CN118100469A - 2.45GHz rail transit precise positioning system beacon wake-up circuit and device - Google Patents

Abstract

The invention discloses a wake-up circuit and device of a beacon of a 2.45GHz track traffic accurate positioning system, and belongs to the field of wireless communication of track traffic. The circuit comprises: the antenna is electrically connected with the total input end of the three-stage voltage-doubling rectifying circuit through the impedance matching circuit; the total output end of the three-stage voltage doubling rectifying circuit is electrically connected with one input end of the comparator circuit; the other input end of the comparator circuit is a comparison voltage input end; the output of the comparator circuit is a beacon wakeup output. According to the invention, by adopting the three-stage voltage doubling rectifying circuit and utilizing the three-stage voltage doubling rectifying function, the input voltage is doubled, the power utilization efficiency is effectively improved, and enough energy can be effectively collected in a 2.45GHz high-frequency band with more signal attenuation, so that a beacon is quickly awakened. The wake-up circuit can ensure that the beacon has enough power supply when in wake-up while maintaining low power consumption, and meets the requirement of the beacon in a track traffic accurate positioning system with the frequency band of 2.45 GHz.

Description

2.45GHz rail transit precise positioning system beacon wake-up circuit and device

Technical Field

The present invention relates to the field of wireless communications for rail transit, and in particular to a wake-up circuit and device for a beacon of a 2.45 GHz rail transit precise positioning system.

Background technique

The rail transit system is an advanced transportation system that operates through a rail network, usually including trains, communication-based train control systems (CBCT) and other technical elements. The train automatic control system uses advanced communication technology to achieve automatic control of trains, thereby improving operational efficiency and safety. In the rail transit precise positioning system based on RFID technology, as shown in Figure 1, the reader is used to identify the beacon fixed on the trackside or on the sleeper, and the exact position of the train along the line is determined by the installation location of the beacon and the passing time of the train, which makes the train automatic control system to control the movement of the train safer and more reliable.

Beacons are industrial-grade RFID electronic tags that operate in the 2.45GHz frequency band. They can be used in urban rail transit, urban rail, and national railways. In urban rail transit systems, such as subways and light rails, which have a large number of vehicles and passenger flows, these beacons play a key role in real-time tracking of vehicle locations and monitoring of vehicle operations, thereby ensuring the safety and efficiency of vehicle operations. Through the precise location data provided by the beacons, the monitoring center can promptly understand the operating status of the vehicle and respond quickly to emergencies, further improving the punctuality and reliability of transportation.

In existing rail transit systems, beacons are usually designed to work continuously, that is, they remain active at all times. This working mode is accompanied by higher power consumption, resulting in a shorter life of the beacon. Therefore, it is necessary to explore new designs that use low-power wake-up technology to optimize energy consumption and extend the life of the beacon. With the development of low-power technology, most of the existing low-power MCUs include working state and sleep state, and the power consumption of the MCU in the sleep state is extremely low. Beacons in rail transit systems can benefit from this low-power wake-up technology, which allows devices to run with extremely low power consumption in a dormant state and wake up quickly and effectively when needed. This is critical to improving system efficiency and extending the life of beacons.

At present, in the design of passive RF wake-up circuits in the 900MHz frequency band, voltage doubling rectifier circuits are mostly used, mainly because the signal attenuation is relatively small in this frequency band, so it can more effectively collect energy for beacon wake-up. Compared with the 900MHz frequency band, the 2.45GHz high-frequency band has greater signal attenuation and more significant mutual inductance and capacitance effects between circuit components, which requires the circuit layout to be more precise to reduce signal transmission delay and loss. The existing passive RF wake-up circuits for the 900MHz frequency band cannot effectively collect energy in a short enough time to wake up the beacon, and the component selection of the 900MHz frequency band cannot meet the requirements of the 2.45GHz high-frequency environment. Therefore, how to provide a wake-up circuit that can effectively wake up the beacon in the 2.45GHz high-frequency band is a problem that needs to be solved.

In view of this, the present invention is proposed.

Summary of the invention

The purpose of the present invention is to provide a wake-up circuit and device for a 2.45GHz rail transit precise positioning system beacon, which can collect sufficient energy in the 2.45GHz high frequency band to realize the wake-up of the beacon, thereby solving the above-mentioned technical problems existing in the prior art.

