Intelligent automobile key based on RFID and control method

Abstract

The invention discloses an intelligent automobile key based on RFID and a control method, and relates to the technical field of automobile electronic theft prevention, the intelligent automobile key comprises a main control chip AIP300, a radio frequency chip CMT2110, a PCB loop antenna and a receiving chip WF490RE; the main control chip AIP300 is connected with the radio frequency chip CMT2110 through an SPI (Serial Peripheral Interface) bus, the radio frequency chip CMT2110 is also connected with the PCB loop antenna, and the PCB loop antenna is also connected with the receiving chip WF490RE. According to the invention, the transmitting signal of the automobile intelligent key achieves the function of omnidirectional coverage, the problem of signal coverage range in the prior art is solved, and the problem of electromagnetic interference resistance in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile electronic anti-theft, and in particular to an RFID-based intelligent automobile key and a control method thereof. Background Art

[0002] The car intelligent keyless entry system is referred to as PKE (PASSIVE KEYLESS ENTER). This product adopts RFID (Radio Frequency Identification) wireless radio frequency technology and vehicle identity coding recognition system, applies the development solution of miniaturized and low-power radio frequency antenna, integrates the remote control system and keyless system, uses the traditional vehicle circuit protection, realizes dual radio frequency system and dual anti-theft protection, and provides convenience and safety for car owners.

[0003] At present, the key response signal of the PKE system can reach about 100 meters. When a 125khz signal acquisition device is placed next to the car, the 125khz signal just collected is transmitted through radio. If the owner is close to the car, the car will be unlocked directly. If the distance between the car key and the car exceeds the signal coverage range of the key, a relay is needed to send the signal transmitted by the key to the signal acquisition device next to the car and play it again, creating the illusion that the key is near the vehicle.

[0004] In this case, if there are 315 modules or other relay devices around the vehicle, but there are no 125khz relay devices, the PKE system is vulnerable to malicious use in terms of signal coverage due to near-field communication, which poses certain security risks. In addition, since the PKE system relies on two-way communication of low frequency and radio frequency for complex two-way identity authentication, its security is similar to that of engine anti-theft. If the anti-theft host does not receive the signal from the remote control or receives an erroneous signal, the host cannot process it correctly, which further illustrates the potential security issues of the PKE system. Summary of the invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the prior art, specifically the potential safety hazards in the signal coverage of the PKE system, and specifically provide an RFID-based smart car key and control method, as follows:

[0006] 1) In the first aspect, the present invention provides an RFID-based smart car key, and the specific technical solution is as follows: comprising: a main control chip AIP300, a radio frequency chip CMT2110, a PCB loop antenna and a receiving chip WF490RE;

[0007] The main control chip AIP300 is connected to the radio frequency chip CMT2110 via an SPI bus, the radio frequency chip CMT2110 is also connected to the PCB loop antenna, and the PCB loop antenna is also connected to the receiving chip WF490RE.

[0008] The beneficial effects of the RFID-based smart car key provided by the present invention are as follows:

[0009] By adopting the AIP300 chip and using the chip's immo function, the car smart key's transmission signal can achieve omnidirectional coverage, overcoming the signal coverage problem in the prior art. By adopting the WF490REE chip and using the chip's wide receiving bandwidth, high receiving sensitivity and built-in image suppression function, the anti-theft host can solve the problem of not receiving the remote control signal or receiving the wrong signal according to the signal transmitted by the car smart key, overcoming the electromagnetic interference problem in the prior art.

[0010] Based on the above solution, the present invention can also be improved as follows.

[0011] Furthermore, the main control chip AIP300 is also connected to an LED indicator light.

[0012] Further, the PCB loop antenna is a loop antenna matching circuit, specifically comprising: a first inductor, a second inductor and a first capacitor;

[0013] One end of the first inductor is connected to the power supply end, and the other end of the first inductor is connected to the RF chip CMT2110; one end of the second inductor is connected to the RF chip CMT2110, and the other end of the second inductor is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the receiving chip WF490RE.

