Energy collection sensing label

Abstract

The invention relates to an energy collection sensing tag, and belongs to the technical field of RFID tags, and the energy collection sensing tag comprises an antenna, a switch S, an RF energy collection circuit, a UHF RFID chip and a time-sharing controller. The antenna is used for receiving a radio frequency energy signal and is connected with the RF energy collection circuit or the UHF RFID chip through the switch S; the RF energy collection circuit or the UHF RFID chip is connected with the time-sharing controller, and the time-sharing controller outputs a control signal SW to control the switch S to perform switching. The tag structure is designed based on the time-sharing working principle, the original energy charging sensitivity and receiving sensitivity of the tag circuit are kept not to be reduced, the energy collection effect and the sensitivity of the RFID chip are both considered, and the problem that the receiving sensitivity and the energy charging sensitivity of the whole tag are reduced or the antenna port matching is poor in a traditional scheme is solved.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of RFID tags, and in particular relates to an energy harvesting sensor tag. Background Art

[0002] To reduce manufacturing and operating costs, current UHF RFID tags in commercial and consumer applications mostly utilize a single chip and antenna combination. This chip incorporates a rectifier circuit, which rectifies and converts the RF energy signal collected by the antenna into a stable voltage during RFID (Radio Frequency Identification) communications, providing DC power for the chip. The voltage envelope output by the rectifier circuit is then fed to a demodulator circuit, which then decodes the command signal sent by the gateway. The demodulation sensitivity of the RFID chip is limited by the stability of its power supply. Proper power supply depends on the performance of the rectifier circuit, which also has to take into account the extraction of the voltage envelope signal, resulting in low conversion efficiency.

[0003] In many industrial scenarios, it's necessary to collect sensor information from multiple nodes. This information is then transmitted to user devices via communication systems such as RFID, LoRa, and WiFi. RFID technology offers the following advantages: tags utilize backscatter technology, require no external batteries, are easy to maintain, and are inexpensive. Consequently, RFID technology is gaining increasing attention in the field of industrial sensor communications.

[0004] At the same time, this new application area requires the label to have the following performance:

[0005] 1) High demodulation sensitivity, capable of stable communication at distances of 10m and above;

[0006] 2) High power supply sensitivity, which can meet the power requirements of wireless communication and sensor power supply.

[0007] 3) Relatively compact size.

[0008] To meet the above three characteristics, the tag must integrate not only the RFID chip but also an RF energy harvesting circuit. This circuit has higher efficiency and higher rectification sensitivity than the rectifier circuit in the RFID chip, and can provide DC power to the RFID chip and sensor over a larger input dynamic range. At the same time, most of the tag area is occupied by the antenna. Both the RF energy harvesting circuit and the RFID chip need to obtain signals from the antenna. If two antennas are used to connect the RF energy harvesting circuit and the RFID chip respectively, the tag size will more than double compared to a single antenna, and there will also be coupling issues between the two antennas.

[0009] Currently, there are two main solutions to solve the problem of RF energy harvesting circuits and RFID chips sharing a single antenna: fixed power allocation and variable power allocation.

[0010] 1) Fixed power allocation

[0011] The tag structure diagram based on fixed power allocation is as follows Figure 1 As shown, a two-way power splitter with a specific power distribution ratio is used. The input of the power splitter is connected to the antenna, and the two outputs are connected to the RF energy harvesting circuit and the RFID chip, respectively. When the RF energy harvesting circuit collects enough power, it begins to power the RFID chip and sensor, meeting the requirements of RFID communication and sensor information collection.

[0012] Assuming the signal power received by the antenna is Pant (dBm), the power splitter network attenuates A1 and A2 (dB) respectively. The signal power received by the RF energy harvester and the RFID chip is: Pant-A1, Pant-A2 (dBm) respectively. A2 can be converted based on the A1 value as follows:

[0013] A2=-10*log(1-10^(-A1 / 10))

[0014] In this mode, the tag's receiving sensitivity is reduced by A2 (dB), the bidirectional communication link between the tag and the reader is reduced by 2*A2 (dB), and the tag's RF energy harvesting charging sensitivity is reduced by A1 (dB).

