Full-band dynamic matching low-power intelligent digital car key

Abstract

The application belongs to the field of automobile electronics and wireless communication technology, and specifically relates to a full-band dynamic matching low-power intelligent digital car key, which comprises a main control chip, a Bluetooth communication module, a wideband radio frequency transmitting chip and a transmitting antenna; between the wideband radio frequency transmitting chip and the transmitting antenna, a set of antenna hardware adjusting circuit capable of automatically switching with frequency and directly controlled by the main control chip is arranged; when the main control chip changes the output frequency of the wideband radio frequency transmitting chip according to an external instruction, the main control chip synchronously outputs a physical control signal, switches the internal conduction path of the antenna hardware adjusting circuit, so that the hardware state of the transmitting antenna is always adapted to the current output frequency. The intelligent digital car key can dynamically change the transmitting frequency through a mobile terminal to adapt to different vehicles, and has an antenna hardware state frequency adjustment mechanism and a hierarchical false wake-up prevention mechanism.

Description

Technical Field

[0001] This invention relates to the fields of automotive electronics and wireless communication technology, and in particular to a full-band dynamic matching low-power smart digital car key. Background Technology

[0002] As the wave of automotive intelligence continues to advance, traditional physical keys are gradually being replaced by digital car keys. Digital car keys allow users to lock, unlock, start, and remotely control their vehicles via smartphones or smart wearable devices, greatly improving the convenience of car use.

[0003] Currently, various universal digital car keys exist in the automotive aftermarket, designed to be compatible with vehicles using different communication frequencies (such as 315MHz, 433MHz, or 868MHz) by changing the transmission frequency of their internal chips. However, in practical engineering implementation, existing technologies suffer from the following insurmountable technical defects:

[0004] 1. Transmission Conflict Between RF Chip Frequency Switching and Fixed Antenna Hardware: Existing universal keys only modify the RF chip's transmission frequency via software instructions. However, the antenna hardware circuitry on the circuit board remains fixed. When the transmission frequency undergoes a significant shift (e.g., from 315MHz to 868MHz), the fixed antenna hardware circuitry cannot adapt to the new high-frequency signal, leading to a sharp increase in energy loss within the antenna. This directly results in extremely weak remote control signals; a remote control distance that was originally 50 meters may be reduced to 5 meters, failing to meet normal usage requirements.

[0005] 2. Rapid Battery Depletion Due to a Single Wake-up Mechanism: Existing smart digital keys typically have a built-in Bluetooth module for communication with mobile phones, and their wake-up logic is relatively simple: as long as an external Bluetooth signal is received, it will directly wake up the high-power main control chip. In the complex electromagnetic environment of cities, filled with various irrelevant mobile phone and Bluetooth device signals, the main control chip will be frequently and erroneously woken up, causing the limited battery power of the card key to be depleted within a few days.

[0006] 3. Frequency Shift Issues Under Extreme Temperatures: In environments such as high temperatures and direct sunlight during summer, the electronic components inside the digital key may undergo physical deformation due to heat, causing a shift in the frequency of the actually transmitted signal. For example, the originally set 433.92MHz signal may shift to 433.95MHz, making it unrecognizable by the vehicle's receiver and resulting in the door being unable to unlock. Summary of the Invention

[0007] 1. Technical problems to be solved

[0008] The purpose of this invention is to solve the problems of multi-band compatibility, standby power consumption, and temperature interference in existing technologies, and to propose a full-band dynamic matching low-power intelligent digital car key.

[0009] 2. Technical Solution

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] In the first aspect, this application provides a full-band dynamic matching low-power smart digital car key, which includes a main control chip, a Bluetooth communication module, a wideband radio frequency transmitting chip, and a transmitting antenna;

[0012] Between the broadband radio frequency transmitting chip and the transmitting antenna, there is a set of antenna hardware adjustment circuit that is directly controlled by the main control chip and can automatically switch with the frequency.

