SE2030203A1

SE2030203A1 - Rf energy harvesting system

Info

Publication number: SE2030203A1
Application number: SE2030203A
Authority: SE
Inventors: Fangxin Jiang
Original assignee: Fangxin Jiang
Priority date: 2019-06-19
Filing date: 2020-06-19
Publication date: 2020-12-20

Abstract

An RF energy harvesting system (100) includes an antenna (10), an impedance matching network (20), an RF rectifier module (30), an enhanced RF rectifier module (40), a protection circuit (50), a power control module (60), an energy storage branch (70) and load branches (80). The antenna (10) receives RF signals and converts the RF signals into electric energy. The impedance matching network (20) produces an initial voltage signal according to the electric energy output by the antenna (10). The RF rectifier module (30) converts the initial voltage signal into a first voltage signal. The enhanced RF rectifier module (40) converts the initial voltage signal into a second voltage signal. The power control module (60) is self-driven through the first voltage signal and the second voltage signal. The RF rectifier module (30) adjusts the internal electrical connection according to control signals of the power control module (60). The energy storage branch (70) stores the electric energy output by the power control module (60).

Description

RF ENERGY HARVESTING SYSTEM Field of the Patent Application The present patent application generally relates to electronic technologies and more speciﬁcally to an RF energy harvesting system.

Background Converting energy harvested from the nature into electric energy without batteries or a Wiredpower supply is one of the developmental directions of power supply technology. RF energyharvesting technology can provide ﬂexible, portable and renewable energy resources andtherefore has become a research hotspot of the public. Conventional RF energy harvestingsystems typically include an antenna and an RF rectiﬁer. The antenna is conﬁgured to receiveRF signals and the rectiﬁer is conﬁgured to convert the received RF energy into a DC powersupply. However, the self-adaptability of such systems is not strong and the input energy isoften not stable while the energy output of a system is often required to be as stable as possibleand the output power is required to be high. Conventional RF energy harvesting systems oftenneed to be equipped with an extemal power source and cannot be self-driven. At the same time,redundant energy harvested by conventional RF energy harvesting systems can only be storedoutside the systems instead of being stored inside the systems, thus leading to inconveniencein operating and using such systems. On the other hand, the load of such systems often variesand the variation of load may inﬂuence the operation of such systems, and therefore does harrn to the stability of such systems.

Summary The present patent application is directed to an RF energy harvesting system. In one aspect,the present patent application provides an RF energy harvesting system. The RF energyharvesting systern includes an antenna configured to receive RF signals and convert energy ofthe RF signals to electric energy; an impedance matching network configured to optimizeconversion efficiency of the electric energy so as to produce an initial voltage signal; an RFrectiﬁer module configured to convert the initial voltage signal to a first voltage signal; anenhanced RF rectifier module configured to convert the initial voltage signal to a secondvoltage signal and voltage of the second voltage signal is greater than voltage of the firstvoltage signal; a power control module conﬁgured to power the power control module itselfthrough receiving the first voltage signal and the second voltage signal; an energy storagebranch and multiple load branches. The power control module is configured to transmit acontrol signal to the RF rectifier module so that the RF rectifier module adjusts electricalconnections between multiple rectiﬁers in the RF rectifier module, thus realizing maximumoutput of energy. The power control module is further configured to provide electric energyfor the energy storage branch and the load branches. The energy storage branch is configuredto store electric energy output by the power control module. The load branches are configured to be driven by the electric energy output by the power control module.

The multiple rectifiers in the RF rectifier module may be connected with one another throughlogic circuits so that multiple stages of rectifier units sequentially connected in series areformed. The RF rectifier module may vary the number of rectifiers connected in parallel in each rectifier unit according to the control signal.