[0014] Further, the loop antenna matching circuit further includes: a second capacitor;

[0015] One end of the second capacitor is connected to one end of the first inductor, and the other end of the second capacitor is connected to the first analog ground.

[0016] Further, the loop antenna matching circuit further includes: a third capacitor;

[0017] One end of the third capacitor is connected to the RF chip CMT2110, and the other end of the third capacitor is connected to the second analog ground.

[0018] Furthermore, it also includes:

[0019] The transmission circuit between the RF chip CMT2110 and the receiving chip WF490RE is impedance matched by using a Smith chart.

[0020] 2) In a second aspect, the present invention further provides an RFID-based smart car key control method, which adopts the RFID-based smart car key structure described in the first aspect, and the specific technical solution is as follows:

[0021] S1, installing a power supply on the key to be controlled, initializing the key to be controlled according to the receiving chip WF490RE, so that the key to be controlled after the initialization setting according to the receiving chip WF490RE enters a sleep mode;

[0022] S2, obtaining a wake-up instruction for the key to be controlled, and controlling the main control chip AIP300 inside the key to be controlled to detect the power supply voltage value of the key to be controlled according to the wake-up instruction;

[0023] S3, when the power supply voltage value is greater than a preset value, the radio frequency chip CMT2110 inside the key to be controlled transmits a key wake-up message to the vehicle to be unlocked through the PCB ring antenna, so that the vehicle to be unlocked is unlocked by pressing a key.

[0024] The beneficial effects of the RFID-based smart car key control method provided by the present invention are as follows:

[0025] On the basis of adopting WF490RE chip, AIP300 chip and CMT2110 chip to obtain the corresponding characteristics of the chip, different wake-up methods are also used to ensure the power consumption of the key to be controlled and extend the battery life of the key to be controlled.

[0026] Based on the above solution, the present invention can also be improved as follows.

[0027] Furthermore, it also includes:

[0028] S4, when the power supply voltage value is less than a preset value, the radio frequency chip CMT2110 inside the key to be controlled transmits a low-frequency wake-up message to the vehicle to be unlocked through the PCB ring antenna, so that the vehicle to be unlocked is unlocked through a low-frequency signal.

[0029] Further, the wake-up instruction includes: the wake-up instruction includes: a key wake-up instruction and a low-frequency wake-up instruction.

[0030] Furthermore, the low-frequency wake-up instruction is obtained by the receiving chip WF490RE receiving a low-frequency antenna signal emitted by the vehicle to be unlocked when the key to be controlled is within a preset range of the vehicle to be unlocked. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0032] Figure 1 This is a schematic structural diagram of an RFID-based smart car key according to an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of a ring matching circuit according to an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of a Smith chart for impedance matching of a transmission circuit between a radio frequency chip CMT2110 and a receiving chip WF490RE according to an embodiment of the present invention;

[0035] Figure 4 The figure is a flow chart of a method for controlling a smart automobile key based on RFID according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] like Figure 1 As shown, an RFID-based smart car key according to an embodiment of the present invention includes: a main control chip AIP300, a radio frequency chip CMT2110, a PCB loop antenna and a receiving chip WF490RE;

[0038] The main control chip AIP300 is connected to the RF chip CMT2110 through the SPI bus. The RF chip CMT2110 is also connected to the PCB loop antenna, and the PCB loop antenna is also connected to the receiving chip WF490RE.

[0039] The beneficial effects of the RFID-based smart car key provided by the present invention are as follows:

[0040] By adopting the AIP300 chip and using the chip's immo function, the car smart key's transmission signal can achieve omnidirectional coverage, overcoming the signal coverage problem in the prior art. By adopting the WF490REE chip and using the chip's wide receiving bandwidth, high receiving sensitivity and built-in image suppression function, the anti-theft host can solve the problem of not receiving the remote control signal or receiving the wrong signal according to the signal transmitted by the car smart key, overcoming the electromagnetic interference problem in the prior art.

