A variable frequency regulation system and method for improving the anti-interference performance of wheel sensor

Abstract

The present invention discloses a variable frequency regulation system and method for improving the anti-interference performance of a wheel sensor, comprising a microcontroller circuit; the microcontroller circuit is respectively connected to a DDS signal generating circuit, a receiving resonance regulating circuit, a receiving signal sampling conversion circuit, a temperature detection circuit, a CAN communication circuit, an EEPROM circuit and an ADC reference circuit; the DDS signal generating circuit is sequentially connected to a power amplifier circuit, a transmitting resonance regulating circuit and a transmitting signal sampling conversion circuit; the output end of the transmitting signal sampling conversion circuit is connected to the microcontroller circuit; and the transmitting resonance regulating circuit is controlled by the microcontroller circuit. The present invention can improve the sensing reliability and anti-interference performance of the wheel sensor to meet the wheel detection requirements under the electromagnetic environment of different projects, and the present invention can adjust the working frequency of the wheel sensor according to the different interference frequencies of each project, so that the wheel sensor has higher flexibility and anti-interference ability.

Description

Technical Field

[0001] The present invention belongs to the technical field of rail transportation, and in particular relates to a variable frequency regulation system and method capable of improving the anti-interference performance of a wheel sensor. Background Art

[0002] At present, the wheel sensors of axle counting equipment are all designed based on the principle of electromagnetic induction. The purpose of detection is achieved through the influence of metal objects such as wheels on the alternating magnetic field. Usually, the signal frequency of the sensor's transmitting coil is fixed and divided into 1 or 2 groups of frequencies. The receiving coil and subsequent signal processing circuit are designed with a corresponding frequency selection function to improve the system's anti-interference ability.

[0003] However, in actual projects, the electromagnetic environment is very complex. The interference source, interference signal frequency, and component size of each project are different. It is very likely that the most serious interference signal harmonic frequency is close to the sensor operating frequency. At this time, the effect of the frequency selection circuit is greatly reduced, resulting in a decrease in the anti-interference performance of the wheel sensor. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a variable frequency regulation system and method that can improve the anti-interference performance of wheel sensors, so as to solve the problem that existing wheel sensors cannot adapt to complex electromagnetic environment interference in different projects due to their fixed operating frequency.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, a variable frequency regulation system and method for improving the anti-interference performance of a wheel sensor includes a microcontroller circuit; the microcontroller circuit is respectively connected to a DDS signal generating circuit, a receiving resonance regulating circuit, a receiving signal sampling conversion circuit, a temperature detecting circuit, a CAN communication circuit, an EEPROM circuit, and an ADC reference circuit;

[0007] The DDS signal generating circuit is connected to the power amplifier circuit, the transmitting resonance regulating circuit and the transmitting signal sampling and converting circuit in sequence; the output end of the transmitting signal sampling and converting circuit is connected to the microcontroller circuit; the transmitting resonance regulating circuit is controlled by the microcontroller circuit;

[0008] The receiving resonance adjustment circuit is respectively connected to the receiving signal processing circuit and the receiving signal sampling conversion circuit; the receiving signal processing circuit is connected to the sensor output signal sampling conversion circuit; the sensor output signal sampling conversion circuit and the receiving signal sampling conversion circuit are both connected to the microcontroller circuit.

[0009] Furthermore, the transmitting resonance adjustment circuit is an LC series resonance circuit; the LC series resonance circuit includes MOSFET tubes Q1, Q2, ..., Qn, capacitors C1, C2, ..., C(n+1) and coil L1; the capacitors C1, C2, ..., C(n+1) are connected in parallel in sequence and then connected in series with the coil L1; the MOSFET tubes Q1, Q1, ..., Qn are respectively arranged on the branches where the capacitors C2, ..., C(n+1) are located.

[0010] Furthermore, the MOSFET tubes Q1, Q2, ..., Qn are used as switches to control the on / off of the branches where the capacitors C2, ..., C(n+1) are located, respectively. A single MOSFET tube has two states: on / off. The MOSFET tubes Q1, Q2, ..., Qn have two n A combination of MOS switches.