When the initial voltage signal decreases, the RF rectifier module may reduce the number ofrectifiers connected in parallel in each rectifier unit so that the number of stages of the rectifierunits increases, thus ensuring that the first voltage signal remains constant. When the initialvoltage signal increases, the RF rectifier module may increase the number of rectifiersconnected in parallel in each rectifier unit, so that the number of stages of the rectifier units decreases, thus ensuring that the first voltage signal remains constant. 2 The rectifier unit may include one rectifier or at least two rectifiers connected in parallel witheach other. The rectifier may include an input port, an output port and a control port. The inputport of each rectifier may receive the initial Voltage signal. Control ports of all rectiﬁers in arectifier unit of a first stage may be connected to the ground. Control ports of all rectifiers ineach rectiﬁer unit except the rectifier unit of the first stage may be connected with output portsof all rectiﬁers in a neighboring rectifier unit of a previous stage. A total voltage output byoutput ports of all rectifiers in a rectifier unit of a last stage may be an output voltage of the RF rectifier module.

The power control module may include a rectification control unit and a load managementunit. The rectification control unit may be configured to transmit the control signal to the RFrectiﬁer module according to an estimate of the first voltage signal under an open circuitcondition. The load management unit including a logic control circuit may be configured to provide electric energy for the load branches and the energy storage branch.

The load management unit may be further configured to adjust duty ratio in real time so thatonly when a voltage provided for the load branches meets requirements, the electric energy may be transmitted to the load branches so as to protect the load branches.

The load management unit may include a first electronic switch, a second electronic switch, athird electronic switch, a first capacitor, a second capacitor and a resistor. The input port of thefirst electronic switch may be connected with the RF rectiﬁer module. The output port of thefirst electronic switch may be connected to the ground through the first capacitor andconnected to the ground through the second electronic switch and the second capacitor. Theinput port of the third electronic switch may be connected with the RF rectifier module whilethe output port of the third electronic switch may be connected to the ground through the resistor.

The power control module may further include a clock generating unit and a reference Voltagegenerating unit. The clock generating unit may be conﬁgured to produce clock signals for alldigital circuits in the RF energy harvesting system. The reference voltage generating unit maybe conﬁgured to produce reference voltage signals for all circuits in the RF energy harvesting system.

In another aspect, the present patent application provides an RF energy harvesting system. TheRF energy harvesting system includes an antenna configured to receive RF signals and convertenergy of the RF signals to electric energy; an impedance matching network configured tooptimize conversion efficiency of the electric energy so as to produce an initial voltage signal;an RF rectifier module configured to convert the initial voltage signal to a first voltage signal;an enhanced RF rectifier module configured to convert the initial voltage signal to a secondvoltage signal and voltage of the second voltage signal is greater than voltage of the firstvoltage signal; a power control module conﬁgured to power the power control module itselfthrough receiving the first voltage signal and the second voltage signal; an energy storage branch and multiple load branches.

The power control module includes a rectification control unit and a load management unit.The rectification control unit is configured to transmit a control signal to the RF rectifiermodule according to an estimate of the first voltage signal under an open circuit condition sothat the RF rectifier module adjusts electrical connections between multiple rectiﬁers in theRF rectiﬁer module, thus varying the number of rectifiers connected in parallel in each rectifierunit and realizing maximum output of energy. The load management unit is conﬁgured toprovide electric energy for the load branches and the energy storage branch and furtherconfigured to adjust duty ratio in real time so that only when a voltage provided for the loadbranches meets requirements, the electric energy is transmitted to the load branches so as toprotect the load branches. The energy storage branch is configured to store electric energyoutput by the load management unit. The load branches are configured to be driven by the electric energy output by the load management unit. 4 The load management unit may include a first electronic switch, a second electronic switch, athird electronic switch, a first capacitor, a second capacitor and a resistor. The input port of thefirst electronic switch may be connected with the RF rectifier module. The output port of thefirst electronic switch may be connected to the ground through the first capacitor andconnected to the ground through the second electronic switch and the second capacitor. Theinput port of the third electronic switch may be connected with the RF rectifier module and theoutput port of the third electronic switch may be connected to the ground through the resistor.The rectifier unit may include one rectifier or at least two rectifiers connected in parallel witheach other. The rectifier may include an input port, an output port and a control port. The inputport of each rectifier may receive the initial voltage signal. Control ports of all rectiﬁers in arectifier unit of a first stage may be connected to the ground. Control ports of all rectifiers ineach rectiﬁer unit except the rectifier unit of the first stage may be connected with output portsof all rectiﬁers in a neighboring rectifier unit of a previous stage. A total voltage output byoutput ports of all rectifiers in a rectifier unit of a last stage may be an output voltage of the RF rectifier module.