[0015] 2) Unfixed power allocation

[0016] The tag structure diagram based on non-fixed power allocation is as follows Figure 2 As shown in the figure, the power divider's input is connected to the antenna, and its two outputs are connected to the RF energy harvesting circuit and the RFID chip, respectively. When the RF energy harvesting circuit collects enough power, it starts to supply power to the RFID chip and sensor, meeting the requirements of RFID communication and sensor information collection.

[0017] Matching circuit 2 matches the input impedance of the UHF RFID chip to Z2, while matching circuit 1 matches the input impedance of the RF energy harvesting circuit to Z1. Matching circuits 1 and 2 are connected to a common input node. By distributing the impedances of Z1 and Z2, the specified power is distributed to the UHF transceiver and energy harvesting circuit. Matching circuit 3 matches the parallel impedance of Z1 / / Z2, Z1 and Z2, to the antenna port impedance.

[0018] Due to the nonlinearity of the RF energy harvesting circuit and the RFID chip, Z1 and Z2 will vary with input power, making matching circuit design difficult. Furthermore, the power allocation ratio will vary with the signal power received by the antenna. The design of Z1 and Z2 can only be based on a specific input power point, thus achieving power allocation only for a known input power. Furthermore, the lack of mutual isolation between the Z1 and Z2 ports means that some of the RFID chip's reverse transmission signal will be fed back into the RF energy harvesting circuit.

[0019] Compared to conventional power splitter networks, this circuit has the advantage that some of the energy lost in the RFID chip's transmitted signal is not converted into heat loss, but instead is input into the energy harvesting circuit. In contrast, the transmitted signal of a conventional power splitter network is lost in the power splitter's isolation resistor. A disadvantage is that performance is optimal only at certain power points. Beyond these power points, the input impedance of the RF energy harvesting circuit and the RFID chip varies, resulting in poor antenna port matching.

[0020] Generally speaking, fixed power allocation reduces both the tag's receiving sensitivity and charging sensitivity. Non-fixed power allocation complicates matching circuit design and optimizes performance only at specific power points. Beyond these specific power points, the input impedance of the RF energy harvesting circuit and the RFID chip varies, leading to poor matching between the antenna port and the antenna.

[0021] Therefore, it is necessary to provide a new energy harvesting sensor tag to solve the above technical problems. Summary of the Invention

[0022] The purpose of the present disclosure is to provide an energy harvesting sensor tag in order to solve the above problems.

[0023] The present disclosure achieves the above objectives through the following technical solutions:

[0024] An energy harvesting sensor tag includes an antenna, a switch S, an RF energy harvesting circuit, a UHF RFID chip and a time-sharing controller;

[0025] The antenna is used to receive radio frequency energy signals and is connected to the RF energy harvesting circuit or the UHF RFID chip through the switch S. At the same time point, the received radio frequency energy signal is transmitted to one of the two. The RF energy harvesting circuit or the UHF RFID chip is connected to the time-sharing controller. The time-sharing controller outputs a control signal SW to control the switch S to switch. The RF energy harvesting circuit provides a DC power supply for the UHF RFID chip and the time-sharing controller.

[0026] As a further optimization solution of the present disclosure, in the initial state, the energy collected by the RF energy harvesting circuit is 0, and the switch S remains connected to the RF energy harvesting circuit in an unpowered state.

[0027] As a further optimization solution of the present disclosure, the switch S is connected to the RF energy harvesting circuit by default. The antenna transmits the received radio frequency energy signal to the RF energy harvesting circuit, and the energy is stored in the energy storage capacitor. After collecting a preset value of energy, the RF energy harvesting circuit supplies power to the time-sharing controller and the UHF RFID chip respectively. The time-sharing controller starts working and outputs a control signal SW.

[0028] When the control signal SW is at the H level, the switch S switches to connect to the UHF RFID chip; when the voltage of the energy storage capacitor drops to a threshold, the control signal SW returns to the L level, and the switch S switches to reconnect the antenna to the RF energy collection circuit.

[0029] As a further optimization solution of the present disclosure, the switch S includes a switch S1, a switch S2, and a transmission line with a characteristic impedance of 1 / 4 carrier wavelength Z0; when the switch S1 and the switch S2 are disconnected, the antenna is connected to the RF energy harvesting circuit; when the switch S1 and the switch S2 are closed, the antenna is connected to the UHF RFID chip.

[0030] As a further optimization solution of the present disclosure, the switch S1 and the switch S2 are both low-power PIN diodes.

