Processor-free high-signal-to-noise-ratio backscattering label and method

Abstract

The invention discloses a processor-free high-signal-to-noise-ratio backscattering label in the field of backscattering label communication, which comprises a crystal oscillator unit, a pulse width modulation unit, an isolation unit, an on-off unit, an oscillation control unit, a radio frequency switch and a radio frequency energy collection module, the radio frequency energy collection module is used for converting a carrier signal transmitted by the transmitter into a direct current signal and stabilizing the voltage, and the radio frequency energy collection module is also used for supplying power to the crystal oscillator unit, the pulse width modulation unit, the oscillation control unit and the radio frequency switch; the invention also provides a backscattering method. The beneficial effects of the invention are that through the pulse width modulation unit and the voltage-controlled oscillator, a backscattering signal is converted from an existing amplitude modulation signal to a frequency modulation signal, the stability and the signal-to-noise ratio of the backscattering signal are greatly improved, and the power consumption is lower.

Description

Technical Field

[0001] The present invention relates to the technical field of backscatter tag communication, and in particular to a processor-free high signal-to-noise ratio backscatter tag and method. Background Art

[0002] Backscattering sensing technology is developed based on RFID sensing technology. Compared with RFID, it has a longer communication distance and supports high-concurrency multi-tag communication, and has greater application prospects in IoT communication methods. Backscattering technology is mainly divided into analog backscattering and digital backscattering. Digital backscattering has the advantages of strong anti-interference ability and the reflected signal is compatible with commercial equipment. However, digital backscattering technology requires the use of a high-power ADC to sample the output of the analog sensor, and the power consumption increases with the increase in sampling rate, which leads to an extremely low sampling rate of digital backscattering technology within 100Hz. Analog backscattering mainly uses amplitude modulation or resonant frequency demodulation technology to obtain sensor data. This modulation method will greatly limit the communication distance.

[0003] In order to solve the above problems, the team led by Professor James Rosenthal of the University of Washington proposed the following Figure 6 The PWM modulation technology diagram shown in the figure, the article published by the team is: Towards {Battery-Free} {HD} Video Streaming, the corresponding patent application name is: Image and / or video transmission using backscatter devices, patent number: US Patent 11,212,479. Its function is: to replace the high-power ADC with pulse width modulation technology (PWM) to perform ultra-low power consumption and high-rate sampling of analog sensors.

[0004] The principle of the above-mentioned prior art is: the microprocessor generates two signals, the first one is a sampling square wave, and the second one is a frequency shift signal. Then, the sampling square wave is input into the RC passive low-pass filter. After passing through the low-pass filter, the square wave is converted into a triangular wave with an amplitude between Vmax and Vmin. The triangular wave is input into the in-phase input of the comparator. At the same time, the analog voltage signal output by the sensor is input into the reverse input of the comparator. The PWM wave can be output at the output of the comparator. The duty cycle of the PWM wave is proportional to the amplitude of the sensor output voltage. Then, the PWM wave and the frequency shift signal are input into the XOR gate together to up-convert the PWM wave. The up-converted signal controls the on-off of the RF switch to realize backscattering. The amplitude of the generated backscattering signal remains unchanged, and the amplitude duration is proportional to the sensor output signal. It can be seen that the data sampling process of the sensor analog quantity does not require the participation of ADC, but is realized by a low-power comparator and passive devices, so the power consumption of the tag can be greatly reduced, and the amplitude of the generated analog backscattering signal is not affected by the sensor output amplitude, which can greatly improve the signal-to-noise ratio of the backscattering.

[0005] However, the backscatter signal generated by Professor James Rosenthal's solution is essentially an amplitude modulated signal. When demodulating the signal at the receiving end, the high and low levels of the amplitude are still used to obtain the PWM wave duty cycle of the demodulated signal. It is well known that the signal-to-noise ratio of the frequency modulated signal is higher than that of the amplitude modulated signal. The analog signal of the traditional frequency modulated analog backscattering technology sensor is proportional to the frequency change of the reflected signal. However, during the transmission process, the frequency of the signal is easily disturbed by the environment and becomes unstable.