The RF energy harvesting system may further include a protection circuit. The protectioncircuit may be connected with the RF rectiﬁer module and the enhanced RF rectiﬁer moduleand configured to prevent the second voltage signal from being too high so as to ensure stability of the RF energy harvesting system.

Brief Description of the Drawings FIG. l is a block diagram of an RF energy harvesting system in accordance with an embodiment of the present patent application.

FIG. 2 is a schematic circuit diagram of one embodiment of an RF rectifier module of the RF energy harvesting system as depicted in FIG. 1.

FIG. 3 is a schematic Circuit diagram of one embodiment of an RF rectifier module of the RF energy harvesting system as depicted in FIG. 1.

FIG. 4 is a block diagram of a power control module of the RF energy harvesting system as depicted in FIG. 1.

FIG. 5 is a block diagram of a load management unit of the power control module as depicted in FIG. 4.

Detailed Description Reference will now be made in detail to a preferred embodiment of the RF energy harvestingsystem disclosed in the present patent application, examples of which are also provided in thefollowing description. Exemplary embodiments of the RF energy harvesting system disclosedin the present patent application are described in detail, although it will be apparent to thoseskilled in the relevant art that some features that are not particularly important to an understanding of the RF energy harvesting system may not be shown for the sake of clarity.

Furthermore, it should be understood that the RF energy harvesting system disclosed in thepresent patent application is not limited to the precise embodiments described below and thatVarious changes and modifications thereof may be effected by one skilled in the art withoutdeparting from the spirit or scope of the protection. For example, elements and/ or features ofdifferent illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure.

FIG. 1 is a block diagram of an RF energy harvesting system in accordance with anembodiment of the present patent application. Referring to FIG. 1, the RF energy harvesting system 100 includes an antenna 10, an impedance matching network 20, an RF rectifier module 6 , an enhanced RF rectifier module 40, a protection circuit 50, a power control module 60, an energy storage branch 70 and load branches 80.

The antenna 10 is conﬁgured to receive RF signals and convert RF energy into electric energy.In this embodiment, the antenna 10 is configured to receive the RF signals with a frequency of 950 to 1050 MHZ.

The impedance matching network 20 is configured to optimize the conversion efficiency of the electric energy so as to produce an initial voltage signal V0.

The RF rectifier module 30 is configured to convert the initial voltage signal V0 from an ACsignal to a DC signal so as to produce a first voltage signal VI . The RF rectiﬁer module 30 isfurther configured to automatically adjust the electrical connections between multiple rectifiers31 in the RF rectifier module 30 according to the input power (i.e. control signals transmittedby the power control module 60) so as to optimize the overall output efficiency of the RF energy harvesting system 100 and realize the maximum output of energy.

Referring to FIG. 2 and FIG. 3, the multiple rectiﬁers 31 in the RF rectif1er module 30 areconnected with one another through logic circuits (e.g. AND gate, NOT gate, OR gate, etc.)so that the electrical connections between the multiple rectiﬁers 31 is varied according to thereal-time variation of the input energy. As a result, multiple stages of rectiﬁer units 3lasequentially connected in series are formed and the number of rectiﬁers 31 connected inparallel in each rectifier unit 3 la can be varied so as to realize the maximum output of energy and stabilize the output power.