[0013] When the main control chip changes the output frequency of the broadband radio frequency transmitter chip according to external instructions, the main control chip synchronously outputs physical control signals to switch the internal conduction path of the antenna hardware adjustment circuit, so that the hardware state of the transmitting antenna is always adapted to the current output frequency.

[0014] In one possible implementation, the antenna hardware adjustment circuit that can automatically switch with frequency includes multiple sets of capacitor and inductor branches of different specifications and controlled miniature electronic switches.

[0015] In one possible implementation, the main control chip stores a table of correspondence between the transmission frequency and the capacitor-inductor branch. The main control chip selects the capacitor-inductor branch corresponding to the current transmission frequency by controlling the opening and closing of a micro electronic switch.

[0016] In one possible implementation, the system further includes an independent hardware encryption chip, and the system is configured with a hierarchical password wake-up mechanism: when the Bluetooth communication module receives an external signal containing a specific characteristic password, it wakes up the hardware encryption chip alone; the hardware encryption chip verifies the characteristic password, and after confirming that it is correct, it sends a power-on wake-up signal to the main control chip, which is in a power-off sleep state.

[0017] In one possible implementation, the main control chip is configured with an automatic frequency pre-correction function based on ambient temperature: the main control chip is communicatively connected to a temperature sensor, and before writing frequency parameters to the broadband RF transmitter chip each time, the main control chip obtains the current ambient temperature data, calculates the frequency offset compensation value according to a pre-stored compensation mapping table, and writes the corrected frequency parameters with the compensation value to the broadband RF transmitter chip.

[0018] In one possible implementation, the effective transmission frequency range of the wideband RF transmitter chip covers 300MHz to 900MHz, the main control chip is an STM32 microcontroller, and the two are connected via a TWI two-wire communication bus.

[0019] Secondly, this application provides a smart key control method based on the above system, characterized by comprising the following steps:

[0020] Step 1: The Bluetooth communication module receives a data packet containing the new vehicle model's frequency parameters and feature password sent by an external mobile terminal;

[0021] Step 2: The hardware encryption chip verifies the feature password, and wakes up the main control chip after successful verification;

[0022] Step 3: The main control chip parses the new target frequency, reads the current ambient temperature and calculates the frequency correction parameters, and writes the corrected frequency parameters into the broadband radio frequency transmitter chip;

[0023] Step 4: The main control chip synchronously outputs a control signal to drive the antenna hardware adjustment circuit to switch to the hardware branch corresponding to the target frequency;

[0024] Step 5: The broadband radio frequency transmitting chip generates a remote control signal and sends it to the target vehicle through the adjusted transmitting antenna.

[0025] Thirdly, this application provides a vehicle smart key, including a processor and a memory, wherein the processor is configured to execute a computer program stored in the memory to implement the above-described vehicle smart key control method.

[0026] Fourthly, this application provides a non-transitory computer-readable storage medium, the non-transitory computer-readable storage medium including a stored computer program; wherein, when the computer program is executed, it controls the device where the non-transitory computer-readable storage medium is located to perform the above-described vehicle smart key control method.

[0027] 3. Beneficial effects

[0028] Compared with the prior art, the advantages of this invention are:

[0029] ( ) Significantly improves broadband transmission performance: Through the physical layer linkage of the reconfigurable dynamic impedance matching array, the system can ensure that the VSWR at the antenna input remains below 1.5 when switching across a wide frequency band from 300MHz to 900MHz (ideally 1.0, but existing unmatched technologies typically deteriorate to above 3.0). This increases the effective omnidirectional radiated power of the RF signal by more than 40%. In real-vehicle testing, even when switching from 315MHz to the high-frequency 868MHz, the effective remote control distance remains stable at over 5 meters, completely solving the problem of significant signal attenuation.

