmission switch St.

[0081] The data signal output by the RFID basic module 1 is a signal with two levels, the low level can be represented as 0, and the high level can be represented as 1. The data signal is used to control the switch state of the switch resistor 51. For example, when the data signal is at a low level, the switch of the switch resistor 51 is opened, and when the data signal is at a high level, the switch of the switch resistor 51 is closed.

[0082] Exemplarily, if the antenna signal strength is strong, the first voltage value V1 is higher than the second voltage value VREF1, the comparator 4 outputs a high-level control signal, and the transmission switch St is closed. When the data signal is at a high level, the switch of the switch resistor 51 corresponding to the closed transmission switch St is closed, and the switch of the switch resistor 51 without the transmission switch is closed. At this time, the impedance of the antenna is determined by the resistance value of the switch resistor 51 corresponding to the closed transmission switch St and the resistance value of the switch resistor 51 without the transmission switch. Because the switch resistors 51 are in parallel, the impedance of the antenna is relatively small at this time.

[0083] If the antenna signal strength is weak, the first voltage value V1 is lower than the second voltage value VREF1, the comparator 4 outputs a low-level control signal, and the transmission switch St is disconnected. When the data signal is at a high level, the high-level data signal cannot control the switch state of the switch resistor 51 corresponding to the transmission switch St that is disconnected. At this time, the switch resistor 51 is disconnected, and the switch of the switch resistor 51 without the transmission switch is closed. At this time, the impedance of the antenna is determined by the resistance value of the switch resistor 51 without the transmission switch, and the impedance of the antenna is relatively large.

[0084] Preferably, if Figure 2 As shown, the multi-way switch resistor 51 is a two-way switch resistor, including Z1 and Z2, wherein only the switch resistor Z2 has the transmission switch St. The switches of the switch resistors Z1 and Z2 are S1 and S2 respectively, and the switches S1 and S2 are selected to be closed or opened according to the data signal sent by the RFID basic module, such as the switch closed represents a high level 1, and the switch opened represents a low level 0. The control end of the transmission switch St is connected to the control signal output by the comparator 4, and the two signal ends of the transmission switch St are respectively connected to the transmitting end of the data signal and the control end of S2, and the transmitting end of the data signal is also connected to the control end of the switch S1. The transmission switch St sets the switch state according to the control signal output by the comparator 4, thereby determining whether the switch S2 receives the data signal, and then selecting different antenna impedances. When the antenna signal strength is weak, the first voltage value V1 output by the antenna strength detection module 2 is lower than the second voltage value VREF1, the comparator 4 outputs a low-level control signal, the transmission switch St is disconnected, the switch S2 in the switch resistor Z2 does not receive the data signal, and only the switch S1 in the switch resistor Z1 receives the data signal, thereby achieving a higher antenna impedance. When the antenna signal strength is strong, the first voltage value V1 output by the antenna strength detection module 2 is higher than the second voltage value VREF1, the comparator 4 outputs a high-level control signal, the transmission switch St is closed, and the switch S2 in the switch resistor Z2 and the switch S1 in the switch resistor Z1 both receive the data signal, thereby achieving a lower antenna impedance. It should be noted that since the antenna signal strength will be affected by the surrounding interference signal, the antenna voltage is very unstable. If the transmission switch St is connected in series between the switch resistor 51 and the antenna, if the transmission switch St uses an NMOS tube, its control terminal voltage needs to be greater than the source-drain voltage (i.e., the antenna voltage), and if the transmission switch St uses a PMOS tube, its control terminal voltage needs to be less than the source-drain voltage, and the antenna voltage is very unstable, so it may cause the transmission switch St to be unable to be completely closed. If a complex shutdown circuit is introduced, the circuit complexity will be greatly increased. Therefore, in the embodiment of this specification, the transmission switch St is connected in series between the sending end of the data signal and the control end of the switch of the switch resistor 51, rather than connecting the transmission switch St in series between the switch resistor 51 and the antenna, thereby improving reliability and reducing structural complexity.