The objective of the present invention is achieved through the following technical solutions:

A wake-up circuit for a 2.45GHz rail transit precise positioning system beacon, comprising:

Antenna, impedance matching circuit, three-stage voltage doubler rectifier circuit and comparator circuit; wherein,

The antenna is electrically connected to the total input end of the three-stage voltage doubler rectifier circuit via the impedance matching circuit;

The total output end of the three-stage voltage doubler rectifier circuit is electrically connected to an input end of the comparator circuit;

Another input terminal of the comparator circuit is a comparison voltage input terminal;

The output end of the comparator circuit is a beacon wake-up output end.

A 2.45GHz rail transit precise positioning system beacon device, comprising:

The beacon body and the wake-up circuit described in the present invention; wherein,

The beacon body is electrically connected to the beacon wake-up output terminal of the wake-up circuit.

Compared with the prior art, the wake-up circuit and device for the 2.45 GHz rail transit precise positioning system beacon provided by the present invention have the following beneficial effects:

By adopting a three-stage voltage doubler rectifier circuit, the power efficiency is effectively improved by utilizing the function of the three-stage voltage doubler rectifier circuit, the input voltage is doubled, and sufficient energy can be effectively collected in the 2.45GHz high-frequency band where the signal attenuation is relatively large, thereby quickly waking up the beacon. The wake-up circuit can ensure that the beacon has sufficient power supply when waking up while maintaining low power consumption, thereby meeting the specific needs of the beacon in the rail transit precise positioning system in the 2.45GHz frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

FIG1 is a circuit diagram of a wake-up circuit for a 2.45 GHz rail transit precise positioning system beacon according to an embodiment of the present invention.

FIG2 is a schematic diagram of a primary voltage doubling rectifier circuit of a wake-up circuit of a beacon of a 2.45 GHz rail transit precise positioning system provided in an embodiment of the present invention.

FIG. 3 is a schematic diagram showing the positional relationship between the beacon and the reader.

FIG4 is a schematic diagram of characteristic curves of the rectifier diode HSMS2862 used in the voltage doubler rectifier circuit of the wake-up circuit provided in an embodiment of the present invention at 915 MHz, 2.45 GHz, and 5.8 GHz.

FIG. 5 is a state transition diagram of a wake-up circuit corresponding to a beacon provided by an embodiment of the present invention.

FIG. 6 is a diagram showing the distance of the wake-up circuit corresponding to the beacon and the output voltage of the wake-up circuit provided by an embodiment of the present invention.

FIG. 7 is a current diagram of a beacon in a working mode corresponding to a wake-up circuit provided in an embodiment of the present invention.

FIG8 is a current diagram of a beacon in a sleep mode corresponding to a wake-up circuit provided in an embodiment of the present invention.

Detailed ways

The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the specific content of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

First, the terms that may be used in this article are explained as follows:

The term “and/or” means that either or both of them can be realized at the same time. For example, X and/or Y means both “X” or “Y” and “X and Y”.

The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

Unless otherwise specified or limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this article can be understood according to specific circumstances.

The orientation or position relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the drawings and are only for the convenience and simplification of description, and do not explicitly or implicitly indicate that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation of this document.

The scheme provided by the present invention is described in detail below. The contents not described in detail in the embodiments of the present invention belong to the prior art known to professionals in the field. If the specific conditions are not specified in the embodiments of the present invention, they are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used in the embodiments of the present invention, they are all conventional products that can be purchased commercially.

As shown in FIG1 , an embodiment of the present invention provides a wake-up circuit for a 2.45 GHz rail transit precise positioning system beacon, comprising:

Antenna, impedance matching circuit, three-stage voltage doubler rectifier circuit and comparator circuit; wherein,

The antenna is electrically connected to the total input end of the three-stage voltage doubler rectifier circuit via the impedance matching circuit;

The total output end of the three-stage voltage doubler rectifier circuit is electrically connected to an input end of the comparator circuit;

Another input terminal of the comparator circuit is a comparison voltage input terminal;

The output end of the comparator circuit is a beacon wake-up output end.

Preferably, in the above wake-up circuit, the three-stage voltage doubler rectifier circuit is composed of a first-stage voltage doubler rectifier circuit, a second-stage voltage doubler rectifier circuit and a third-stage voltage doubler rectifier circuit connected in series; wherein,

The input end of the first-stage voltage doubler rectifier circuit serves as a total input end and is electrically connected to the output end of the impedance matching circuit;

The output end of the third-stage voltage doubler rectifier circuit serves as a total output end and is electrically connected to an input end of the comparator circuit.