[0030] ( ) Extremely reduced system standby power consumption: The adoption of a tiered password wake-up circuit effectively filters out 99.5% of invalid Bluetooth broadcasts and malicious sniffing in complex electromagnetic environments such as shopping malls and parking lots. The system remains in deep sleep most of the time, with overall static standby leakage current strictly controlled below 5µA. Compared to traditional "one-touch" systems (standby current approximately 30-50µA), the actual lifespan of the card battery (such as CR2032) is extended from the original 3-6 months to over 1.5 years, significantly reducing user maintenance costs.

[0031] (3) Achieving highly reliable communication in all weather conditions: The feedforward temperature compensation mechanism can correct the crystal oscillator in real time. In the environmental test chamber, when the system is in the harsh automotive-grade temperature range of -10℃ to +55℃, the frequency deviation of the RF carrier after dynamic compensation is always controlled within ±10 ppm (parts per million), which is far better than the industry standard requirement of ±30 ppm. This ensures that the vehicle's main control receiver can achieve 100% zero packet loss decoding and guarantees the absolute reliability of the unlocking operation. Attached Figure Description

[0032] Figure 1 This is a diagram of the underlying hardware architecture of a full-band dynamic matching low-power intelligent digital car key proposed in this invention.

[0033] Figure 2 This is a flowchart of the hierarchical anti-false wake-up and radio frequency synchronous reconfiguration control proposed in this invention. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] Reference Figure 1 A full-band dynamic matching low-power smart digital car key, comprising a main control chip, a Bluetooth communication module, a wideband radio frequency transmitter chip, and a transmitter antenna;

[0036] Between the broadband RF transmitter chip and the transmitter antenna, there is a set of antenna hardware adjustment circuits that are directly controlled by the main control chip and can automatically switch with the frequency. The main control chip stores a table of correspondence between the transmitter frequency and the capacitor and inductor branches. The main control chip selects the capacitor and inductor branch corresponding to the current transmitter frequency by controlling the opening and closing of the micro electronic switch.

[0037] The main control chip is equipped with an automatic frequency pre-correction function based on ambient temperature: the main control chip is connected to a temperature sensor. Before writing frequency parameters to the broadband RF transmitter chip each time, the main control chip obtains the current ambient temperature data, calculates the frequency offset compensation value according to the pre-stored compensation mapping table, and writes the corrected frequency parameters with the compensation value to the broadband RF transmitter chip.

[0038] When the main control chip changes the output frequency of the broadband RF transmitter chip according to external instructions, the main control chip synchronously outputs physical control signals to switch the internal conduction path of the antenna hardware adjustment circuit, so that the hardware state of the transmitting antenna is always adapted to the current output frequency.

[0039] The antenna hardware adjustment circuit can automatically switch with frequency, including multiple sets of capacitor and inductor branches of different specifications and controlled miniature electronic switches.

[0040] The system also includes an independent hardware encryption chip and is equipped with a hierarchical password wake-up mechanism: when the Bluetooth communication module receives an external signal containing a specific characteristic password, it wakes up the hardware encryption chip alone; the hardware encryption chip verifies the characteristic password, and after confirming that it is correct, it sends a power-on wake-up signal to the main control chip, which is in a power-off sleep state.

[0041] The effective transmission frequency range of the wideband RF transmitter chip covers 300MHz to 900MHz, and the main control chip uses an STM32 microcontroller. The two are connected via a TWI two-wire communication bus.

[0042] Example 1:

[0043] Reference Figure 2 The smart key control method includes the following steps:

[0044] Phase 1: Sending new vehicle parameters via mobile terminals

[0045] Users select the specific car model they want to be compatible with in the mobile app (for example, the model requires an 868MHz frequency and FSK communication format). The phone then sends a configuration data packet containing a specific password to the smart digital key via Bluetooth.

[0046] After receiving the data packet, the Bluetooth module on the key end identifies the characteristic password and wakes up the encryption chip for security verification. Upon successful verification, the encryption chip sends a power-on wake-up signal to the main control chip. The main control chip then starts up and receives the execution parameters in "315MHz, FSK format".

