CN117220424A

CN117220424A - Passive RFID circuit based on 2.4GHz frequency band

Info

Publication number: CN117220424A
Application number: CN202310969955.7A
Authority: CN
Inventors: 虞洋华
Original assignee: Jiangsu Huarui Technology Co ltd
Current assignee: Jiangsu Huarui Technology Co ltd
Priority date: 2023-08-02
Filing date: 2023-08-02
Publication date: 2023-12-12

Abstract

The application provides a passive RFID circuit based on a 2.4GHz frequency band, which comprises an energy receiving antenna for receiving space electromagnetic wave energy, wherein the output end of the energy receiving antenna is electrically connected with a rectifying voltage doubling module adopting a Schottky diode; the output end of the rectifying voltage doubling module is electrically connected with the power management module, and the output end of the power management module is electrically connected with the 2.4GHz RFID antenna module on one hand and the energy storage module on the other hand. The conduction threshold of the rectifying voltage doubling module is reduced by using the diode with the Schottky diode, so that the boosting amplitude of the rectifying voltage doubling module is improved, and the utilization rate of space electromagnetic wave energy is improved.

Description

Passive RFID circuit based on 2.4GHz frequency band

Technical Field

The application relates to the field of wireless charging, in particular to a passive RFID circuit based on a 2.4GHz frequency band.

Background

Radio frequency identification (Radio Frequency Identification, RFID) is a currently commonly used automatic identification technology, and communication is established between a reader-writer and an electronic tag through wireless signals, so that contactless information transmission is realized.

The existing RFID can be divided into an active RFID and a passive RFID according to different power supply modes, wherein the active RFID is powered by built-in components such as a battery and the like, and the existing RFID has the defects of large volume and high cost; the latter converts the electromagnetic wave in the acquired space into electric energy, but has the defects of short communication distance and poor recognition stability.

In order to solve the defects of the two modes, a technical scheme for adopting space energy collection to supply energy is proposed in the prior art. Although the problem of energy source is solved, the output boosting range is only about 100mV, which means that the electromagnetic wave energy under the same antenna needs to be about 10dB higher than the design, and the defect of low energy utilization rate exists.

Disclosure of Invention

Based on the above, it is necessary to provide a passive RFID circuit based on the 2.4GHz band, which reduces the turn-on threshold of the rectifying voltage-multiplying module by using a schottky diode, thereby increasing the boost amplitude of the rectifying voltage-multiplying module and increasing the utilization rate of the space electromagnetic wave energy.

In a first aspect, the present application provides a passive RFID circuit based on the 2.4GHz band, the passive RFID circuit comprising:

the energy receiving antenna is used for receiving space electromagnetic wave energy, and the output end of the energy receiving antenna is electrically connected with the rectifying voltage doubling module adopting the Schottky diode;

the output end of the rectifying voltage doubling module is electrically connected with the power management module, and the output end of the power management module is electrically connected with the 2.4GHz RFID antenna module on one hand and the energy storage module on the other hand.

In one embodiment, the energy receiving antenna is disposed at an edge position of the passive RFID circuit

In one embodiment, the energy receiving antenna comprises a planar inverted-F antenna.

In one embodiment, the rectification voltage doubling module comprises:

a signal source for receiving the output signal of the energy receiving antenna, and a rectifying and multiplying loop;

the signal source is provided with a positive end and a negative end, and the rectifying and multiplying loop is arranged between the positive end and the negative end;

the rectification multiplication loop comprises a capacitor and a Schottky diode electrically connected with the capacitor.

In one embodiment, the rectification multiplication circuit includes:

a primary rectifying and multiplying circuit connected in series by a capacitor C1 and a Schottky diode D1;

two ends of the Schottky diode D1 are connected in parallel with a secondary rectifying and multiplying loop which is formed by connecting a capacitor C2 and the Schottky diode D2 in series.