[0031] As a further optimization solution of the present disclosure, when power is not supplied, the switch S1 and the switch S2 are both open, and the antenna transmits the radio frequency energy signal directly to the RF energy harvesting circuit. When a preset value of energy is harvested, the RF energy harvesting circuit starts to supply power, and the time-sharing controller starts to output an H level to the switch S1 and the switch S2, and the switch S1 and the switch S2 are both closed and turned on.

[0032] When the switch S2 is in the closed state, the input end of the RF energy collection circuit is short-circuited, and the RF energy signal received by the antenna will not enter the RF energy collection circuit; at the same time, due to the existence of the 1 / 4 carrier wavelength transmission line, the switch S1 node is equivalent to an open circuit; when the switch S1 is in the closed state, the RF energy signal received by the antenna all enters the UHF RFID chip.

[0033] As a further optimization solution of the present disclosure, the switch S includes a switch S1, a switch S2 and a π-type filter circuit, and the π-type filter circuit includes a capacitor C1, an inductor L1 and a capacitor C2; when the switch S1 and the switch S2 are disconnected, the antenna is connected to the RF energy collection circuit; when the switch S1 and the switch S2 are closed, the antenna is connected to the UHF RFID chip.

[0034] As a further optimization solution of the present disclosure, the values of the capacitor C1, the inductor L1, and the capacitor C2 are as follows:

[0035]

[0036] Wherein, L represents the inductance value of the inductor L1, C represents the capacitance values of the capacitor C1 and the capacitor C2; w0 represents the carrier center angular frequency.

[0037] As a further optimization solution of the present disclosure, the switch S1 is composed of a resistor R1, a diode D1, an inductor L2, and a capacitor C3; the inductor L2 provides choke for the RF energy signal and provides a DC path for the diode; the resistor R1 is a current-limiting resistor and prevents the RF energy signal from entering the time-sharing controller;

[0038] The switch S2 is composed of a resistor R2 and a diode D2; the resistor R2 is a current-limiting resistor and prevents the radio frequency energy signal from entering the time-sharing controller.

[0039] As a further optimization solution of the present disclosure, in the initial state, the circuit is not powered on and the control signal SW is at an L level; when the voltage across the diode D1 and the diode D2 is 0V, the parallel resistance value of the diode D1 and the diode D2 can reach a preset value; when the antenna senses the RF energy signal, the RF energy signal will not enter the UHF RFID chip, and the diode D2 will not absorb the RF energy signal; the RF energy signal will all enter the RF energy collection circuit, and the electrical energy converted by the RF energy collection circuit will charge the energy storage capacitor;

[0040] When the voltage on the energy storage capacitor is greater than the threshold, the voltage stabilizing circuit starts supplying power, and the UHF RFID chip circuit starts operating. Then, the time-sharing controller responds. When the timing reaches the specified time T0, the time-sharing controller outputs a high-level control signal SW to control the conduction of the diodes D1 and D2. Since the impedance of the diode D2 after conduction is close to 0, the RF energy signal is totally reflected back at the diode D2. At the same time, the diode D1 is turned on, and the RF energy signal is transmitted to the UHF RFID chip through the diode D1 and capacitor C3.

[0041] When the RF energy signal is sent by the gateway and is a command signal, the UHF RFID chip starts to respond, collects sensor data, and reflects it through the UHF wireless channel. The gateway receives the tag identification data and sensor data transmitted by the tag, and a round of communication process is completed;

[0042] When the voltage on the energy storage capacitor is lower than the set threshold, the control signal SW is at a low level of 0V, and the system returns to the energy collection state.

[0043] The beneficial effects of the present disclosure are:

[0044] The present disclosure designs a tag structure based on the time-sharing working principle to maintain the original charging sensitivity and receiving sensitivity of the tag circuit, so that the energy collection effect and the sensitivity of the RFID chip can be taken into account, and solves the problems of reduced receiving sensitivity and charging sensitivity of the entire tag or poor antenna port matching in traditional solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the tag structure with fixed power allocation;

[0046] Figure 2 This is a schematic diagram of the tag structure with unfixed power allocation;

[0047] Figure 3 is a structural block diagram of an energy harvesting sensor tag in an embodiment of the present disclosure;

[0048] Figure 4 is a detailed schematic diagram of the tag switch structure in an embodiment of the present disclosure;

[0049] Figure 5 is a schematic diagram of an equivalent replacement of the tag transmission line structure in an embodiment of the present disclosure;

[0050] Figure 6 Schematic diagram of the refined structure of the energy harvesting sensor tag in the embodiment of the present disclosure. DETAILED DESCRIPTION

[0051] The present application will be described in further detail below in conjunction with the accompanying drawings. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0052] like Figure 3 As shown in FIG, an energy harvesting sensor tag structure designed based on the time-sharing working principle includes an antenna, a switch S, an RF energy harvesting circuit, a UHF RFID chip and a time-sharing controller.