The rectiﬁer unit 3 la includes one rectifier 31 or at least two rectif1ers 31 connected in parallelwith each other. The rectifier 31 includes an input port 311, an output port 312 and a controlport 313. The input port 311 of each rectif1er 31 receives the initial voltage signal V0. Control ports 313 of all rectifiers 31 in a rectifier unit 3 la of a first stage are connected to the ground. 7 Control ports 313 of all rectifiers 31 in each rectifier unit 31a except the rectifier unit 31a ofthe first stage are connected with output ports 312 of all rectifiers 31 in a neighboring rectifierunit 31a of a previous stage. A total Voltage output by output ports 313 of all rectifiers 31 in arectiﬁer unit 31a of a last stage is an output Voltage of the RF rectifier module 30. In thisembodiment, the structures of the multiple rectiﬁer units 3 la are identical. Of course, in other embodiments, the structures of the multiple rectifier units 3 la may be different.

Referring to FIG. 2, when the initial Voltage signal V0 decreases, the RF rectifier module 30reduces the number of rectifiers 31 connected in parallel in each rectifier unit 3 la so that thenumber of stages of the rectifier units 3 la increases, thus ensuring that the first Voltage signalVI may not decrease with the decrease of the initial Voltage signal V0 and remains constant allthe time so as to increase the maximum output power. Speciﬁcally, for example, each rectifierunit 3 la includes one rectifier 31. If the number of the rectifiers 31 is M, rectifier units 3 la ofM stages are formed. Each rectifier unit 31a is configured to convert the initial Voltage signalV0 to a Voltage Vx+V0, then an output Voltage of the rectiﬁer unit 31a of the first stage isVx+ V0, an output Voltage of the rectifier unit 3 la of the second stage is 2Vx+ V0, and the like,an output Voltage of the rectiﬁer unit 3 la of the Mth stage is M Vx+ V0, and therefore the outputVoltage VI of the RF rectifier module 30 is MVx+V0.

Referring to FIG. 3, when the initial Voltage signal V0 increases, the RF rectiﬁer module 30increases the number of rectifiers 31 connected in parallel in each rectifier unit 3 la, so that thenumber of stages of the rectifier units 3 la decreases, thus ensuring that the first Voltage signalVI remains constant and the output current increases so as to increase the maximum outputpower. Specifically, at this time, each rectifier unit 31a includes at least two rectifiers 31connected in parallel with each other. In this embodiment, each rectifier unit 3 la includes tworectiﬁers 31 connected in parallel with each other. If the number of the rectifiers 31 is M,rectifier units 31a of M/2 stages are formed. Of course, the number of rectifiers 31 in eachrectiﬁer unit 3 la is not limited to this embodiment. Each rectifier unit 3 la is configured to convert the initial Voltage signal V0 to a Voltage Vx+ V0, then an output Voltage of the rectifier 8 unit 3la of the first stage is Vx+ V0, an output voltage of the rectiﬁer unit 3la of the secondstage is 2Vx+ V0 and the like, an output voltage of the rectiﬁer unit 3 la of the M/2th stage isMVx/2+V0, and therefore an output voltage VI of the RF rectifier module 30 is MVx/2+V0.

The enhanced RF rectifier module 40 is configured to convert the initial Voltage signal V0 froman AC signal to a DC signal so as to produce a second voltage signal V2 and the voltage of the second voltage signal V2 is greater than the voltage of the first voltage signal VI .

The protection circuit 50 is connected with the RF rectifier module 30 and the enhanced RFrectifier module 40 and configured to prevent the second voltage signal V2 from being too high so as to ensure the stability of the RF energy harvesting system 100.

The power control module 60 is configured to power the power control module 60 itselfthrough receiving the first voltage signal VI and the second voltage signal V2 so as to realize self-driving of the RF energy harvesting system l00 without an extemal power supply.

The power control module 60 is further conﬁgured to provide clock signals and referencevoltage signals for the RF energy harvesting system l00, provide control signals for the RFrectifier module 30 and provide electric energy for the energy storage branch 70 and the loadbranches 80. Referring to FIG. 4, the power control module 60 includes a clock generating unit6l, a reference voltage generating unit 62, a rectification control unit 63 and a load management unit 64.