In one embodiment, the rectification multiplication circuit includes:

a primary rectifying and multiplying circuit connected in series by a capacitor C1 and a Schottky diode D1, and a secondary rectifying and multiplying circuit connected in series by a capacitor C2 and a Schottky diode D2 are connected in parallel at two ends of the Schottky diode D1;

the three-stage rectification multiplication circuit formed by connecting a capacitor C3, a Schottky diode D3 and a capacitor C2 in series is connected with four-stage rectification multiplication circuits formed by connecting a Schottky diode D4 and a capacitor C4 in series in parallel at two ends of a circuit formed by connecting the Schottky diode D1 and the capacitor C2 in series;

the capacitor C5 and the Schottky diode D6 are connected in series with a five-stage rectifying and multiplying circuit, and six-stage rectifying and multiplying circuits formed by the Schottky diode D5 and the capacitor C6 which are connected in series are connected in parallel at two ends of a circuit formed by the Schottky diode D6 and the capacitor C4 which are connected in series.

In one embodiment, the rectifying and multiplying circuit has a boost range of 30mV to 1.8V.

In one embodiment, the 2.4GHz RFID antenna module comprises:

the system comprises a 2.4GHz RFID active module electrically connected with the output end of the power management module and a 2.4GHz RFID antenna electrically connected with the output end of the 2.4GHz RFID active module.

In one embodiment, the 2.4GHz RFID antenna adopts a PCB microstrip antenna structure.

In one embodiment, an impedance matching module is further provided between the energy receiving antenna and the rectifying voltage doubler module.

According to the passive RFID circuit in the 2.4GHz frequency band, the conduction threshold of the rectifying voltage doubling module is reduced by using the Schottky diode, so that the boosting amplitude of the rectifying voltage doubling module is improved, and the utilization rate of space electromagnetic wave energy is improved.

Drawings

FIG. 1 is a schematic diagram of a passive RFID circuit based on the 2.4GHz band in one embodiment;

fig. 2 is a schematic diagram of S11 simulation values of a PIFA antenna in one embodiment;

FIG. 3 is a schematic diagram of a double-pass rectification multiplication circuit according to another embodiment;

FIG. 4 is a schematic diagram of a six-pass rectifying and multiplying circuit according to another embodiment;

FIG. 5 is a schematic diagram of a 2.4GHz RFID antenna in one embodiment;

FIG. 6 is a schematic diagram of S11 simulation values of a 2.4GHz RFID antenna in one embodiment.

Detailed Description

The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.

The terminal 102 may be, but not limited to, various personal computers, notebook computers, smart phones, tablet computers, internet of things devices, and portable wearable devices, and the internet of things devices may be smart speakers, smart televisions, smart air conditioners, smart vehicle devices, and the like. The portable wearable device may be a smart watch, smart bracelet, headset, or the like. The server 104 may be implemented as a stand-alone server or as a server cluster of multiple servers.

In one embodiment, as shown in fig. 1, a passive RFID circuit 10 based on a 2.4GHz band according to an embodiment of the present application includes:

an energy receiving antenna 11 for receiving electromagnetic wave energy in space, wherein the output end of the energy receiving antenna 11 is electrically connected with a rectifying voltage doubling module 13 adopting a Schottky diode;

the output end of the rectifying voltage doubling module 13 is electrically connected with the power management module 15, and the output end of the power management module 15 is electrically connected with the 2.4GHz RFID antenna module 17 on one hand and the energy storage module 19 on the other hand.

In practice, the main structure of the passive RFID circuit includes five parts, namely an energy receiving antenna 11, a rectifying voltage doubler module 13, a power management module 15, a 2.4GHz RFID antenna module 17 and an energy storage module 19.

Specifically, the energy receiving antenna 11 collects electromagnetic wave energy in a space where the passive RFID circuit is located by receiving electromagnetic wave signals, and then transmits the received electromagnetic wave signals to the rectifying and voltage multiplying module 13 for realizing conversion from AC to DC and multiplication and amplification of voltage. The multiplied and amplified voltage is input to the power management module 15 to realize the voltage stabilizing output of 3.3V. The electric energy output by the voltage stabilization is transmitted to the energy storage module 19 for storage on the one hand to the 2.4GHz RFID antenna module 17 and on the other hand.