[0053] The antenna is connected to only one functional circuit at a time: either the RF energy harvesting circuit or the UHF RFID chip. The signal sensed by the antenna enters only the RF energy harvesting circuit or the UHF RFID chip at any given time. The RF energy harvesting circuit provides DC power to the UHF RFID, time-sharing controller, and sensor. The time-sharing controller outputs a control signal to control the switching of switch S.

[0054] In the initial state, the RF energy harvesting circuit collects zero energy. For the tag to function properly, the switch S must be connected to the RF energy harvesting circuit even when it's not powered on. Conventional SPDT chips require a sufficient power supply voltage to function properly and cannot be used directly here. Therefore, a specially designed switch S circuit is required.

[0055] The time-sharing controller is used to allocate the time for the RF energy harvesting circuit and the UHF RFID chip to access the antenna respectively.

[0056] The time-sharing control strategy includes: S is connected to the RF energy harvesting circuit by default, and the RF energy signal sensed by the antenna is transmitted to the RF energy harvesting circuit. The energy is stored in a ceramic energy storage capacitor of tens to hundreds of microfarads. After collecting enough energy, the RF energy harvesting circuit can provide power to the time-sharing controller, UHF RFID chip, sensor, etc. The time-sharing controller starts working and outputs the control signal SW. When SW is at the H level, the switch S switches to the UHF RFID chip. The UHF RFID chip communicates with the sensor, obtains the sensor data, and communicates with the gateway. When the voltage of the energy storage capacitor drops to a level that is insufficient to support the power required for normal power supply of the tag, the time-sharing controller SW signal returns to the L level, and the antenna reconnects to the RF energy harvesting circuit.

[0057] By using a time-sharing mode, the charging sensitivity and receiving sensitivity of the tag will hardly decrease. The only decrease is the insertion loss of the switch S. The insertion loss of the RF switch S is usually very low, generally 0.2 to 0.5 dB.

[0058] Compared with the power distribution method, this type of time-sharing working method can maintain the original charging sensitivity and receiving sensitivity of the tag circuit.

[0059] The label structure of time-sharing work is refined as follows Figure 4 As shown in the figure, the structure of the RF switch is mainly refined. The RF switch S includes S1, S2, and a transmission line with a quarter carrier wavelength. S1 and S2 can be low-power PIN diodes.

[0060] The operating principle is as follows: When power is not supplied, S1 and S2 are open. The signal sensed by the antenna is directly transmitted to the RF energy harvesting circuit. When sufficient energy is harvested, the tag's power supply circuit begins to supply power to the tag circuit. The time-sharing controller begins to output an H level to S1 and S2, which then close and conduct.

[0061] When S2 is closed, the RF energy harvesting circuit input is short-circuited, preventing the signal received by the antenna from entering the energy harvesting circuit. Furthermore, due to the presence of the quarter-wavelength carrier transmission line, the node at switch S1 is effectively open-circuited. When S1 is closed, the entire signal sensed by the antenna enters the UHF RFID chip.

[0062] The entire control logic is summarized as follows:

[0063] SW is at H level, S1 and S2 are closed, the UHF RFID chip is connected to the antenna and starts working;

[0064] SW is at L level, S1 and S2 are disconnected, and the energy harvesting circuit is connected to the antenna and starts working.

[0065] Furthermore, in order to reduce the size of the tag, the 1 / 4 carrier wavelength transmission line with characteristic impedance Z_0 can be connected through an equivalent lumped parameter circuit such as Figure 5 as shown to further reduce the PCB size.

[0066] It can be derived from the following formula:

[0067]

[0068] The inductance and capacitance values can be calculated:

[0069]

[0070] Where Z0 is the characteristic impedance of the 1 / 4 wavelength transmission line, which is 50 ohms unless otherwise specified. w0 is the center angular frequency of the carrier. Figure 5 Equivalent circuit parameters at 0.925GHz and characteristic impedance of 50ohm.