Preferably, in the above wake-up circuit, in the three-stage voltage doubler rectifier circuit, the first-stage voltage doubler rectifier circuit, the second-stage voltage doubler rectifier circuit and the third-stage voltage doubler rectifier circuit have the same structure, and all include:

Input capacitor, two rectifier diodes and charging capacitor; where,

Two rectifier diodes are connected in series, the positive terminals of the two rectifier diodes are grounded, and the negative terminals serve as output terminals;

The middle of the two rectifier diodes connected in series is used as the input end, and the input capacitor is connected in series to the input end;

The charging capacitor is connected in parallel across the two rectifier diodes connected in series.

Preferably, in the above wake-up circuit, in each stage of the three-stage voltage doubler rectifier circuit, the capacity of the input capacitor and the charging capacitor are both 10pF;

Both rectifier diodes use Schottky detector diode HSMS2862.

Preferably, in the above wake-up circuit, the impedance matching circuit is a π-type impedance matching circuit formed by connecting an inductor and two capacitors; wherein,

The first capacitor is electrically connected between the input end of the inductor and the ground point;

The second capacitor is electrically connected between the output terminal of the inductor and the ground point.

Preferably, in the above impedance matching circuit, the impedance of the impedance matching circuit is 50Ω.

Preferably, in the above wake-up circuit, the comparator circuit is formed by connecting two resistors and a comparator, wherein the two resistors are connected in series, one end of the two resistors connected in series is grounded, and the other end is connected to the positive electrode of the comparison power supply;

The middle point of the two resistors connected in series is connected to the comparison voltage input terminal of the comparator;

The power supply end of the comparator is respectively connected to the positive electrode and the negative electrode of the comparison power supply.

Preferably, in the above wake-up circuit, the antenna adopts a 2.4G RFID ceramic antenna.

The embodiment of the present invention further provides a 2.45 GHz rail transit precise positioning system beacon device, comprising:

The beacon body and the above-mentioned wake-up circuit; wherein,

The beacon body is electrically connected to the beacon wake-up output terminal of the wake-up circuit.

In summary, the wake-up circuit of the embodiment of the present invention, due to the use of a three-stage voltage doubler rectifier circuit, utilizes the function of the three-stage voltage doubler rectifier circuit to double the input voltage, improve the power utilization efficiency, and can effectively collect enough energy in the 2.45GHz high-frequency band where the signal attenuation is relatively large, thereby quickly waking up the beacon; by adding an impedance matching circuit, a large amount of loss caused by the propagation of the RF signal in the wake-up circuit is reduced. The wake-up circuit can ensure that the beacon has sufficient power supply when waking up while maintaining low power consumption, thereby well meeting the specific needs of the beacon in the rail transit precise positioning system in the 2.45GHz frequency band.

In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the wake-up circuit of the 2.45 GHz rail transit precise positioning system beacon provided by the embodiment of the present invention is described in detail below with reference to a specific embodiment.

Example 1

This embodiment provides a wake-up circuit for a 2.45GHz rail transit precise positioning system beacon. The wake-up circuit uses a three-stage voltage doubler rectifier circuit to ensure that sufficient energy can be effectively collected in the 2.45GHz high frequency band where the signal attenuation is relatively large, to ensure the requirements for waking up the beacon. The voltage doubler rectifier circuit is first introduced below, and the design of the voltage doubler rectifier circuit is subsequently explained.

(I) The principle of voltage doubler rectifier circuit:

In the RF wake-up circuit, the analysis of the path loss of radio waves shows that when the radio signal propagates a certain distance in free space, its energy will attenuate. The degree of attenuation is related to the propagation distance and the communication frequency. According to the Friis transmission formula, the free space path loss (fspl, in dB) equation describes the relationship between energy loss and the communication distance d and the communication frequency f:

(1);

In the above formula (1), c is the speed of light. Formula (1) shows that the energy attenuation of wireless signals in space shows an exponential attenuation as the distance increases. This means that when the input signal reaches the RF wake-up circuit, the power is already very small and cannot reach the diode's conduction voltage. And because the commonly used signal frequency in the rail transit positioning system is 2.45GHz, under the influence of ultra-high frequency, the junction capacitance of the diode has an increasingly greater impact on the output of the entire voltage doubler rectifier circuit.