[0041] The main control chip AIP300 refers to: Wuxi Zhongwei Aixin AIP300. The basic characteristics and advantages of AIP300 are as follows:

[0042] (1) 3D immobilizer (3D anti-theft system); this means that the key using this chip can be immobilized in all directions;

[0043] (2) immo uses half-duplex mode, which is more than twice as far as full-duplex mode. Full-duplex means that signals can be transmitted in both directions simultaneously (instantaneously) (A→B and B→A, telephone), while half-duplex means that signals can be transmitted in only one direction at a time (A→B or B→A, walkie-talkie).

[0044] (3) Support anti-collision function, which can identify and select keys using the chip at the same time;

[0045] (4) Supports high Q value (Q value, quality factor) operation; AIP300 integrates resonant frequency trimming; the size of the quality factor Q value of the frequency selection network indicates the quality of its selectivity. The higher the Q value, the better its selectivity, the narrower the passband, and the stronger the anti-interference ability.

[0046] The RF chip CMT2110 refers to: Huapuwei's CMT2110, Huapuwei's CMT2110 is a characteristic single-chip fractional-N frequency division (N frequency division refers to reducing the frequency of a single frequency signal to 1 / N of the original) PLL (Phase Locked Loop, phase-locked loop) transmitter IC (integrated circuit, integrated circuit / microchip, etc.), suitable for 315 / 434 / 869 / 915MHz (ISM / SRD) frequency bands. In addition, CMT2110 also has the following characteristics and advantages:

[0047] (1) Multi-channel capability;

[0048] (2) Programmable OOK / ASK / FSK modulation characteristics;

[0049] (3) Programmable transmit output power;

[0050] (4) Low power consumption, the transmitting current is 7mA at 6dBm;

[0051] (5) Independent power-down mode, suitable for oscillator and PLL, 50nA;

[0052] (6) Extremely low number of external components;

[0053] (7) On-chip VCO (voltage controlled oscillator) and PLL loop filter.

[0054] SPI bus refers to: Serial Peripheral Interface, which is a communication bus and is an existing technology.

[0055] The receiving chip WF490RE refers to the WF490RE chip of Weifengheng Technology Co., Ltd., which uses WF490RE as the main controller and completes the function of receiving the transmitter signal. The basic characteristics and advantages of this chip are as follows:

[0056] (1) High receiving sensitivity (2kbps, BER 10E-2) -113dBm@315MHz -113dBm@433.92MHz;

[0057] (2) Low power consumption: 0.01uA / 3.3V@Shut Down Mode;

[0058] (3) Data rate: ≤10kbps;

[0059] (4) Built-in image suppression, good anti-interference performance;

[0060] (5) Receiving bandwidth: ±320KHz;

[0061] (6) High ESD protection standard: ±8KV HBM.

[0062] The smart car key in the present invention uses Wuxi Zhongwei Aixin AIP300 and Huapuwei's CMT2110 as the core to build the entire transmitter PCBA circuit diagram. AIP300 is packaged together with CMT2110 through the internal SPI bus to realize the functions of PKE and immobilizer, and has rich functional characteristics and safety performance. It should be noted that some foreign devices can also meet this requirement, but based on the current design concept, parts need to be localized, so these two chips are selected as the transmitter PCBA (Printed Circuit Board Assembly) circuit design in the present invention.

[0063] The PCB loop antenna is a loop antenna matching circuit. In another embodiment of the present invention, the loop antenna matching circuit specifically includes: a first inductor, a second inductor and a first capacitor; one end of the first inductor is connected to the power supply end, and the other end of the first inductor is connected to the RF chip CMT2110; one end of the second inductor is connected to the RF chip CMT2110, the other end of the second inductor is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the receiving chip WF490RE.

[0064] The loop antenna matching circuit also includes: a second capacitor; one end of the second capacitor is connected to one end of the first inductor, and the other end of the second capacitor is connected to the first analog ground.

[0065] The loop antenna matching circuit also includes: a third capacitor; one end of the third capacitor is connected to the RF chip CMT2110, and the other end of the third capacitor is connected to the second analog ground.