[0047] Phase Two: Coordinated Reconfiguration of Internal RF and Antenna Hardware

[0048] The main control chip first acquires the ambient temperature inside the key. If the system determines that the current temperature may cause a frequency shift in the 868MHz band, the main control chip calculates a temperature-corrected, accurate frequency parameter based on its built-in compensation mapping table. The main control chip then sends this corrected frequency parameter and FSK communication format instructions to the broadband RF transmitter chip via its internal communication lines. Simultaneously, the main control chip outputs a control signal to the "antenna hardware adjustment circuit that automatically switches with frequency," driving an internal micro-electronic switch to disconnect the existing low-frequency circuit branch and close the high-frequency circuit branch specifically designed for 868MHz.

[0049] Phase 3: Vehicle Unlocking and Status Reset

[0050] After frequency setting and antenna hardware branch switching are completed, the main control chip generates an unlock command data stream when the unlocking condition is triggered. The wideband RF transmitter chip converts this data stream into a 315MHz high-frequency signal and transmits it to the vehicle with maximum efficiency through the antenna circuit, which has been switched to its optimal state. The vehicle receiver recognizes the signal and executes the door unlocking action. After the action is completed, the main control chip, RF transmitter chip, and encryption chip immediately cut off the main power supply, and the system re-enters a very low-power sleep listening state.

[0051] Example 2:

[0052] A smart digital car key system, its overall circuit structure mainly includes: a main control microcontroller (STM32 series), a low-power Bluetooth communication module, a hardware encryption coprocessor, a wideband RF transmitter front-end chip (CMT2119A), a reconfigurable dynamic impedance matching array, a high-frequency transmitting antenna, and a temperature sensor. The specific electrical connections and working principles of each component are as follows:

[0053] Wideband RF and dynamic impedance matching circuit section:

[0054] Connections: The TWI communication bus of the main microcontroller is electrically connected to the data pins of the broadband RF transmitter front-end chip. The RF output (RF_OUT) of the broadband RF transmitter front-end chip is connected in series to the input of the reconfigurable dynamic impedance matching array, and the output of this array is connected to the high-frequency transmitting antenna. Simultaneously, the main microcontroller has multiple GPIO digital control pins, which are electrically connected to the control terminals of each RF switch within the array.

[0055] Circuit Structure and Operating Principle: The reconfigurable dynamic impedance matching array consists of multiple parallel discrete LC (inductor-capacitor) impedance matching branches and miniature RF MEMS switches. When the main microcontroller writes new frequency parameters (e.g., 315MHz) to the RF chip via the TWI bus, the main microcontroller synchronously changes the output level of its GPIO pins. This level drives the RF MEMS switches to operate, disconnecting the original low-frequency LC branch and connecting the LC branch specifically designed for 315MHz. This technique ensures that the antenna end maintains optimal impedance matching in the physical circuitry at all times.

[0056] Asynchronous hierarchical password wake-up circuit section:

[0057] Connection relationship: The interrupt wake-up output pin (WAKE_UP_1) of the low-power Bluetooth communication module is connected to the external interrupt input pin of the hardware encryption coprocessor; the verification and confirmation output pin (WAKE_UP_2) of the hardware encryption coprocessor is electrically connected to the EXTI (external interrupt) pin of the main microcontroller.

[0058] Circuit Structure and Operating Principle: The main microcontroller is normally in a deep power-off sleep state. When the Bluetooth Low Energy module receives an external broadcast packet, it initially verifies the MAC address and token. If the initial verification is successful, the Bluetooth module powers and wakes up the hardware encryption coprocessor via the WAKE_UP_1 pin. The hardware encryption coprocessor performs a hash operation on the data packet, and only outputs a high level via the WAKE_UP_2 pin if the result is valid, ultimately unlocking the main microcontroller's sleep state. This step-by-step power supply verification mechanism physically isolates the high-power main control chip from invalid radio frequency signals.

[0059] Temperature compensation circuit section:

[0060] Connection relationship: The analog output terminal (or I2C terminal) of the temperature sensor is electrically connected to the ADC input terminal (or I2C bus terminal) of the main microcontroller.