[0085] According to one embodiment of this specification, Figure 3 As shown, the transmission switch St includes a first inverter INV1, a second inverter INV2, a first switch St1 and a second switch St2;

[0086] A first end of the first inverter INV1 is connected to the output end of the comparator 4, a second end of the first inverter INV1 is connected to a first end of the second inverter INV2, a second end of the second inverter INV2 is connected to a control end of the first switch St1, and the first switch St1 is used to control the transmission of a data signal having a switch resistance of the transmission switch;

[0087] The second end of the first inverter INV1 is also connected to the control end of the second switch St2. The second switch St2 is used to disconnect the switch resistor having the transmission switch when the switch state is closed.

[0088] like Figure 3 As shown, the switch resistor Z2 has a transmission switch St. When the comparator 4 outputs a low-level control signal, the first switch St1 is disconnected, that is, the switch S2 of the switch resistor Z2 does not receive a data signal. In order to avoid the control end of the switch S2 being suspended at this time, the embodiment of this specification adopts a first inverter INV1 to invert the low-level control signal to obtain a high-level signal, and control the second switch St2 to be closed, so that the control end of the switch S2 is grounded, thereby pulling down the control signal of the switch S2.

[0089] Furthermore, at least one switch resistor is composed of a plurality of resistors connected in series, such as Figure 3 As shown, the two groups of parallel switch resistors Z1 and Z2 have the same structure, and each group of switch resistors includes a switch and two resistors.

[0090] According to one embodiment of this specification, Figure 4 As shown, the antenna strength detection module includes a PMOS tube PM1, a PMOS tube PM2, a PMOS tube PM3, a resistor R1 and a capacitor C1;

[0091] The gate of PM1 is used to input the reference voltage VREF2 of the antenna signal, the resistor R1 is connected in series between the drain of PM1 and the output end of the antenna strength detection module, and the C1 is connected in series between the output end of the antenna strength detection module and the ground;

[0092] The source of PM1 is connected to the gate and drain of PM2 and the gate and drain of PM3 respectively;

[0093] The source of PM2 is connected to one antenna receiving end, and the source of PM3 is connected to another antenna receiving end, forming a rectifying power supply part.

[0094] The PMOS tube PM1 combines with the reference voltage VREF2 to form the source input amplifier. When the antenna voltage increases, the current at the source and drain of PM1 increases rapidly, charging the capacitor C1 through the load resistor R1, and the output voltage V1 increases. The corresponding time constant τ is shown in the following formula (1):

[0095] τ=R1*C1 (1)

[0096] The setting of the time constant τ is related to the low level duration τ of the card reader sending data 0 The time constant τ should be significantly higher than τ 0 , so as to truly reflect the antenna signal strength level without interference from data communications.

[0097] The antenna strength detection module has a simple structure, high reliability and fast response speed.

[0098] Reference voltage generation module such as Figure 5 As shown, VREC is the input signal, which is a DC power supply obtained by the other functional circuits 13 of the AFE (analog front end) after rectification and filtering. VREF1 and VREF2 are output signals, which are respectively used as the second voltage value input to the comparator 4 and the reference voltage of the antenna signal input to the antenna strength detection module 2. Among them, the NMOS tube NM1, the NMOS tube NM2, the PMOS tube PM3, the PMOS tube PM4 and the resistor R2 together constitute a PTAT current source that is independent of the power supply and proportional to the temperature. The PMOS tube PM5 and the PMOS tube PM6 constitute a mirror current source, and the current passes through the resistors R3, R4 and the diode-connected PNP transistors PNP1 and PNP2 to respectively constitute the reference voltages VREF1 and VREF2. Since the reference current is proportional to the temperature, the diode-connected PNP tube voltage is inversely proportional to the temperature, thereby constituting VREF1 and VREF2 that do not change with temperature and power supply.