The clock generating unit 6l is configured to produce the clock signals for all digital circuits in the RF energy harvesting system 100.

The reference voltage generating unit 62 is configured to produce the reference voltage signalsfor all circuits in the RF energy harvesting system l00. The reference voltage signals vary little with temperature and processing while remaining essentially constant. 9 The rectification control unit 63 is configured to transmit the control signals to the RF rectiﬁermodule 30 according to an estimate of the first Voltage signal VI under an open circuitcondition so that the RF rectifier module 30 can configure the electrical connections between the multiple rectiﬁers 3l in the RF rectifier module 30 according to the control signals.

The load management unit 64 including a logic control circuit is configured to provide electricenergy for the energy storage branch 70 and the load branches 80. The load management unit64 is further configured to adjust the duty ratio in real time so that the electric energy istransmitted to the load branches 80 only when the voltage provided for the load branches 80meets requirements, thus realizing the protection of the load branches 80. At the same time,the redundant energy is stored in a capacitor for energy storage. In addition, the loadmanagement unit 64 can adjust the energy output in real time according to the variation of theload branches 80 so as to realize real-time load management and improve the system”scapability of adapting to different application scenarios. Referring to FIG. 5, the loadmanagement unit 64 includes a first electronic switch 641, a second electronic switch 642, a third electronic switch 643, a first capacitor 644, a second capacitor 645 and a resistor 646.

The input port of the first electronic switch 64l is connected with the RF rectifier module 30.The output port of the first electronic switch 64l is connected to the ground through the firstcapacitor 644 and connected to the ground through the second electronic switch 642 and thesecond capacitor 645. The input port of the third electronic switch 643 is connected with theRF rectifier module 30 while the output port of the third electronic switch 643 is connected tothe ground through the resistor 646. The intemal resistance of the RF rectiﬁer module 30 is R0 and the resistance of the resistor 646 is RI.

The operating process of the load management unit 64 is as follows: when energy from the RFrectifier module 30 is less than the requirements of the load branches 80, R0>RI and adjusting the third electronic switch 643 so as to lower the duty ratio; when energy from the RF rectifier module 30 is greater than the requirements of the load branches 80, R0 644 charges the second capacitor 645.

The energy storage branch 70 is conﬁgured to store the electric energy output by the power control module 60.

The load branches 80 are conﬁgured to be driven by the electric energy output by the power control module 60.

Compared with the conventional RF energy harvesting systems, in the RF energy harvestingsystem 100 of the present patent application, the RF rectifier module 30 can vary the numberof rectifiers 3l connected in parallel in each rectifier unit 3la according to the real-timevariation of input energy so as to realize the maximum output of energy and stable outputpower and strong self-adaptability. Since the first voltage signal produced by the RF rectifiermodule 30 and the second voltage signal produced by the enhanced RF rectifier module 40can power the power control module 60 directly, the RF energy harvesting system can be self-driven without an extemal power supply. Since the load management unit 64 can not onlycontrol and store the redundant energy, but also adjust the energy output in real time accordingto the variation of the load branches, the RF energy harvesting system is convenient to operatewith strong stability and can be applied to a wide range of application scenarios. At the sametime, since all modules in the RF energy harvesting system l00 are integrated on a chip, theintegration of the RF energy harvesting system l00 is high and therefore the cost is further lowered. 11 While the present patent application has been shown and described With particular referencesto a number of ernbodirnents thereof, it should be noted that Various other changes or rnodiﬁcations may be rnade Without departing from the scope of the present inVention. 12

Claims

What is claimed is:

1. An RF energy harvesting system (100) comprising: an antenna (10) configured to receive RF signals and convert energy of the RF signals toelectric energy; an impedance matching network (20) configured to optimize conversion efficiency of theelectric energy so as to produce an initial voltage signal; an RF rectifier module (30) configured to convert the initial voltage signal to a ﬁrst voltagesignal; an enhanced RF rectifier module (40) configured to convert the initial voltage signal to asecond voltage signal and voltage of the second voltage signal is greater than voltage of thefirst voltage signal; a power control module (60) configured to power the power control module (60) itself throughreceiving the first voltage signal and the second voltage signal; an energy storage branch (70); and a plurality of load branches (80); wherein: the power control module (60) is conﬁgured to transmit a control signal to the RF rectiﬁermodule (30) so that the RF rectiﬁer module (30) adjusts electrical connections between aplurality of rectifiers (31) in the RF rectifier module (3 0), thus realizing maximum output ofenergy; the power control module (60) is further conﬁgured to provide electric energy for the energystorage branch (70) and the load branches (80); the energy storage branch (70) is conﬁgured to store electric energy output by the powercontrol module (60); and the load branches (80) are conﬁgured to be driven by the electric energy output by the power control module (60).

2. The RF energy harvesting system (100) of claim 1, wherein the plurality of rectifiers (31) in the RF rectiﬁer module (30) are connected with one another through logic circuits so that 13 multiple stages of rectifier units (31a) sequentially connected in series are formed; the RFrectifier module (30) can Vary the number of rectifiers (31) connected in parallel in each rectiﬁer unit (3 1 a) according to the control signal.

3. The RF energy harvesting system (100) of claim 2, Wherein When the initial Voltage signaldecreases, the RF rectifier module (30) reduces the number of rectifiers (31) connected inparallel in each rectifier unit (31a) so that the number of stages of the rectiﬁer units (31a)increases, thus ensuring that the first Voltage signal remains constant; When the initial Voltagesignal increases, the RF rectifier module (30) increases the number of rectiﬁers (31) connectedin parallel in each rectifier unit (31a), so that the number of stages of the rectifier units (31a) decreases, thus ensuring that the first Voltage signal remains constant.

4. The RF energy harvesting system (100) of claim 3, Wherein the rectifier unit (3 1 a) comprisesone rectifier (31) or at least two rectifiers (31) connected in parallel With each other; therectifier (31) comprises an input port (311), an output port (312) and a control port (313); theinput port (311) of each rectiﬁer (31) receives the initial Voltage signal; control ports (313) ofall rectifiers (31) in a rectifier unit (31a) of a first stage are connected to the ground; controlports (313) of all rectiﬁers (31) in each rectifier unit (31a) except the rectifier unit (31a) of thefirst stage are connected With output ports (312) of all rectifiers (31) in a neighboring rectifierunit (31a) of a previous stage; a total Voltage output by output ports (313) of all rectiﬁers (31)in a rectifier unit (31a) of a last stage is an output Voltage of the RF rectifier module (30).

5. The RF energy harvesting system (100) of claim 4, Wherein the power control module (60)comprises a rectification control unit (63) and a load management unit (64); the rectificationcontrol unit (63) is conﬁgured to transmit the control signal to the RF rectifier module (30)according to an estimate of the first Voltage signal under an open circuit condition; the loadmanagement unit (64) comprising a logic control circuit is configured to provide electricenergy for the load branches (80) and the energy storage branch (70); the load management unit (64) is further configured to adjust duty ratio in real time so that only When a Voltage 14 provided for the load branches (80) meets requirements, the electric energy is transmitted to the load branches (80) so as to protect the load branches (80).

6. The RF energy harvesting system (100) of claim 5, wherein the load management unit (64)comprises a first electronic switch (64l), a second electronic switch (642), a third electronicswitch (643), a first capacitor (644), a second capacitor (645) and a resistor (646); the inputport of the first electronic switch (64l) is connected with the RF rectifier module (30); theoutput port of the ﬁrst electronic switch (64l) is connected to the ground through the firstcapacitor (644) and connected to the ground through the second electronic switch (642) andthe second capacitor (645); the input port of the third electronic switch (643) is connected withthe RF rectifier module (30) while the output port of the third electronic switch (643) is connected to the ground through the resistor (646).