The ideal wake-up circuit does not consume any battery energy of the beacon, but only converts the RF signal sent by the reader into its own energy source, and further generates a DC trigger level to wake up the processor of the active beacon. The passive wake-up strategy can be implemented by a voltage doubler rectifier circuit, the most widely used of which is the Cockcroft-Walton voltage doubler rectifier circuit. The use of a passive wake-up strategy can greatly reduce the power consumption of active electronic tags and eliminate redundant wake-up power consumption.

The voltage doubler rectifier circuit can not only double the voltage of the signal, but also has the function of rectifying the signal. The wake-up circuit often works under passive conditions and has the functions of low input, high voltage, low current, and DC output. Its function is to double the voltage and rectify the input signal. Voltage doubler refers to amplifying a smaller voltage amplitude by multiples to achieve a higher voltage amplitude. Rectification refers to rectifying the alternating current into a DC level, which makes the low-voltage AC signal become a high-voltage DC signal after passing through the voltage doubler rectifier circuit, thereby driving the subsequent circuit. Figure 2 shows the structural schematic diagram of a primary voltage doubler rectifier circuit.

Assume that the input AC signal voltage is U _in . In the positive half cycle of the input voltage, due to the different conduction directions of diodes D1 and D2, the voltage value at point A is higher than that at point B. D1 is turned on, D2 is turned off, and the current flows from point A to point B. The power supply charges capacitor C1, and the charging voltage reaches the maximum value U _in and remains basically unchanged. In the negative half cycle of the input voltage, the voltage value at point B is higher than that at point A. D1 is turned off, D2 is turned on, and the current flows from point B to point A. The power supply charges capacitor C2. At the same time, the voltage direction of the power supply is the same as that of C1. This means that C1 is also the power supply for C2 at this moment, that is, in the process of current flowing from point B to point A, C1 is also charging C2. In addition, due to the charging and discharging time of the capacitor, the voltage of C1 will not be transferred to C2 at one time, but a certain voltage value will be transferred to C2 in each negative half cycle of the input signal. After an infinite number of cycles, the final voltage value of C2 will reach 2U _in . This is the working principle of the voltage doubler rectifier circuit.

According to Kirchhoff's law and the law of conservation of charge, it can be deduced that after n cycles, the voltage value on the resistor R is Will achieve:

(2);

Analyzing the above formula, we can see that after an infinite number of cycles, the voltage of capacitor C2 is basically 2U _in , where U _in represents the input voltage. The larger the capacitor C1, the more charge is transferred from C1 to C2. C2 has:

(3);

The voltage on the resistor R will instantly reach 2U _in , so when selecting capacitors, the capacity of C1 should be as large as possible and the capacity of C2 should be as small as possible.

For a multi-stage voltage doubler rectifier circuit, diodes and capacitors are added to the circuit. The voltage after each voltage doubler is used as the input voltage of the next stage. After being amplified by the subsequent voltage doubler rectifier circuit, the voltage value is doubled. An N-stage voltage doubler circuit can be obtained, and the output voltage is As the number of levels increases, the relationship between the two is:

(4);

Where _Vd is the bias voltage of the diode and _Vc is the input voltage of the diode. Equation (4) determines the requirements of the rectifier for the diode. A simple form of rectifier includes a diode, and the recovered envelope signal, although lower in amplitude, still maintains the same frequency as the original signal. The peak value of the input AC signal must be higher than the bias voltage of the diode in order for the diode to rectify the signal. Since the circuit is basically a half-wave rectifier, a DC level will be generated across the capacitor. The diode is a key component of the rectifier circuit and its parameters directly affect the performance. When selecting a diode, the smaller the resistivity, the better the junction capacitance.

(II) Structure of the three-stage voltage doubler rectifier circuit of the present invention:

The implementation of the wake-up circuit of the present invention and the selection of circuit components will be described below.