[0099] According to one embodiment of this specification, Figure 6 As shown, the comparator 4 includes an operational amplifier OPA and a variable resistor divider 41;

[0100] The first input terminal of the operational amplifier OPA is connected to the first input terminal of the comparator 4, and the output terminal of the operational amplifier OPA is connected to the output terminal of the comparator 4;

[0101] The output terminal of the operational amplifier OPA and the second input terminal of the comparator 4 provide a variable second voltage value VREF3 to the second input terminal of the operational amplifier OPA through the variable resistor divider 41 .

[0102] By having a variable resistor divider 41, a smaller reference voltage VREF3 is selected when the antenna signal strength is strong, and a larger reference voltage VREF3 is selected when the antenna signal strength is weak, in order to prevent malfunction caused by small ripples and small glitches of the first voltage value V1 signal and improve the reliability of judgment.

[0103] Specifically, the variable resistor voltage divider 41 includes a plurality of resistors, at least one resistor has a voltage divider switch connected in parallel at both ends, and the output end of the operational amplifier OPA is connected to the control end of the voltage divider switch. Therefore, when the antenna signal strength is strong, the first voltage value V1 is high, the operational amplifier OPA outputs a high-level signal, controls the voltage divider switch S5 to close, thereby short-circuiting the resistor corresponding to the voltage divider switch, and reducing the voltage value of the second input terminal VREF3 of the operational amplifier OPA. When the antenna signal strength is weak, the first voltage value V1 is low, the operational amplifier OPA outputs a low-level signal, controls the voltage divider switch S5 to be disconnected, and the resistor corresponding to the voltage divider switch works, thereby increasing the voltage value of the second input terminal VREF3 of the operational amplifier OPA.

[0104] Furthermore, if Figure 6 As shown, the variable resistor divider 41 includes resistors R4, R5 and R6; R4, R5 and R6 are connected in series.

[0105] The R4 is connected in series between the second input terminal of the comparator 4 and the second input terminal of the operational amplifier OPA;

[0106] The R5 and R6 are connected in series, and are connected in series between the second input terminal of the operational amplifier OPA and the ground;

[0107] The two ends of R6 are connected in parallel with the voltage divider switch S5.

[0108] When the coil antenna signal strength is strong, the first voltage value V1 is high, the output of the operational amplifier OPA is high, the voltage divider switch S5 is closed, and the VREF3 voltage value Va is as shown in the following formula (2); when the coil antenna signal strength is weak, the first voltage value V1 is low, the output of the operational amplifier OPA is low, the voltage divider switch S5 is disconnected, and the VREF3 voltage value Vb is as shown in the following formula (3).

[0109] Va=VREF1*R5 / (R4+R5) (2)

[0110] Vb=VREF1*(R5+R6) / (R4+R5+R6) (3)

[0111] Obviously, Vb is greater than Va. Therefore, when the coil antenna signal strength is strong, a smaller reference voltage Va is selected, and when the coil antenna signal strength is weak, a larger reference voltage Vb is selected.

[0112] Based on the same inventive concept, an embodiment of the present specification further provides a chip on which the high-reliability RFID backscatter modulation circuit described in the embodiment of the present specification is formed.

[0113] It should be understood that in the various embodiments of this document, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this document.

[0114] It should also be understood that in the embodiments of this article, the term "and / or" is only a description of the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0115] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this article.

[0116] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0117] In the several embodiments provided herein, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or can be electrical, mechanical or other forms of connection.

[0118] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of this article.

[0119] In addition, each functional unit in each embodiment of this invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of software functional unit.

[0120] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this article is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of this article. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0121] Specific embodiments are used in this article to illustrate the principles and implementation methods of this article. The description of the above embodiments is only used to help understand the methods and core ideas of this article. At the same time, for general technicians in this field, according to the ideas of this article, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on this article.