[0006] To this end, we propose a processor-free high signal-to-noise ratio backscattering tag and method. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention provides a processor-free high signal-to-noise ratio backscattering tag.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0009] A processor-free high signal-to-noise ratio backscatter tag comprising:

[0010] A crystal oscillator unit, used to generate a square wave signal;

[0011] A pulse width modulation unit, used to convert the square wave signal generated by the crystal oscillator unit into a triangular wave signal, and compare the converted triangular wave signal with the voltage signal output by the analog sensor, and also used to convert the voltage signal output by the analog sensor into a PWM wave signal proportional to the voltage signal;

[0012] An isolation unit, used for separating the DC component of the PWM wave signal output by the pulse width modulation unit;

[0013] A switching unit, used for receiving the PWM wave signal output by the isolation unit and controlling its own switching according to the PWM wave signal;

[0014] An oscillation control unit, used for generating square waves of different frequencies according to the on / off switching of the on / off unit;

[0015] A radio frequency switch receives the square wave generated by the oscillation control unit and performs a switching action at the same frequency as the square wave generated by the oscillation control unit and reflects the backscattered signal to the receiver, and the receiver is used to receive and demodulate the backscattered signal output by the radio frequency switch;

[0016] A radio frequency energy collection module, used to convert the carrier signal transmitted by the transmitter into a DC signal and stabilize the voltage. The radio frequency energy collection module is also used to supply power to the crystal oscillator unit, the pulse width modulation unit, the oscillation control unit and the radio frequency switch;

[0017] The receiver is used to receive and demodulate the backscattered signal output by the RF switch.

[0018] Through the pulse width modulation unit and the oscillation control unit, the backscattered signal is converted into a signal including two frequency components. The duration of the two frequency components of the signal is proportional to the amplitude of the signal of the analog sensor. The backscattered signal is essentially a frequency modulated signal, which greatly improves the stability and signal-to-noise ratio of the backscattered signal. It does not require a microprocessor, further reducing the power consumption of the tag.

[0019] It is further defined that the pulse width modulation unit includes an RC passive low-pass filter and a comparator, the input end of the RC passive low-pass filter is electrically connected to the crystal oscillator unit, the output end of the RC passive low-pass filter is electrically connected to the input end of the comparator, and the output end of the analog sensor is also electrically connected to the input end of the comparator.

[0020] It is further defined that the isolation unit is a coupling capacitor, and an input end of the coupling capacitor is electrically connected to an output end of the comparator.

[0021] It is further defined that the on-off unit is an NMOS tube, and an input end of the NMOS tube is electrically connected to an output end of the coupling capacitor.

[0022] It is further defined that the oscillation control unit is a voltage-controlled oscillator, the input end of the voltage-controlled oscillator is electrically connected to the output end of the NMOS tube, and the output end of the voltage-controlled oscillator is electrically connected to the input end of the radio frequency switch.

[0023] It is further defined that the oscillation control unit is a voltage-controlled oscillator, the input end of the voltage-controlled oscillator is electrically connected to the output end of the NMOS tube, and the output end of the voltage-controlled oscillator is electrically connected to the input end of the radio frequency switch.

[0024] It is further defined that the radio frequency switch includes a high-level switch, a low-level switch, a load circuit and an antenna, the high-level switch is arranged on the transmission line between the input end of the radio frequency switch and the antenna, the low-level switch is arranged on the load circuit, and the load circuit is arranged on the transmission line between the high-level switch and the antenna.

[0025] A backscattering method, using the above-mentioned processor-free high signal-to-noise ratio backscattering tag, comprises the following steps:

[0026] S1: The crystal oscillator unit generates a square wave with a frequency of f1, which is input into the RC passive low-pass filter in the pulse width modulation unit. The RC passive low-pass filter converts the square wave with a frequency of f1 into a triangle wave with a frequency of f1;

[0027] S2: The triangular wave of frequency f1 and the voltage signal output by the analog sensor are input into the comparator, and the comparator converts the voltage value of the analog sensor into a PWM wave that is proportional to it;

[0028] S3: The PWM wave in step S2 is input to the coupling capacitor, which filters out the DC component of the PWM wave and controls whether the NMOS tube is turned on or off;

[0029] S4: When the gate of the NMOS tube is at a low level, it is turned on, so that the voltage-controlled oscillator generates a square wave with a frequency of f2, and controls the RF switch to switch at the frequency of f2; when the gate of the NMOS tube is at a high level, it is turned off, so that the voltage-controlled oscillator generates a square wave with a frequency of f3, and controls the RF switch to switch at the frequency of f3;

[0030] S5: Use the transmitter to transmit a single tone signal with a frequency of f0. When the RF switch is switched at a frequency of f2, a backscatter signal with a frequency of f0±f2 is generated; when the RF switch is switched at a frequency of f3, a backscatter signal with a frequency of f0±f3 is generated.