In order to double the input weak RF signal to a voltage V _- (8mV) that can be compared by the comparator, and considering the actual situation, a three-stage voltage doubler rectifier circuit is used in series. In fact, it is impossible to increase the output voltage Vout by increasing the number of stages of the voltage doubler rectifier circuit. This is because equation (4) does not take into account the fact that adding diodes, capacitors and PCB lines will waste part of the power of the RF signal. Since the RF signal is very weak in the wake-up circuit, V _c is roughly equal to V _d at this time, and increasing the number of stages will reduce the overall efficiency of the voltage doubler rectifier circuit. Another practical factor that needs to be considered is that the rail transit precise positioning system has extremely high requirements for real-time performance. In the voltage doubler rectifier circuit, the output voltage of the previous stage is equivalent to charging the capacitor of the next stage, and the capacitor charging process takes a certain amount of time. If there are too many voltage doubler stages, the real-time performance of the system cannot be ensured. Therefore, the final circuit uses a three-stage voltage doubler rectifier to meet the performance requirements of the positioning system while maintaining sufficient response speed. The overall structure of the circuit is shown in Figure 1.

The voltage amplification part of the three-stage voltage doubler rectifier circuit is composed of six capacitors and six diodes, among which capacitor C3, capacitor C4 and diode D1 constitute the first-stage voltage doubler rectifier circuit, the input is the radio frequency signal Vin received by the antenna, and the output is Vout1; capacitor C5, capacitor C6 and diode D2 constitute the second-stage voltage doubler rectifier circuit, the input is the output of the first-stage voltage doubler rectifier circuit, and the output is Vout2; capacitor C7, capacitor C8 and diode D3 constitute the third-stage voltage doubler rectifier circuit, the input is the output of the second-stage voltage doubler rectifier circuit, and the output is Vout3, and the voltage signal after voltage doubler is output to the comparator V+, which is used to provide the judgment voltage basis of the comparator circuit. According to the above analysis, if the input voltage is Vin, then Vout1=2Vin, Vout2=2Vout1=4Vin, Vout3=2Vout2=8Vin, in other words, the theoretical value of the output voltage of the three-stage voltage doubler rectifier circuit is eight times the input voltage.

Since the wake-up circuit operates in the 2.45GHz high frequency band, it is difficult for ordinary diodes to meet the voltage doubling requirements. In order to achieve a good voltage doubling effect in the case of three-stage voltage doubling, the diode uses the Schottky detector diode HSMS2862 produced by Avago, which is theoretically suitable for the 5.8GHz frequency band. The characteristics of the diode at 915MHz, 2.45GHz, and 5.8GHz are shown in Figure 4.

It can be observed that the diode can still work normally under very low power input signal. When a -23dBm signal is detected, it can output a voltage of 100mV. For the case of an input signal of -15dBm, the output voltage can theoretically reach 300mV, which can fully meet the design requirements.

In addition, in the wake-up circuit of the present invention, three devices, capacitor C1, capacitor C2 and inductor L1, are introduced to form a π-type impedance matching circuit for impedance matching. Without the impedance matching network formed by these three devices, a large amount of loss is caused by the propagation of the RF signal in the wake-up circuit, which greatly reduces the working effect of the three-stage voltage doubler rectifier circuit. By adding the impedance matching circuit, the maximum power transmission between the antenna and the rest of the wake-up circuit is achieved, and the incident RF signal is introduced into the wake-up circuit to the maximum extent, thereby improving the overall performance.

Referring to FIG3 , the beacon working process using the wake-up circuit of the present invention is as follows: when the train arrives, the beacon needs to transmit information, and the reader sends a radio frequency signal. The beacon receives the radio frequency signal through the antenna of the wake-up circuit at the receiving end, and matches the antenna (matched to 50Ω) through an impedance matching circuit. The three-stage voltage doubler rectifier circuit rectifies and amplifies the radio frequency signal for further processing by the comparator. When the output voltage of the three-stage voltage doubler rectifier circuit is higher than the reference voltage of the comparator (the comparator adopts the model TLV7021, and the lowest reference voltage that can be compared is 8mV. By setting the values of the resistors R1 and R2 of the voltage divider circuit, a voltage of 8mV is generated to V-), the comparator will generate a high-level voltage "1"; conversely, when the output voltage of the three-stage voltage doubler rectifier circuit is lower than the reference voltage of the comparator, a low-level voltage "0" is generated. When the high-level voltage is generated, the MCU of the beacon will trigger an edge interrupt, so that the beacon switches from sleep mode to working mode, and enters the interrupt processing function to send data to the reader. After the data is sent, the beacon enters sleep mode again and waits for the next wake-up.