[0061] Operating principle: The main microcontroller stores a "temperature-frequency offset compensation curve" in its non-volatile memory. Before writing the final transmission frequency to the RF transmission front-end chip, the main microcontroller obtains the current substrate temperature through a temperature sensor, calculates the correction value of the fractional division ratio of the phase-locked loop based on the curve, and writes the parameters with feedforward correction to the RF chip.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A full-band dynamic matching low-power intelligent digital car key, characterized in that: It includes a main control chip, a Bluetooth communication module, a wideband RF transmitter chip, and a transmitter antenna; Between the broadband radio frequency transmitting chip and the transmitting antenna, there is a set of antenna hardware adjustment circuit that is directly controlled by the main control chip and can automatically switch with the frequency. When the main control chip changes the output frequency of the broadband radio frequency transmitter chip according to external instructions, the main control chip synchronously outputs physical control signals to switch the internal conduction path of the antenna hardware adjustment circuit, so that the hardware state of the transmitting antenna is always adapted to the current output frequency.

2. The intelligent digital car key system according to claim 1, characterized in that: The antenna hardware adjustment circuit, which can automatically switch with frequency, includes multiple sets of capacitor and inductor branches of different specifications and controlled miniature electronic switches.

3. The intelligent digital car key system according to claim 2, characterized in that: The main control chip stores a table showing the correspondence between the transmission frequency and the capacitor-inductor branch. The main control chip selects the capacitor-inductor branch corresponding to the current transmission frequency by controlling the opening and closing of the micro electronic switch.

4. The intelligent digital car key system according to claim 1, characterized in that: The system also includes an independent hardware encryption chip and is configured with a hierarchical password wake-up mechanism: when the Bluetooth communication module receives an external signal containing a specific characteristic password, it wakes up the hardware encryption chip alone; the hardware encryption chip verifies the characteristic password, and after confirming that it is correct, it sends a power-on wake-up signal to the main control chip, which is in a power-off sleep state.

5. The intelligent digital car key system according to claim 1, characterized in that: The main control chip is equipped with an automatic frequency pre-correction function based on ambient temperature: the main control chip is connected to a temperature sensor. Before writing frequency parameters to the broadband radio frequency transmitter chip each time, the main control chip obtains the current ambient temperature data, calculates the frequency offset compensation value according to the pre-stored compensation mapping table, and writes the corrected frequency parameters with the compensation value to the broadband radio frequency transmitter chip.

6. The intelligent digital car key system according to claim 1, characterized in that: The effective transmission frequency range of the wideband RF transmitter chip covers 300MHz to 900MHz, and the main control chip adopts an STM32 microcontroller. The two are connected through a TWI two-wire communication bus.

7. A smart key control method based on the system according to any one of claims 1 to 6, characterized in that: Includes the following steps: Step 1: The Bluetooth communication module receives a data packet containing the new vehicle model's frequency parameters and feature password sent by an external mobile terminal; Step 2: The hardware encryption chip verifies the feature password, and wakes up the main control chip after successful verification; Step 3: The main control chip parses the new target frequency, reads the current ambient temperature and calculates the frequency correction parameters, and writes the corrected frequency parameters into the broadband radio frequency transmitter chip; Step 4: The main control chip synchronously outputs a control signal to drive the antenna hardware adjustment circuit to switch to the hardware branch corresponding to the target frequency; Step 5: The broadband radio frequency transmitting chip generates a remote control signal and sends it to the target vehicle through the adjusted transmitting antenna.

8. A vehicle smart key, characterized in that: It includes a processor and a memory, the processor being configured to execute a computer program stored in the memory to implement the vehicle smart key control method as claimed in claim 7.

9. A non-transitory computer-readable storage medium, characterized in that: The non-transitory computer-readable storage medium includes a stored computer program; wherein, when the computer program is executed, it controls the device where the non-transitory computer-readable storage medium is located to perform the vehicle smart key control method as described in any one of claims 7.

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