[0031] S6: Use a receiver to receive the backscattered signal and filter and demodulate it. The demodulation result is a PWM wave output by the comparator.

[0032] S7: The sensing value of the sensor is obtained by inversely calculating the relationship between the PWM wave duty cycle and the analog voltage of the analog sensor.

[0033] It is further defined that the specific steps of step S4 are: when the input of the RF switch is at a high level, the high level switch is turned on and the low level switch is turned off; when the input of the RF switch is at a low level, the high level switch is turned off and the low level switch is turned on to connect the load of the load circuit.

[0034] It is further defined that the filtering in step S6 is specifically filtering out the backscattered signal composed of the frequency components of f0-f2 and f0-f3 through a bandpass filter, leaving only the backscattered signal composed of the frequency components of f0+f2 and f0+f3.

[0035] The beneficial effects of the present invention are: through the pulse width modulation unit and the voltage-controlled oscillator, the backscattered signal is converted from the existing amplitude modulation signal to a frequency modulation signal, which greatly improves the stability and signal-to-noise ratio of the backscattered signal and has lower power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a connection schematic diagram of the present invention;

[0037] Figure 2 Schematic diagram of the steps of the backscattering method;

[0038] Figure 3 It is a simple schematic diagram of the entire backscatter system;

[0039] Figure 4 It is the frequency domain diagram of the backscattered signal;

[0040] Figure 5 It is a schematic diagram of the relationship between the backscattering time domain waveform and the demodulated waveform and the frequency duration;

[0041] Figure 6 It is a schematic diagram of the prior art in the background technology.

[0042] The symbols of the components are as follows:

[0043] Crystal oscillator unit 1, pulse width modulation unit 2, RC passive low-pass filter 21, comparator 22, analog sensor 3, isolation unit 4, pass-through unit 5, oscillation control unit 6, radio frequency switch 7, high level switch 71, low level switch 72, load circuit 73, antenna 74, radio frequency energy collection module 8, transmitter 9, receiver 10. DETAILED DESCRIPTION

[0044] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0045] Example:

[0046] like Figure 1-Figure 6As shown, a processor-free high signal-to-noise ratio backscatter tag includes a crystal oscillator unit 1, a pulse width modulation unit 2, an analog sensor 3, an isolation unit 4, a pass-through unit 5, an oscillation control unit 6, a radio frequency switch 7 and a radio frequency energy collection module 8; the crystal oscillator unit 1 is used to generate a square wave signal; the pulse width modulation unit 2 includes an RC passive low-pass filter 21 and a comparator 22, the input end of the RC passive low-pass filter 21 is electrically connected to the crystal oscillator unit 1, the output end of the RC passive low-pass filter 21 is electrically connected to the input end of the comparator 22, and the output end of the analog sensor 3 is also electrically connected to the input end of the comparator 22; The pulse width modulation unit 2 is used to convert the square wave signal generated by the crystal oscillator unit 1 into a triangular wave signal, and compare the converted triangular wave signal with the voltage signal output by the analog sensor 3, and also used to convert the voltage signal output by the analog sensor 3 into a PWM wave signal proportional to it; the isolation unit 4 is a coupling capacitor, and the input end of the coupling capacitor is electrically connected to the output end of the comparator 22; the isolation unit 4 is used to separate the DC component of the PWM wave signal output by the pulse width modulation unit 2; the on-off unit 5 is an NMOS tube, and the input end of the NMOS tube is electrically connected to the output end of the coupling capacitor; the on-off unit 5 The oscillation control unit 6 is used to receive the PWM wave signal output by the isolation unit 4 and control its own on-off according to the PWM wave signal; the oscillation control unit 6 is a voltage-controlled oscillator, the input end of the voltage-controlled oscillator is electrically connected to the output end of the NMOS tube, and the output end of the voltage-controlled oscillator is electrically connected to the input end of the RF switch 7; the oscillation control unit 6 is used to generate square waves of different frequencies according to the on-off of the on-off unit 5; the RF switch 7 includes a high-level switch 71, a low-level switch 72, a load circuit 73 and an antenna 74, the high-level switch 71 is arranged on the transmission line between the input end of the RF switch 7 and the antenna 74, and the low-level switch 72 is arranged on the load circuit 73. The load circuit 73 is arranged on the transmission line between the high-level switch 71 and the antenna 74; the RF switch 7 receives the square wave generated by the oscillation control unit 6 and performs on-off action at the same frequency as the square wave generated by the oscillation control unit 6 and reflects the backscattered signal to the receiver 10, and the receiver 10 is used to receive and demodulate the backscattered signal output by the RF switch 7; the RF energy collection module 8 is used to convert the carrier signal transmitted by the transmitter 9 into a DC signal and stabilize the voltage, and the RF energy collection module 8 is also used to power the crystal oscillator unit 1, the pulse width modulation unit 2, the oscillation control unit 6 and the RF switch 7.