The beacon mainly includes two working modes, and its state diagram is shown in Figure 5, which shows the state transition relationship diagram of the beacon in the working mode and the sleep mode:

(1) Sleep mode: When the beacon does not receive the signal from the undercar reader, the beacon enters sleep mode to reduce power consumption and increase the service life of the beacon;

(2) Working mode: When a train passes through a beacon section, the signal from the undercar reader activates the beacon to enter working mode. In working mode, the beacon sends data to the reader by backscattering, and the reader parses the data and transmits it to the host computer to achieve accurate positioning of the train.

The wake-up circuit of the present invention is designed for beacons in the 2.45GHz rail transit precise positioning system, which can effectively reduce power consumption, thereby improving the energy efficiency and service life of the beacon, so as to meet the needs of low-power wireless transmission systems in data transmission, and well solve the problem that the beacons in the current rail transit precise positioning system are in a high-power wake-up state for a long time and have a low service life. Next, the experimental analysis will be carried out from two aspects:

(1) Distance test: The reader uses TagMaster's industrial reader with a transmission power of 10mW. In the experiment, the center of the antenna surface of the reader is selected as the origin, with the x-axis perpendicular to the antenna surface and the direction away from the antenna surface of the reader along the x-axis. By using a multimeter to measure the voltage after the three-level voltage doubling output, the experiment obtained the relationship between the distance and the output voltage. The result is shown in Figure 6, which shows that in the process of the wake-up beacon moving from near to far away from the reader, as the distance between the beacon and the reader gradually increases, the voltage output by the wake-up circuit gradually decreases. When the distance from the reader is 225cm, the output voltage of the three-level voltage doubling is 8mV. The farthest distance that the beacon can communicate with the reader is 2.25 meters, and under normal circumstances, the communication distance between the reader and the beacon is only 0.35 meters, which meets the application requirements of beacons in rail transit precise positioning systems.

(2) Life test: According to the operation time of the subway line, from 6:06 am to 10:06 pm, the train interval is 5 minutes, and the stop time at each platform is 30 seconds. The beacon at the platform works for 1.6 hours a day and sleeps for 22.4 hours. The measured working current of the beacon in working mode and sleep mode are shown in Figure 7 and Figure 8 respectively. Figure 7 shows that the current measured by the beacon in working mode is 278.09uA, and Figure 8 shows that the current measured by the beacon in sleep mode is 46.80uA.

The MCU model selected is Ti MSP430F5505. The current of the beacon in working mode is measured to be 278.09uA, and the current in sleep mode is 46.80uA. Therefore, the power consumption of the beacon in one day can be calculated as 1.6h×278.09uA+22.4h×46.80uA=1494.864uAh≈1.495mAh, see Table 1:

Table 1 shows the calculation results of beacon power consumption and lifespan

Power consumption per day 1 year power consumption (365 days) Battery 10-year self-consumption life 1.495mAh 545.675mAh 2700mAh About 11.54 years

After calculation, when a disposable industrial lithium battery with a capacity of 9000 mAh is used, the life of the beacon can reach 11.54 years. Table 1 shows that the life of the beacon using the wake-up circuit of the present invention is significantly improved and can meet application requirements.

Through testing, the distance and life of the beacon using the wake-up circuit of the present invention meet the requirements of the rail transit precise positioning system for beacons. The wake-up circuit using this design is feasible in the 2.45GHz frequency band, fully meets actual needs, and also has the potential to be expanded to other 2.45GHz wake-up applications.

Example 2

Referring to FIG. 1 , this embodiment provides a wake-up circuit for a 2.45GHz rail transit precise positioning system beacon, which is composed of a ceramic antenna, an impedance matching circuit, a three-stage voltage doubler rectifier circuit and a comparator circuit; wherein the ceramic antenna adopts a domestically produced 2.4G RFID ceramic antenna produced by Ruodian Electronic Technology Co., Ltd. After testing, the ceramic antenna exhibits good directivity, which helps to achieve precise positioning of the beacon. The impedance matching circuit is composed of an inductor and two capacitors. The impedance is tested by a vector network analyzer to achieve an impedance of 50Ω for the best effect. In the three-stage voltage doubler rectifier circuit, the Schottky detector diode HSMS2862 produced by Avago is used, and the capacitance value is 10pF. The comparator model is TLV7021, which has very low power consumption and is very suitable as a component of the wake-up circuit. The comparison voltage of the comparator is set to 8mV, so that the wake-up circuit is deployed.