[0071] A compact and highly sensitive energy harvesting sensor tag is designed and implemented as Figure 6 As shown, the tag includes an antenna, a 1 / 4 wavelength equivalent circuit, switches S1, S2 and their auxiliary circuits, an RF energy collection circuit, an energy storage capacitor, a voltage stabilization circuit, a sensor, a UHF RFID chip, and a time-sharing controller.

[0072] The 1 / 4 wavelength equivalent circuit is composed of inductors L1, C1, and C2, whose values are calculated using the aforementioned formulas (1) and (2).

[0073] Switch S1 consists of resistors R1, D1, L2, and C3. L2 chokes the RF energy signal and provides a DC path for the PIN diode. R1 is a current-limiting resistor that prevents the RF energy signal from entering circuits such as the time-sharing controller.

[0074] Switch S2 is composed of R2 and D2. R2 is a current-limiting resistor that also prevents RF energy signals from entering circuits such as the time-sharing controller.

[0075] D1 and D2 use PIN diodes, such as Infineon's BAR65, which only requires a current of 1.8V / 100uA to turn on D1 and D2.

[0076] The normal working process is as follows:

[0077] Initially, the tag's stored energy is insufficient, its circuitry is unpowered, and its SW pin is at a low level of 0V. When the voltage across D1 and D2 is 0V, the parallel resistance of D1 and D2 can reach 10kΩ. The antenna senses the RF energy signal, but it doesn't enter the UHF RFID chip. Furthermore, the high parallel resistance of D2 absorbs almost no RF energy. The entire RF energy signal enters the RF energy harvesting circuit, which then converts it into electrical energy that charges the energy storage capacitor.

[0078] When the voltage on the energy storage capacitor exceeds a certain threshold, the voltage regulator circuit begins to supply power to the tag. The sensor and UHF RFID chip circuits begin to operate. Then, the time-sharing controller responds. When the time reaches the specified time T0, the time-sharing controller outputs a high level to control D1 and D2 to conduct.

[0079] The SW output signal is high, and D1 and D2 are turned on. Since the impedance of D2 is very small after it is turned on, close to zero, the RF energy signal is fully reflected back from D2. At the same time, D1 is turned on, and the RF energy signal is transmitted to the UHF RFID chip through D1 and C3.

[0080] When the gateway sends a command signal, the UHF RFID chip circuit responds, collecting sensor data and reflecting it back through the UHF wireless channel. The gateway then receives the tag identification data and sensor data transmitted by the tag, completing a communication cycle.

[0081] When the voltage on the energy storage capacitor is lower than the set threshold, SW is low level 0 V. The tag returns to the energy collection state.

[0082] The above-described embodiments merely represent several implementation methods of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present disclosure. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the scope of the present disclosure, all of which fall within the scope of protection of the present disclosure.

Claims

1. An energy harvesting sensor tag, characterized in that: It includes an antenna, a switch S, an RF energy harvesting circuit, a UHF RFID chip and a time-sharing controller; The antenna is used to receive radio frequency energy signals and is connected to the RF energy harvesting circuit or the UHF RFID chip through the switch S. At the same time point, the received radio frequency energy signal is transmitted to one of the two. The RF energy harvesting circuit or the UHF RFID chip is connected to the time-sharing controller. The time-sharing controller outputs a control signal SW to control the switch S to switch. The RF energy harvesting circuit provides a DC power supply for the UHF RFID chip and the time-sharing controller.

2. The energy harvesting sensor tag according to claim 1, characterized in that: In the initial state, the energy collected by the RF energy harvesting circuit is 0, and the switch S remains connected to the RF energy harvesting circuit in an unpowered state.

3. The energy harvesting sensor tag according to claim 2, characterized in that: The switch S is connected to the RF energy harvesting circuit by default. The antenna transmits the received radio frequency energy signal to the RF energy harvesting circuit, and the energy is stored in the energy storage capacitor. After collecting a preset amount of energy, the RF energy harvesting circuit supplies power to the time-sharing controller and the UHF RFID chip respectively. The time-sharing controller starts working and outputs a control signal SW. When the control signal SW is at the H level, the switch S switches to connect to the UHF RFID chip; when the voltage of the energy storage capacitor drops to a threshold, the control signal SW returns to the L level, and the switch S switches to reconnect the antenna to the RF energy collection circuit.