[0047] Through the pulse width modulation unit 2 and the oscillation control unit 6, the backscattered signal is converted into a signal including two frequency components. The duration of the two frequency components of the signal is proportional to the amplitude of the signal of the analog sensor 3. The backscattered signal is essentially a frequency modulated signal, which greatly improves the stability and signal-to-noise ratio of the backscattered signal, and does not require a microprocessor, further reducing the power consumption of the tag.

[0048] A backscattering method, using the above-mentioned processor-free high signal-to-noise ratio backscattering tag, comprises the following steps:

[0049] S1: The crystal oscillator unit 1 generates a square wave with a frequency of f1, which is input into the RC passive low-pass filter 21 in the pulse width modulation unit 2. The RC passive low-pass filter 21 converts the square wave with a frequency of f1 into a triangle wave with a frequency of f1;

[0050] S2: The triangular wave of frequency f1 and the voltage signal output by the analog sensor 3 are input into the comparator 22, and the comparator 22 converts the voltage value of the analog sensor 3 into a PWM wave that is proportional to the voltage value;

[0051] S3: The PWM wave in step S2 is input to the coupling capacitor, which filters out the DC component of the PWM wave and controls whether the NMOS tube is turned on or off;

[0052] S4: When the gate of the NMOS tube is at a low level, it is turned on. At this time, only one resistor is connected between the voltage-controlled oscillator and the ground terminal, so that the voltage-controlled oscillator generates a square wave with a frequency of f2. At this time, due to the low level input at the oscillator end, the high-level switch 71 of the RF switch 7 is disconnected, and the low-level switch 72 is turned on to connect the load of the load circuit 73, and the low-level switch 72 is switched at a frequency of f2; when the gate of the NMOS tube is at a high level, it is cut off. At this time, both resistors between the voltage-controlled oscillator and the ground terminal are connected to the voltage-controlled oscillator, so that the voltage-controlled oscillator generates a square wave with a frequency of f3. At this time, due to the high level input at the oscillator end, the high-level switch 71 of the RF switch 7 is turned on, and the low-level switch 72 is disconnected, and the high-level switch 71 is switched at a frequency of f3;

[0053] S5: Use the transmitter 9 to transmit a single tone signal with a frequency of f0. When the radio frequency switch 7 is switched at a frequency of f2, a backscattered signal with a frequency of f0±f2 is generated; when the radio frequency switch 7 is switched at a frequency of f3, a backscattered signal with a frequency of f0±f3 is generated;

[0054] S6: using the receiver 10 to receive the backscattered signal and filtering out the backscattered signal composed of the frequency components of f0-f2 and f0-f3 through a bandpass filter, leaving only the backscattered signal composed of the frequency components of f0+f2 and f0+f3, and then demodulating the backscattered signal composed of the frequency components of f0+f2 and f0+f3, the demodulation result is the PWM wave output by the comparator 22;

[0055] S7: The sensor's sensing value is obtained by reversely calculating the relationship between the PWM wave duty cycle and the analog voltage of the analog sensor 3.

Claims

1. A processor-free high signal-to-noise ratio backscatter tag, characterized in that: include: A crystal oscillator unit (1), used to generate a square wave signal; A pulse width modulation unit (2) is used to convert the square wave signal generated by the crystal oscillator unit (1) into a triangular wave signal, compare the converted triangular wave signal with the voltage signal output by the analog sensor (3), and convert the voltage signal output by the analog sensor (3) into a PWM wave signal that is proportional to the voltage signal; An isolation unit (4) for separating the DC component of the PWM wave signal output by the pulse width modulation unit (2); A switching unit (5) is used to receive the PWM wave signal output by the isolation unit (4) and control its own switching according to the PWM wave signal; An oscillation control unit (6), used for generating square waves of different frequencies according to the on / off switching of the on / off switching unit (5); A radio frequency switch (7) receives the square wave generated by the oscillation control unit (6) and performs a switching action at the same frequency as the square wave generated by the oscillation control unit (6) and reflects a backscattered signal to a receiver, wherein the receiver (10) is used to receive and demodulate the backscattered signal output by the radio frequency switch (7); A radio frequency energy collection module (8) is used to convert a carrier signal emitted by a transmitter (9) into a direct current signal and stabilize the voltage; the radio frequency energy collection module (8) is also used to supply power to a crystal oscillator unit (1), a pulse width modulation unit (2), an oscillation control unit (6) and a radio frequency switch (7).