7. The RF energy harvesting system (l00) of claim l, wherein the power control module (60)further comprises a clock generating unit (6 l) and a reference Voltage generating unit (62); theclock generating unit (6l) is configured to produce clock signals for all digital circuits in theRF energy harvesting system (l00); the reference Voltage generating unit (62) is conﬁgured to produce reference Voltage signals for all circuits in the RF energy harvesting system (l 00).

8. An RF energy harvesting system (l00) comprising: an antenna (l0) configured to receive RF signals and convert energy of the RF signals toelectric energy; an impedance matching network (20) configured to optimize conversion efficiency of theelectric energy so as to produce an initial Voltage signal; an RF rectifier module (30) configured to convert the initial Voltage signal to a first Voltagesignal; an enhanced RF rectifier module (40) configured to convert the initial Voltage signal to asecond Voltage signal and Voltage of the second Voltage signal is greater than Voltage of the first Voltage signal; a power control module (60) configured to power the power control module (60) itself throughreceiving the first voltage signal and the second voltage signal; an energy storage branch (70); and a plurality of load branches (80); wherein: the power control module (60) comprises a rectification control unit (63) and a loadmanagement unit (64); the rectification control unit (63) is configured to transmit a control signal to the RF rectifiermodule (3 0) according to an estimate of the first voltage signal under an open circuit conditionso that the RF rectifier module (3 0) adjusts electrical connections between a plurality ofrectiﬁers (3l) in the RF rectifier module (30), thus varying the number of rectifiers (3l)connected in parallel in each rectiﬁer unit (3 la) and realizing maximum output of energy; the load management unit (64) is configured to provide electric energy for the load branches(80) and the energy storage branch (70) and further configured to adjust duty ratio in real timeso that only when a voltage provided for the load branches (80) meets requirements, the electricenergy is transmitted to the load branches (80) so as to protect the load branches (80); the energy storage branch (70) is configured to store electric energy output by the loadmanagement unit (64); and the load branches (80) are conﬁgured to be driven by the electric energy output by the load management unit (64).

9. The RF energy harvesting system (l00) of claim 8, wherein the load management unit (64)comprises a first electronic switch (641), a second electronic switch (642), a third electronicswitch (643), a first capacitor (644), a second capacitor (645) and a resistor (646); the inputport of the first electronic switch (64l) is connected with the RF rectifier module (30); theoutput port of the first electronic switch (64l) is connected to the ground through the firstcapacitor (644) and connected to the ground through the second electronic switch (642) andthe second capacitor (645); the input port of the third electronic switch (643) is connected withthe RF rectifier module (30) while the output port of the third electronic switch (643) is connected to the ground through the resistor (646); the rectifier unit (3la) comprises one 16 rectifier (31) or at least two rectifiers (31) connected in parallel With each other; the rectifier(31) comprises an input port (311), an output port (312) and a control port (313); the input port(31 1) of each rectif1er(31) receives the initial Voltage signal; control ports (313) of all rectifiers(31) in a rectifier unit (31a) of a first stage are connected to the ground; control ports (313) ofall rectifiers (31) in each rectiﬁer unit (31a) except the rectiﬁer unit (31a) of the first stage areconnected With output ports (312) of all rectifiers (31) in a neighboring rectiﬁer unit (31a) ofa previous stage; a total Voltage output by output ports (313) of all rectifiers (31) in a rectiﬁerunit (31a) of a last stage is an output Voltage of the RF rectif1er module (30).

10. The RF energy harvesting system (100) of claim 9 further comprising a protection circuit(50), Wherein the protection circuit (5 0) is connected With the RF rectifier module (3 0) and theenhanced RF rectifier module (40) and configured to prevent the second Voltage signal from being too high so as to ensure stability of the RF energy harvesting system (100). 17