In the processing process, the Schottky diode is used for replacing a common diode in the arrangement voltage doubling module, and the Schottky diode is extremely low in conduction threshold value, so that higher energy conversion efficiency is brought, the energy utilization rate of electromagnetic waves is further improved, and a larger boosting range is provided.

In one embodiment, the energy receiving antenna 11 is disposed at an edge location of the passive RFID circuit. The energy receiving antenna 11 comprises a planar inverted-F antenna.

In practice, the energy receiving antenna 11 is mainly used for collecting electromagnetic waves in space, so the energy receiving antenna 11 herein often needs to have a broadband and high gain characteristic.

It should be noted here that, only the bandwidth of the front-end energy receiving antenna needs to be extended to collect more description of spatial energy, the specific principle is that: the bandwidth of the antenna is represented by the S11 parameter, as shown in FIG. 3, the engineering application is measured by-10 dB, when S11 is < -10dB, 90% of energy can be converted, the design mainly aims at energy near 2.4GHz, but GSM,5G, wifi-5.8GHz and the like are also adopted in the real space, and if the bandwidth of the front-end antenna design is below-10 dB in the frequency bands S11, more space energy can be collected and stored.

In addition, in order to promote the energy collection system to receive energy in each radiation area, in this embodiment, a Planar Inverted F Antenna (PIFA) is respectively disposed at the peripheral edge of the circuit board of the passive RFID circuit.

The PIFA antenna has the antenna size of 19 x 10 x 4mm, the corresponding S11 simulation value is shown in figure 2, and the 10dB bandwidth of 2.3-2.6 GHz covers the whole 2.4GHz free frequency band, so that all electromagnetic wave signals in the frequency band can be well received. Since 2.4GHz is a free frequency band, there are many technologies such as bluetooth, zigbee, wifi, wireless USB, etc. in this frequency band. The PIFA antenna structure is adopted in the antenna design, the antenna has good stability and strong anti-interference energy, and the maximum advantage only occupies small circuit board space, so that the miniaturization design can be satisfied.

The basic structure of a PIFA antenna comprises four partial ground planes, a radiating element, a shorting metal plate and a coaxial feed, the typical structure of which is shown in the following figures. The ground plane can be used as a reflecting surface, the radiating element is a metal sheet parallel to the ground plane, the short-circuit metal sheet is used for connecting the radiating element and the ground plane, and the coaxial feeder is used for signal transmission.

In one aspect, a PIFA antenna may be considered as being a derivative of a linear inverted-F antenna (i.e., an IFA antenna). For the IFA antenna, the radiating element and the ground wire are both thin conductor wires, so that the equivalent radio frequency distribution inductance is larger, and the distribution capacitance is smaller, which means that the antenna has a higher Q value and a narrower frequency band. According to the relation between the Q value and the bandwidth of the electrically small antenna, the bandwidth is increased by reducing the Q value, so that the thin wire of the IFA antenna is replaced by a metal sheet with a certain width, the distributed capacitance can be increased, the distributed inductance can be reduced, the bandwidth of the antenna can be increased, and the PIFA antenna can be formed. On the other hand, a PIFA antenna can also be considered as a rectangular microstrip antenna with a short circuit connection, the actual resonance mode of which is the same as that of the rectangular microstrip antenna, and which is resonant in TM10 mode. When the short-circuit metal sheet is arranged on the rectangular radiating metal sheet and the ground plane, the length of the rectangular radiating metal sheet can be halved, the purpose of reducing the size of the antenna is achieved, and the electric field of the TM10 mode at the position of the short-circuit metal sheet is equal to zero. When the width of the short circuit metal sheet is narrower than that of the radiation metal sheet, the effective inductance of the antenna is increased, and the resonance frequency is lower than that of the traditional short circuit rectangular microstrip antenna, so that the width of the short circuit metal sheet is reduced, and the size of the PIFA antenna can be further reduced.