[0011] Furthermore, the receiving resonance adjustment circuit is an LC parallel resonance circuit; the LC parallel resonance circuit includes MOSFET tubes Q5, Q6, ..., Q(n+4), capacitors C6, C7, ..., C(n+6) and coil L2; the coil L2 and capacitors C6, C7, ..., C(n+6) are arranged in parallel in sequence; the MOSFET tubes Q5, Q6, ..., Q(n+4) are respectively arranged on the branches where capacitors C7, ..., C(n+6) are located.

[0012] Furthermore, the MOSFET tubes Q5, Q6, ..., Q(n+4) are used as switches to control the on / off of the branches where the capacitors C7, ..., C(n+6) are located. A single MOSFET tube has two states of on / off. Therefore, the MOSFET tubes Q5, Q6, ..., Q(n+4) have 2 n A combination of MOS switches.

[0013] In a second aspect, a method for a variable frequency regulation system capable of improving the anti-interference performance of a wheel sensor comprises the following steps:

[0014] S1, obtaining the spectrum distribution diagram of the interference signal in the space around the wheel sensor. When the interference signal frequency or its higher harmonics are within the 3db bandwidth of the standard operating frequency set by the wheel sensor, and the amplitude of the interference signal frequency component exceeds the specified value, enter S2;

[0015] S2, the microcontroller circuit receives the frequency information transmitted by the wheel sensor through the CAN communication circuit;

[0016] S3, the microcontroller circuit calculates the register control data required by the DDS signal generating circuit according to the received frequency information, and sends it to the DDS signal generating circuit through the SPI interface, and the DDS signal generating circuit generates the required frequency signal;

[0017] S4, the power amplifier circuit amplifies the frequency signal output by the DDS signal generating circuit, drives the two ends of the coil L1 in the transmitting resonance regulating circuit to generate an alternating voltage, and according to the generated alternating voltage, the microcontroller circuit controls the transmitting resonance regulating circuit to adjust the capacitance until the voltage across the coil L1 remains unchanged;

[0018] S5. According to the change of the frequency information in the transmitting resonance adjustment circuit, the microcontroller circuit controls the receiving resonance adjustment circuit to adjust the capacitance until the voltage across the coil L2 in the receiving resonance adjustment circuit remains unchanged;

[0019] S6. The microcontroller circuit sends the frequency information, the DDS signal generating circuit register parameter information, the control information of the MOS switch combination of the transmitting resonance adjustment circuit, and the control information of the MOS switch combination of the receiving resonance adjustment circuit to the EEPROM circuit through the IIC interface for storage, and reports the adjustment success information to the indoor host at the same time.

[0020] Further, the capacitance adjustment of the transmitting resonance adjustment circuit in S4 includes:

[0021] The microcontroller circuit outputs the control signal of the first MOS switch combination, the capacitor corresponding to the first MOS switch combination is connected to the circuit and outputs the control signal, the transmitting signal sampling and conversion circuit converts the voltage of the coil L1 into a DC signal and sends it back to the microcontroller circuit for ADC conversion, if the ADC result meets the specified value range, the capacitance adjustment of the transmitting resonance adjustment circuit is completed;

[0022] If the ADC result does not meet the specified value range, the microcontroller circuit outputs the next MOS switch combination control signal, the capacitor corresponding to the MOS switch combination is connected to the circuit, and the transmission signal sampling and conversion circuit converts the coil L1 voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion, and determines again whether the ADC result meets the specified value range;

[0023] This cycle is repeated until the ADC result corresponding to the selected MOS switch combination meets the specified value range, thereby completing the capacitance adjustment of the transmitting resonant adjustment circuit.

[0024] Further, the microcontroller circuit in S5 controls the receiving resonance adjustment circuit to adjust the capacitance, including:

[0025] The microcontroller circuit outputs a control signal of the first MOS switch combination in the receiving resonance adjustment circuit, the capacitor corresponding to the first MOS switch combination is connected to the circuit, and outputs a control signal, the receiving signal sampling and conversion circuit converts the voltage of the coil L2 into a DC signal and sends it back to the microcontroller circuit for ADC conversion, if the ADC result meets the specified value range, the capacitor adjustment of the receiving resonance adjustment circuit is completed;

[0026] If the ADC result does not meet the specified value range, the microcontroller circuit outputs the control signal of the next MOS switch combination in the receiving resonance adjustment circuit, the capacitor corresponding to the MOS switch combination is connected to the circuit, and the receiving signal sampling and conversion circuit converts the voltage of the coil L2 into a DC signal and sends it back to the microcontroller circuit for ADC conversion, and determines again whether the ADC result meets the specified value range;

[0027] This cycle is repeated until the ADC result corresponding to the selected MOS switch combination meets the specified value range, thereby completing the capacitor adjustment of the receiving resonant adjustment circuit.