4. The energy harvesting sensor tag according to claim 1, characterized in that: The switch S includes a switch S1, a switch S2, and a transmission line with a characteristic impedance of Z0 and a quarter carrier wavelength; when the switch S1 and the switch S2 are disconnected, the antenna is connected to the RF energy collection circuit; when the switch S1 and the switch S2 are closed, the antenna is connected to the UHF RFID chip.

5. The energy harvesting sensor tag according to claim 4, characterized in that: The switch S1 and the switch S2 are both low-power PIN diodes.

6. The energy harvesting sensor tag according to claim 4, characterized in that: In the unpowered state, the switch S1 and the switch S2 are both open, and the antenna transmits the radio frequency energy signal directly to the RF energy harvesting circuit. When a preset value of energy is harvested, the RF energy harvesting circuit starts to supply power, and the time-sharing controller starts to output an H level to the switch S1 and the switch S2, and the switch S1 and the switch S2 are both closed and turned on. When the switch S2 is in the closed state, the input end of the RF energy collection circuit is short-circuited, and the RF energy signal received by the antenna will not enter the RF energy collection circuit; at the same time, due to the existence of the 1 / 4 carrier wavelength transmission line, the switch S1 node is equivalent to an open circuit; when the switch S1 is in the closed state, the RF energy signal received by the antenna all enters the UHF RFID chip.

7. The energy harvesting sensor tag according to claim 1, characterized in that: The switch S includes a switch S1, a switch S2, and a π-type filter circuit, wherein the π-type filter circuit includes a capacitor C1, an inductor L1, and a capacitor C2; when the switch S1 and the switch S2 are disconnected, the antenna is connected to the RF energy harvesting circuit; when the switch S1 and the switch S2 are closed, the antenna is connected to the UHF RFID chip.

8. The energy harvesting sensor tag according to claim 7, characterized in that: The values of the capacitor C1, the inductor L1 and the capacitor C2 are as follows: Wherein, L represents the inductance value of the inductor L1, C represents the capacitance values of the capacitor C1 and the capacitor C2; w0 represents the carrier center angular frequency.

9. The energy harvesting sensor tag according to claim 8, characterized in that: The switch S1 is composed of a resistor R1, a diode D1, an inductor L2, and a capacitor C3; the inductor L2 provides choke for the RF energy signal and provides a DC path for the diode; the resistor R1 is a current limiting resistor and prevents the RF energy signal from entering the time-sharing controller; The switch S2 is composed of a resistor R2 and a diode D2; the resistor R2 is a current-limiting resistor and prevents the radio frequency energy signal from entering the time-sharing controller.

10. The energy harvesting sensor tag according to claim 9, characterized in that: In the initial state, the circuit is not powered on and the control signal SW is at an L level. When the voltage across the diode D1 and the diode D2 is 0V, the parallel resistance value of the diode D1 and the diode D2 can reach a preset value. When the antenna senses a radio frequency energy signal, the radio frequency energy signal does not enter the UHF RFID chip, and the diode D2 does not absorb the radio frequency energy signal. The radio frequency energy signal enters the RF energy collection circuit in its entirety, and the electrical energy converted by the RF energy collection circuit charges the energy storage capacitor. When the voltage on the energy storage capacitor is greater than the threshold, the voltage stabilizing circuit starts supplying power, and the UHF RFID chip circuit starts operating. Then, the time-sharing controller responds. When the timing reaches the specified time T0, the time-sharing controller outputs a high-level control signal SW to control the conduction of the diodes D1 and D2. Since the impedance of the diode D2 approaches 0 after conduction, the RF energy signal is totally reflected back at the diode D2. At the same time, the diode D1 is turned on, and the RF energy signal is transmitted to the UHF RFID chip via the diode D1 and the capacitor C3. When the RF energy signal is sent by the gateway and is a command signal, the UHF RFID chip starts to respond, collects sensor data, and reflects it through the UHF wireless channel. The gateway receives the tag identification data and sensor data transmitted by the tag, and a round of communication process is completed; When the voltage on the energy storage capacitor is lower than the set threshold, the control signal SW is at a low level of 0V, and the system returns to the energy collection state.

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