In one embodiment, the rectifying voltage doubler module 13 includes:

a signal source for receiving the signal output from the energy receiving antenna 11, and a rectification multiplication circuit;

the signal source is provided with a positive end and a negative end, and the rectifying and multiplying loop is arranged between the positive end and the negative end; the rectification multiplication loop comprises a capacitor and a Schottky diode electrically connected with the capacitor.

In practice, the rectifying and voltage multiplying module 13 for converting electromagnetic waves into electric energy and amplifying the same comprises a signal source for receiving the output signal of the energy antenna and a rectifying and voltage-increasing rectifying and multiplying circuit.

The effect of rectification converts an AC signal to a DC signal, and because the radio frequency input energy is small, direct power cannot be supplied after rectification, and therefore multiplication amplification is required after rectification. The more sophisticated technique in rectifying voltage doubler module 13 uses capacitors and diodes, with conventional PN junction diodes typically having a turn-on threshold of 0.7V, with higher turn-on thresholds implying lower energy conversion. Considering the overall conversion efficiency, this embodiment employs schottky diodes of the SMS7621 series, which have extremely low turn-on thresholds of about 0.06V.

Specifically, a rectifying and multiplying circuit is connected between the positive terminal and the negative terminal of the signal source, and the basic structure of the rectifying and multiplying circuit comprises a capacitor and a schottky diode electrically connected with the capacitor.

In order to realize the rectification increasing processing of different steps, two detailed structures of rectification voltage doubling circuits are proposed:

as shown in fig. 3, the double-pass rectification multiplication circuit includes:

In practice, the double-pass rectification multiplication circuit is shown in fig. 4, and the principle is as follows: the radio frequency signal negative half cycle, the Schottky diode D1 is conducted, the Schottky diode D2 is cut off, current charges the capacitor C1 through the Schottky diode D1, the radio frequency signal positive half cycle, the Schottky diode D2 is conducted, the capacitor D1 is cut off, at the moment, the voltage on the capacitor C1 is added with the power supply voltage, the current flows through the Schottky diode D2 to charge the capacitor C2, the charging voltage is 2 x (V1-Vf), and Vf is the conduction threshold of the Schottky diode.

As shown in fig. 4, the six-pass rectification multiplier circuit includes:

It should be noted that, by using electromagnetic wave energy of 2.4GHz in the room, the antenna port collects power in the range of-30 to 10dBm, and adopts voltage doubling of 6 times of the range, and the corresponding output voltage from-30 dBm to 0dBm is 30mV to 1.8V.

The specific calculation process is as follows: the 30 mV-1.8V output is obtained through simulation by simulation software.

The corresponding effective voltage of 30 dBm-0 dBm under 50 ohm impedance is 7 mV-220 mV, the N-time range outputs 2N (V1-Vf), the Vf conduction threshold is 60mV, if V1 is larger than Vf, such as 220mV, 6 times range is equal to 2*6 (220-60) =1920 mV, when V1 is smaller than Vf, the capacitor is charged in the first stage until the conduction condition is reached, the process involves integration of the capacitor over time, and the integration is obtained by simulation software.

The working principle of the six-way rectifying and multiplying circuit is identical to that of the two-way rectifying and multiplying circuit, and the description is omitted here.

In one embodiment, a power management module 15 for performing voltage stabilization output is connected to the output end of the rectification voltage doubling module 13.

Typically, to meet the voltage requirements, the design uses LTC3108, which is an ultra-low voltage boost converter and power manager, whose boost architecture can operate at an input voltage as low as 20mV, and VOUT remains at an output of about 3.3V at an input voltage of 30 mV-1.8V after voltage doubling. The power supply voltage of the 2.4GHz RFID module is 3.3V and meets the requirement of load voltage.

After the voltage stabilization treatment is completed, the output end of the power management module 15 is simultaneously connected with the 2.4GHz RFID antenna module 17 and the energy storage module 19, so that the power is conveniently supplied to the power management module, the power management module can store energy by the power management module, and when the external electromagnetic wave energy is insufficient, electricity can be taken from the energy storage module 19 to meet the normal work of the passive RFID circuit.