[0066] like Figure 2 , is a schematic diagram of a ring matching circuit of the present invention, the first inductor is 100nH, the second inductor is 39nH, the first capacitor is 7pF, the second capacitor is 1nF, and the third capacitor is 4pF. The second inductor and the first capacitor are connected in series to form a low-pass filter, which is used to suppress high-order harmonics. The second inductor, the first capacitor and the third capacitor together form a π-type matching network to achieve impedance matching for the high-frequency antenna. The role of the second capacitor is to reduce and eliminate the power supply noise interference at the output end of the power amplifier. The role of the first inductor and the second capacitor connected in series is to form a DC path while playing a good impedance matching role.

[0067] The benefits of adopting the above solution are:

[0068] Through the loop antenna matching circuit, its direction is an omnidirectional antenna, which solves the signal coverage problem of the remote control transmitter.

[0069] In another embodiment of the present invention, it further includes: impedance matching of the transmission circuit between the RF chip CMT2110 and the receiving chip WF490RE is performed through a Smith chart.

[0070] Design the RF drive circuit for CMT2110 and improve the antenna matching. Since the chip is highly integrated and has fewer peripheral circuits, an important part of the drive circuit design is to perform impedance matching on the transmission network connecting CMT2110 and WF490RE in the drive circuit. In the matching, the impedance after connecting the transmission network is required to be around 50Ω in order to achieve impedance matching with the standard antenna. The matching process is performed using the Smith chart. The matching of the transmission network using the Smith chart is shown in the figure below. Figure 3 As shown. Smith chart refers to: Smith chart is a calculation diagram of a family of circles of normalized input impedance (or admittance) equivalent value plotted on a reflection system dispersion plane. It is a chart used in electrical and electronic engineering, mainly used for impedance matching of transmission lines. It is an existing technology and will not be described in detail.

[0071] Furthermore, the main control chip AIP300 is also connected to an LED indicator light, which is used as a prompt when the car key transmits a signal and responds to a signal.

[0072] like Figure 4As shown, the present invention also provides an RFID-based smart car key control method, using the above-mentioned RFID-based smart car key structure, the method includes:

[0073] S1, install a power supply on the key to be controlled, initialize the key to be controlled according to the receiving chip WF490RE, and make the key to be controlled enter the sleep mode after the initialization setting according to the receiving chip WF490RE;

[0074] S2, obtaining a wake-up instruction for the key to be controlled, and controlling the main control chip AIP300 inside the key to be controlled to detect the power supply voltage value of the key to be controlled according to the wake-up instruction;

[0075] S3, when the power supply voltage value is greater than the preset value, the radio frequency chip CMT2110 inside the key to be controlled transmits a key wake-up message to the vehicle to be unlocked through the PCB loop antenna, so that the vehicle to be unlocked is unlocked by pressing the key.

[0076] The beneficial effects of the RFID-based smart car key control method provided by the present invention are as follows:

[0077] On the basis of adopting WF490RE chip, AIP300 chip and CMT2110 chip to obtain the corresponding characteristics of the chip, different wake-up methods are also used to ensure the power consumption of the key to be controlled and extend the battery life of the key to be controlled.

[0078] S1, install a power supply on the key to be controlled, initialize the key to be controlled according to the receiving chip WF490RE, and make the key to be controlled enter the sleep mode after the initialization setting according to the receiving chip WF490RE.

[0079] The key to be controlled refers to: a car key using the above-mentioned RFID-based smart car key structure.

[0080] The power source refers to: the commonly used one is a button battery, which is installed in the key to be controlled.

[0081] Initialization setting means: according to the receiving chip WF490RE as the main control chip, the low-frequency receiving module in the key to be controlled is initialized. The initialization content can be the clock or port of the key to be controlled. After the initialization setting is completed, the key to be controlled enters the sleep mode according to WF490RE. In sleep mode, the key to be controlled is in the lowest power consumption, and the sleep current is only 20nA, which ensures that the number of uses of the smart key is more than 30,000 times.