[0028] In a third aspect, a method for a variable frequency regulation system capable of improving the anti-interference performance of a wheel sensor according to any one of claims 1 to 5 is characterized in that it comprises the following steps:

[0029] T1. The indoor host sends a calibration command to the wheel sensor through the CAN communication circuit. After receiving the command, the microcontroller circuit performs ADC conversion on the output signal of the sensor output signal sampling and conversion circuit, stores the ADC value in the EEPROM circuit, and reports the calibration operation success information to the indoor host.

[0030] T2, when the outdoor ambient temperature changes and causes the wheel sensor output signal to change by more than 5% of the preset value, the microcontroller circuit sends temperature drift limit information to the indoor host through the CAN communication circuit;

[0031] T3. After receiving the temperature drift exceeding limit information, the indoor host sends a warning signal to the user. The user confirms that the sensor is installed correctly and determines that the temperature exceeds the limit. Then the user operates the indoor host to send a calibration command to the wheel sensor through the CAN communication circuit. The microcontroller circuit receives the calibration command and reads the temperature drift compensation configuration information from the EEPROM circuit. The microcontroller circuit controls and selects the MOS switch combination in the transmitting resonance adjustment circuit until the voltage across the coil L1 in the transmitting resonance adjustment circuit remains unchanged, thereby completing the capacitance adjustment of the transmitting resonance adjustment circuit.

[0032] T4. According to the change of the frequency information in the transmitting resonance adjustment circuit, the microcontroller circuit controls and selects the MOS switch combination in the receiving resonance adjustment circuit until the voltage across the coil L2 in the receiving resonance adjustment circuit remains unchanged, thereby completing the adjustment of the capacitance of the receiving resonance adjustment circuit;

[0033] T5. Perform ADC conversion on the output signal of the sensor output signal sampling and conversion circuit, store the ADC value in the EEPROM circuit, and report the calibration operation success information to the indoor host.

[0034] The frequency conversion regulation system and method for improving the anti-interference performance of a wheel sensor provided by the present invention have the following beneficial effects:

[0035] 1. The present invention can improve the sensing reliability and anti-interference performance of the wheel sensor to adapt to the wheel detection requirements under the electromagnetic environment of different projects. In addition, the present invention can adjust the working frequency of the wheel sensor according to the different interference frequencies of each project, so that the wheel sensor has higher flexibility and anti-interference ability.

[0036] 2. The present invention proposes for the first time a method for changing the working frequency of a wheel sensor and automatically adjusting the resonant frequencies of a transmitting circuit and a receiving circuit, which can greatly improve the anti-interference capability of the wheel sensor.

[0037] 3. The present invention proposes for the first time to add a temperature sensor to the wheel sensor, and utilizes the adjustable capacitance of the transmitting resonance and receiving resonance circuits to achieve temperature compensation of the wheel sensor, thereby improving the adaptability of the wheel sensor to the environment.

[0038] 4. The operating frequency of the wheel sensor of the present invention and the adjustment of automatic temperature compensation are controlled by the indoor host, and the wheel sensor cannot be adjusted autonomously. At the same time, data redundancy check and encryption processing are performed on the communication data between the wheel sensor and the indoor host, thereby ensuring the safety and reliability of the wheel sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a principle block diagram of a frequency conversion regulation system that can improve the anti-interference performance of a wheel sensor.

[0040] Figure 2 This is the DDS signal generating circuit of the present invention.

[0041] Figure 3 This is a schematic diagram of the series resonant regulation circuit of the present invention.

[0042] Figure 4 This is a schematic diagram of the parallel resonance regulation circuit of the present invention.

[0043] Figure 5 It is the main program flow chart of the microcontroller program of the present invention.

[0044] Figure 6 This is a flow chart of initializing the microcontroller program system of the present invention.

[0045] Figure 7 This is a flow chart of the microcontroller controlling the transmission resonant circuit adjustment of the present invention.