2. The processor-free high signal-to-noise ratio backscatter tag according to claim 1, characterized in that: The pulse width modulation unit (2) comprises an RC passive low-pass filter (21) and a comparator (22); the input end of the RC passive low-pass filter (21) is electrically connected to the crystal oscillator unit (1); the output end of the RC passive low-pass filter (21) is electrically connected to the input end of the comparator (22); and the output end of the analog sensor (3) is also electrically connected to the input end of the comparator (22).

3. The processor-free high signal-to-noise ratio backscatter tag according to claim 2, characterized in that: The isolation unit (4) is a coupling capacitor, and the input end of the coupling capacitor is electrically connected to the output end of the comparator (22).

4. The processor-free high signal-to-noise ratio backscatter tag according to claim 3, characterized in that: The on-off unit (5) is an NMOS tube, and the input end of the NMOS tube is electrically connected to the output end of the coupling capacitor.

5. The processor-free high signal-to-noise ratio backscatter tag according to claim 4, characterized in that: The oscillation control unit (6) is a voltage-controlled oscillator, the input end of the voltage-controlled oscillator is electrically connected to the output end of the NMOS tube, and the output end of the voltage-controlled oscillator is electrically connected to the input end of the radio frequency switch (7).

6. The processor-free high signal-to-noise ratio backscatter tag according to claim 5, characterized in that: The radio frequency switch (7) comprises a high-level switch (71), a low-level switch (72), a load circuit (73) and an antenna (74); the high-level switch (71) is arranged on a transmission line between an input end of the radio frequency switch (7) and the antenna (74); the low-level switch (72) is arranged on the load circuit (73); and the load circuit (73) is arranged on a transmission line between the high-level switch (71) and the antenna (74).

7. A backscattering method, using a processor-free high signal-to-noise ratio backscattering tag as claimed in any one of claims 1 to 6, characterized in that: The steps include: S1: The crystal oscillator unit (1) generates a square wave with a frequency of f1, which is input into the RC passive low-pass filter (21) in the pulse width modulation unit (2). The RC passive low-pass filter (21) converts the square wave with a frequency of f1 into a triangle wave with a frequency of f1; S2: The triangular wave of frequency f1 and the voltage signal output by the analog sensor (3) are input into the comparator (22), and the comparator (22) converts the voltage value of the analog sensor (3) into a PWM wave proportional to the voltage value; S3: The PWM wave in step S2 is input to the coupling capacitor, which filters out the DC component of the PWM wave and controls whether the NMOS tube is turned on or off; S4: when the gate of the NMOS tube is at a low level, it is turned on, so that the voltage-controlled oscillator generates a square wave with a frequency of f2, and controls the radio frequency switch (7) to switch at the frequency of f2; when the gate of the NMOS tube is at a high level, it is turned off, so that the voltage-controlled oscillator generates a square wave with a frequency of f3, and controls the radio frequency switch (7) to switch at the frequency of f3; S5: using a transmitter (9) to transmit a single tone signal with a frequency of f0, when the radio frequency switch (7) is switched at a frequency of f2, a backscattered signal with a frequency of f0±f2 is generated; when the radio frequency switch (7) is switched at a frequency of f3, a backscattered signal with a frequency of f0±f3 is generated; S6: using the receiver (10) to receive the backscattered signal and filter and demodulate it, the demodulation result is the PWM wave output by the comparator (22); S7: The sensor's sensing value is obtained by reversely calculating the relationship between the PWM wave duty cycle and the analog voltage of the analog sensor (3).

8. The backscattering method according to claim 7, characterized in that: The specific step S4 is that when the input of the radio frequency switch (7) is at a high level, the high level switch (71) is turned on and the low level switch (72) is turned off; when the input of the radio frequency switch (7) is at a low level, the high level switch (71) is turned off and the low level switch (72) is turned on to connect the load of the load circuit (73).

9. The backscattering method according to claim 7, characterized in that: The filtering in step S6 is specifically to filter out the backscattered signal composed of the frequency components of f0-f2 and f0-f3 through a bandpass filter, leaving only the backscattered signal composed of the frequency components of f0+f2 and f0+f3.

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