[0082] S2, obtaining a wake-up instruction for the key to be controlled, and controlling the main control chip AIP300 inside the key to be controlled to detect the power supply voltage value of the key to be controlled according to the wake-up instruction.

[0083] The wake-up commands include: key wake-up commands and low-frequency wake-up commands.

[0084] The key wake-up command is obtained by the user pressing the corresponding button on the key to be controlled.

[0085] The low-frequency wake-up command is obtained by receiving the low-frequency antenna signal from the vehicle to be unlocked by the receiving chip WF490RE when the key to be controlled is within the preset range of the vehicle to be unlocked. Among them:

[0086] The preset range refers to all areas within a circle with the vehicle to be unlocked as the center and a fixed value as the radius. The radius value can be adjusted according to actual needs.

[0087] After the key to be controlled, which is in sleep mode and has completed the initialization of the low-frequency receiving module, obtains the wake-up command, the main control chip AIP300 will detect the current power supply voltage value of the key to be controlled before executing the wake-up command to confirm whether the current battery voltage is greater than 2.5V. If the battery voltage is greater than 2.5V, the main control chip AIP300 will proceed with the next instruction. If the battery voltage is less than 2.5V, the wireless key will automatically enter the key sleep mode.

[0088] The function of judging the voltage is to check whether a key is pressed. If so, the battery voltage will be greater than 2.5V, and the current key command will be sent. If no key is pressed, the battery voltage is less than 2.5V, and the main control chip AIP300 will enter sleep mode with the lowest power consumption. The sleep current is only 20nA, which ensures that the smart key can be used more than 30,000 times.

[0089] There are two ways to wake up a wireless smart key: one is to wake up by remote control button, that is, the owner triggers the wake-up by pressing the remote control button on the smart key. This method is key wake-up, also known as RKE (Remote Keyless Entry) function. After the wake-up is completed, the key will enter the message preparation stage. The other is low-frequency wake-up, that is, the wireless smart key wakes up by automatically receiving the low-frequency signal sent by the low-frequency antenna from the vehicle. This wake-up method is also called PEPS (Passive Entry Passive Start) function.

[0090] S3, when the power supply voltage value is greater than the preset value, the RF chip CMT2110 inside the key to be controlled transmits a key wake-up message to the vehicle to be unlocked through the PCB loop antenna, so that the vehicle to be unlocked is unlocked by pressing the key.

[0091] The preset value refers to: a power supply voltage value set according to actual needs, and in this embodiment, it is 2.5V.

[0092] When the power supply voltage is greater than 2.5V, the RF chip CMT2110 inside the key to be controlled transmits a key wake-up message to the vehicle to be unlocked through the PCB ring antenna, so that the vehicle to be unlocked can be unlocked by pressing the key, which is the above-mentioned key wake-up, also known as the RKE function.

[0093] Further, it also includes: S4, when the power supply voltage value is less than a preset value, a low-frequency wake-up message is transmitted to the vehicle to be unlocked through a PCB ring antenna according to the radio frequency chip CMT2110 inside the key to be controlled, so that the vehicle to be unlocked is unlocked through a low-frequency signal.

[0094] When the power supply voltage is less than 2.5V, it means that the user has not pressed the corresponding button of the key to be controlled, but the key to be controlled is within the preset range of the vehicle to be unlocked. At this time, the receiving chip WF490RE receives the low-frequency antenna signal from the vehicle to be unlocked and obtains a low-frequency wake-up instruction. According to the low-frequency wake-up instruction, the RF chip CMT2110 inside the key to be controlled transmits a low-frequency wake-up message to the vehicle to be unlocked through the PCB ring antenna, so that the vehicle to be unlocked is unlocked through the low-frequency signal. That is, the above-mentioned low-frequency signal wake-up, this wake-up method is also called PEPS function.