In one embodiment, the 2.4GHz RFID antenna module 17 comprises:

the power management module 15 comprises a 2.4GHz RFID active module electrically connected with the output end of the power management module 15 and a 2.4GHz RFID antenna electrically connected with the output end of the 2.4GHz RFID active module.

In practice, 2.4GHz RFID modules and antenna technology are very mature and will not be described in any great detail herein. At present, the 2.4GHz RFID module basically adopts a single-chip implementation scheme, and the design adopts a Tab micro TLSR8359 to realize an active module design. The 2.4GHz RFID antenna adopts a PCB microstrip structure, a simulation model is shown in figure 5, and the grid lines are background wire frames in simulation software. The working frequency of the active RFID is 2.4-2.5 GHz, and the S11 parameter simulation result shown in FIG. 6 shows that the resonant frequency of the antenna is 2.45Ghz, so that the design selects 2.45GHz as an actual use frequency point.

The aforementioned energy storage module 19 is equipped with the energy storage module 19 in view of the fact that the energy collected by the environment is often less stable and varies with time. In general, two types of energy storage are adopted, one is a battery, the other is a super capacitor, the super capacitor is selected for energy storage in order to adapt to more environments, and the AVX Best Cap pulse super capacitor is selected, wherein the temperature range is-20-70 ℃.

In one embodiment, an impedance matching module is further provided between the energy receiving antenna 11 and the rectifying voltage doubler module 13.

In implementation, the impedance matching module is used for realizing the maximization of energy transmission between the receiving antenna and the rectifier diode, and improving the overall conversion efficiency. The matching can be realized through high-frequency inductance and capacitance, and the technology is mature and is not explained in detail.

It should be understood that, although the steps in the flowcharts related to the embodiments described above are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.

Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, database, or other medium used in embodiments provided herein may include at least one of non-volatile and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high density embedded nonvolatile Memory, resistive random access Memory (ReRAM), magnetic random access Memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric Memory (Ferroelectric Random Access Memory, FRAM), phase change Memory (Phase Change Memory, PCM), graphene Memory, and the like. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration, and not limitation, RAM can be in the form of a variety of forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), and the like. The databases referred to in the embodiments provided herein may include at least one of a relational database and a non-relational database. The non-relational database may include, but is not limited to, a blockchain-based distributed database, and the like. The processor referred to in the embodiments provided in the present application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, or the like, but is not limited thereto.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.

Claims

1. A passive RFID circuit based on the 2.4GHz band, the passive RFID circuit comprising:

2. The passive RFID circuit based on the 2.4GHz band of claim 1, wherein the energy receiving antenna is disposed at an edge location of the passive RFID circuit.

3. The passive RFID circuit based on the 2.4GHz band of claim 2, wherein the energy receiving antenna comprises a planar inverted-F antenna.

4. The passive RFID circuit based on the 2.4GHz band of claim 1, wherein the rectifying voltage doubler module comprises:

5. The passive RFID circuit based on the 2.4GHz band of claim 4, wherein the rectification multiplier circuit comprises:

6. The passive RFID circuit based on the 2.4GHz band of claim 4, wherein the rectification multiplier circuit comprises:

7. The passive RFID circuit based on the 2.4GHz band of claim 6, wherein the rectifying and multiplying loop has a boost range of 30mV to 1.8V.

8. The 2.4GHz band-based passive RFID circuit of claim 1, wherein the 2.4GHz RFID antenna module comprises:

9. The passive RFID circuit based on the 2.4GHz band of claim 8, wherein the 2.4GHz RFID antenna employs a PCB microstrip antenna structure.

10. A passive RFID circuit based on the 2.4GHz band as claimed in any one of claims 1 to 9, wherein,

and an impedance matching module is further arranged between the energy receiving antenna and the rectifying voltage doubling module.