Claims

1. A high reliability RFID backscatter modulation circuit, characterized in that: It includes an RFID basic module, an antenna strength detection module, a reference voltage generation module, a comparator and an adjustable impedance switch; The antenna strength detection module is used to output a first voltage value according to the antenna signal strength of the two antenna receiving ends in the RFID basic module; The reference voltage generating module is used to generate a stable second voltage value; The adjustable impedance switch includes a multi-way switch resistor connected in parallel between the two antenna receiving ends, the switch state of the switch resistor is controlled by the data signal sent by the RFID basic module, at least one switch resistor in the multi-way switch resistor has a transmission switch, and the transmission switch is used to control the transmission of the data signal of the corresponding switch resistor; The comparator is used to control the switching state of the transmission switch according to the first voltage value and the second voltage value.

2. The high reliability RFID backscatter modulation circuit according to claim 1, characterized in that: The comparator is used for controlling the transmission switch to be closed when the first voltage value is higher than the second voltage value, and vice versa, controlling the transmission switch to be opened.

3. The high reliability RFID backscatter modulation circuit according to claim 1, characterized in that: The multi-way switch resistor is a two-way switch resistor, wherein only one of the switch resistors has the transmission switch.

4. The high reliability RFID backscatter modulation circuit according to claim 1, characterized in that: The transmission switch includes a first inverter, a second inverter, a first switch and a second switch; A first end of the first inverter is connected to an output end of the comparator, a second end of the first inverter is connected to a first end of the second inverter, a second end of the second inverter is connected to a control end of the first switch, and the first switch is used to control the transmission of a data signal having a switch resistance of the transmission switch; The second end of the first inverter is also connected to the control end of the second switch, and the second switch is used to disconnect the switch resistor with the transmission switch when the switch state is closed.

5. The high reliability RFID backscatter modulation circuit according to claim 1, characterized in that: At least one switch resistor is composed of a plurality of resistors connected in series.

6. The high-reliability RFID backscatter modulation circuit according to claim 1, characterized in that: The antenna strength detection module includes a PMOS tube PM1, a PMOS tube PM2, a PMOS tube PM3, a resistor R1 and a capacitor C1; The gate of PM1 is used to input a reference voltage of an antenna signal, the resistor R1 is connected in series between the drain of PM1 and the output end of the antenna strength detection module, and the C1 is connected in series between the output end of the antenna strength detection module and the ground; The source of PM1 is connected to the gate and drain of PM2 and the gate and drain of PM3 respectively; The source of PM2 is connected to one antenna receiving end, and the source of PM3 is connected to another antenna receiving end.

7. The high reliability RFID backscatter modulation circuit according to claim 1, characterized in that: The output end of the antenna strength detection module is connected to the first input end of the comparator, and the output end of the reference voltage generation module is connected to the second input end of the comparator.

8. The high-reliability RFID backscatter modulation circuit according to claim 7, characterized in that: The comparator includes an operational amplifier and a variable resistor divider; The first input terminal of the operational amplifier is connected to the first input terminal of the comparator, and the output terminal of the operational amplifier is connected to the output terminal of the comparator; The output terminal of the operational amplifier and the second input terminal of the comparator provide a variable second voltage value to the second input terminal of the operational amplifier through the variable resistor divider.

9. The high-reliability RFID backscatter modulation circuit according to claim 8, characterized in that: The variable resistor voltage divider includes a plurality of resistors, at least one resistor has a voltage divider switch connected in parallel at both ends, and the output end of the operational amplifier is connected to the control end of the voltage divider switch.

10. The high-reliability RFID backscatter modulation circuit according to claim 9, characterized in that: The variable resistor divider includes resistors R4, R5 and R6; The R4 is connected in series between the second input terminal of the comparator and the second input terminal of the operational amplifier; The R5 and R6 are connected in series, and are connected in series between the second input terminal of the operational amplifier and the ground; The two ends of R6 are connected in parallel with the voltage divider switch.

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