[0095] The benefits of adopting the above solution are as follows:

[0096] By using the AIP300 chip and the chip's immo function, the car smart key transmission signal can achieve omnidirectional coverage, overcoming the signal coverage problem in the technical background. By using the WF490RE chip and the chip's wide receiving bandwidth, high receiving sensitivity and built-in image suppression function, the car smart key transmission signal can solve the problem that the anti-theft host cannot receive the remote control signal or the wrong signal, overcoming the electromagnetic interference problem in the technical background. All localization means that all domestic chips are used.

[0097] In the above embodiments, although the steps are numbered S1, S2, etc., these are only specific embodiments given by the present invention. Those skilled in the art may adjust the execution order of S1, S2, etc. according to actual conditions, which is also within the protection scope of the present invention. It can be understood that in some embodiments, some or all of the above embodiments may be included.

[0098] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects and represent the definition of a specific order or sequence. The order of use of similar objects can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than the order shown or described.

[0099] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. An RFID-based smart car key, characterized in that: include: Main control chip AIP300, RF chip CMT2110, PCB loop antenna and receiving chip WF490RE; The main control chip AIP300 is connected to the radio frequency chip CMT2110 via an SPI bus, the radio frequency chip CMT2110 is also connected to the PCB loop antenna, and the PCB loop antenna is also connected to the receiving chip WF490RE.

2. The RFID-based smart car key according to claim 1, characterized in that: The main control chip AIP300 is also connected to the LED indicator light.

3. The RFID-based smart car key according to claim 1, characterized in that: The PCB loop antenna is a loop antenna matching circuit, specifically comprising: a first inductor, a second inductor and a first capacitor; One end of the first inductor is connected to the power supply end, and the other end of the first inductor is connected to the RF chip CMT2110; one end of the second inductor is connected to the RF chip CMT2110, and the other end of the second inductor is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the receiving chip WF490RE.

4. The RFID-based smart car key according to claim 3, characterized in that: The loop antenna matching circuit further includes: a second capacitor; One end of the second capacitor is connected to one end of the first inductor, and the other end of the second capacitor is connected to the first analog ground.

5. The RFID-based smart car key according to claim 3, characterized in that: The loop antenna matching circuit further includes: a third capacitor; One end of the third capacitor is connected to the RF chip CMT2110, and the other end of the third capacitor is connected to the second analog ground.

6. The RFID-based smart car key according to claim 3, characterized in that: Also includes: The transmission circuit between the RF chip CMT2110 and the receiving chip WF490RE is impedance matched by using a Smith chart.

7. A smart car key control method based on RFID, characterized in that: Using the RFID-based smart car key structure described in claim 1, the method includes: S1, installing a power supply on the key to be controlled, initializing the key to be controlled according to the receiving chip WF490RE, so that the key to be controlled after the initialization setting according to the receiving chip WF490RE enters a sleep mode; S2, obtaining a wake-up instruction for the key to be controlled, and controlling the main control chip AIP300 inside the key to be controlled to detect the power supply voltage value of the key to be controlled according to the wake-up instruction; S3, when the power supply voltage value is greater than a preset value, the radio frequency chip CMT2110 inside the key to be controlled transmits a key wake-up message to the vehicle to be unlocked through the PCB ring antenna, so that the vehicle to be unlocked is unlocked by pressing a key.

8. The RFID-based smart car key control method according to claim 7, characterized in that: Also includes: S4, when the power supply voltage value is less than a preset value, the radio frequency chip CMT2110 inside the key to be controlled transmits a low-frequency wake-up message to the vehicle to be unlocked through the PCB ring antenna, so that the vehicle to be unlocked is unlocked through a low-frequency signal.

9. The RFID-based smart car key control method according to claim 7, characterized in that: The wake-up instructions include: key wake-up instructions and low-frequency wake-up instructions.

10. The RFID-based smart car key control method according to claim 9, characterized in that: The low-frequency wake-up instruction is obtained by the receiving chip WF490RE receiving a low-frequency antenna signal emitted by the vehicle to be unlocked when the key to be controlled is within a preset range of the vehicle to be unlocked.

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