The output pin of the comparator is connected to a specific GPIO port of the beacon's MCU, and the GPIO port is set to edge-triggered interrupt mode. The initial state of the MCU is set to sleep mode. When the comparator outputs a high level, it indicates that a train has arrived at this moment, and the beacon needs to send a positioning data packet to the reader on the train. At this time, the MCU enters the interrupt function and sends a data packet to the reader. After sending the data packet, if the output of the comparator is still high, it continues to send data packets; if the output of the comparator is low at this time, it indicates that the train has left the beacon range, and the beacon switches to sleep mode, waiting for the next train to arrive to wake up the beacon.

The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims (9)

1. A wake-up circuit for a 2.45GHz rail transit precise positioning system beacon, comprising: Antenna, impedance matching circuit, three-stage voltage doubler rectifier circuit and comparator circuit; wherein, The antenna is electrically connected to the total input end of the three-stage voltage doubler rectifier circuit via the impedance matching circuit; The total output end of the three-stage voltage doubler rectifier circuit is electrically connected to an input end of the comparator circuit; Another input terminal of the comparator circuit is a comparison voltage input terminal; The output end of the comparator circuit is a beacon wake-up output end. 2. The wake-up circuit of the 2.45GHz rail transit precise positioning system beacon according to claim 1 is characterized in that the three-stage voltage doubler rectifier circuit is composed of a first-stage voltage doubler rectifier circuit, a second-stage voltage doubler rectifier circuit and a third-stage voltage doubler rectifier circuit connected in series; wherein, The input end of the first-stage voltage doubler rectifier circuit serves as a total input end and is electrically connected to the output end of the impedance matching circuit; The output end of the third-stage voltage doubler rectifier circuit serves as a total output end and is electrically connected to an input end of the comparator circuit. 3. The wake-up circuit of the 2.45GHz rail transit precise positioning system beacon according to claim 2, characterized in that, in the three-stage voltage doubler rectifier circuit, the first-stage voltage doubler rectifier circuit, the second-stage voltage doubler rectifier circuit and the third-stage voltage doubler rectifier circuit have the same structure, and all include: Input capacitor, two rectifier diodes and charging capacitor; where, Two rectifier diodes are connected in series, the positive terminals of the two rectifier diodes are grounded, and the negative terminals serve as output terminals; The middle of the two rectifier diodes connected in series is used as the input end, and the input capacitor is connected in series to the input end; The charging capacitor is connected in parallel across the two rectifier diodes connected in series. 4. The wake-up circuit of the 2.45GHz rail transit precise positioning system beacon according to claim 3, characterized in that in each stage of the three-stage voltage doubler rectifier circuit, the capacity of the input capacitor and the charging capacitor are both 10pF; Both rectifier diodes use Schottky detector diode HSMS2862. 5. The wake-up circuit of the 2.45 GHz rail transit precise positioning system beacon according to any one of claims 1 to 4, characterized in that the impedance matching circuit is a π-type impedance matching circuit formed by connecting an inductor and two capacitors; wherein, The first capacitor is electrically connected between the input end of the inductor and the ground point; The second capacitor is electrically connected between the output terminal of the inductor and the ground point. 6 . The wake-up circuit of the 2.45 GHz rail transit precise positioning system beacon according to claim 5 , wherein the impedance of the impedance matching circuit is 50Ω. 7. The wake-up circuit of the 2.45 GHz rail transit precise positioning system beacon according to any one of claims 1 to 4, characterized in that the comparator circuit is formed by connecting two resistors and a comparator, wherein: Two resistors are connected in series, one end of the two resistors connected in series is grounded, and the other end is connected to the positive pole of the power supply; The middle point of the two resistors connected in series is connected to the comparison voltage input terminal of the comparator; The power supply end of the comparator is respectively connected to the positive electrode and the negative electrode of the comparison power supply. 8. The wake-up circuit of the 2.45 GHz rail transit precise positioning system beacon according to any one of claims 1 to 4, characterized in that the antenna adopts a 2.4G RFID ceramic antenna. 9. A 2.45GHz rail transit precise positioning system beacon device, characterized by comprising: A beacon body and a wake-up circuit as described in any one of claims 1 to 8; wherein, The beacon body is electrically connected to the beacon wake-up output terminal of the wake-up circuit.