[0046] Figure 8 The microcontroller receives the resonant circuit adjustment flow chart of the present invention. DETAILED DESCRIPTION

[0047] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0048] Example 1

[0049] This embodiment provides a variable frequency adjustment system that can improve the anti-interference performance of the wheel sensor. This embodiment can adjust the working frequency of the sensor according to the different interference frequencies of each project, so that the wheel sensor has higher flexibility and anti-interference ability. Figure 1 , which specifically include:

[0050] Microcontroller circuit, DDS signal generating circuit, power amplifier circuit, transmitting resonance regulating circuit, transmitting signal sampling and converting circuit, receiving resonance regulating circuit, receiving signal processing circuit, receiving signal sampling and converting circuit, temperature detecting circuit, CAN communication circuit, EEPROM circuit, ADC reference circuit and sensor output signal sampling and converting circuit.

[0051] The microcontroller circuit is respectively connected with the DDS signal generating circuit, the receiving resonance adjusting circuit, the receiving signal sampling and converting circuit, the temperature detecting circuit, the CAN communication circuit, the EEPROM circuit and the ADC reference circuit.

[0052] The DDS signal generating circuit is connected to the power amplifying circuit, the transmitting resonance regulating circuit and the transmitting signal sampling and converting circuit in sequence; the output end of the transmitting signal sampling and converting circuit is connected to the microcontroller circuit; the transmitting resonance regulating circuit is controlled by the microcontroller circuit;

[0053] The receiving resonance adjustment circuit is respectively connected to the receiving signal processing circuit and the receiving signal sampling conversion circuit; the receiving signal processing circuit is connected to the sensor output signal sampling conversion circuit; the sensor output signal sampling conversion circuit and the receiving signal sampling conversion circuit are both connected to the microcontroller circuit.

[0054] Specifically, each circuit will be described in detail below:

[0055] Microcontroller circuits;

[0056] The microcontroller circuit is used to complete the conversion from analog to digital, the adjustment of the transmission frequency, the resonance adjustment of the transmission circuit, the adjustment of the receiving frequency selection circuit, etc. At the same time, it reads the temperature information, performs logical calculations on all the data, determines the control results of the transmission circuit and the receiving frequency selection circuit, and completes the adjustment of the sensor working frequency according to the command of the host computer.

[0057] In order to reduce the power consumption of the sensor, the microcontroller of this embodiment adopts the STM32L151CCT6 chip with a main frequency of 32MHz, which is multiplied to 168M by an external 8M crystal oscillator. The STM32L151CCT6 adopts STMicroelectronics' ultra-low power consumption technology, with extremely low standby current and operating current. It supports multiple sleep modes and can run in low power consumption mode to improve the energy efficiency of the system. It supports analog interfaces, including 12-bit ADC (analog-to-digital converter) and 12-bit DAC (digital-to-analog converter), which can be used for the input and output of analog signals. It supports hardware encryption and decryption modules, and has multiple memory protection units to protect sensitive data in the memory.

[0058] DDS signal generating circuit;

[0059] The full name of the DDS signal generating circuit is direct digital frequency synthesizer, which is a digital circuit that can generate various waveform signals with high precision and high speed. The DDS signal generating circuit of this embodiment is controlled by a microcontroller circuit and is used to generate a square wave or a sine wave, and its frequency can be controlled and generated according to actual needs.

[0060] Specifically, as a preferred embodiment of this embodiment, refer to Figure 2 The DDS signal generation circuit adopts AD9833, which is a low-power, programmable waveform generator produced by ADI, and can generate sine wave, triangle wave, and square wave output. AD9833 does not require external components, and the output frequency and phase can be programmed by software, which is easy to adjust. The frequency register is 28 bits. When the main frequency clock is 25MHz, the accuracy is 0.1Hz, and when the main frequency clock is 1MHz, the accuracy can reach 0.004Hz. The present invention adopts a 25MHz active crystal oscillator to provide a clock signal to AD9833, and the SPI bus signal line and control line are buffered by 74HC244, and the waveform signal output is shaped by 74ls14.

[0061] Power amplifier circuit;

[0062] The power amplifier circuit amplifies the square wave or sine wave output by the DDS signal generation circuit to drive the transmitting coil to generate an alternating magnetic field.

[0063] The power amplifier circuit uses a totem pole circuit. The voltage amplitude output by the DDS signal generation circuit is 3.3V, which is converted to 12V by the voltage conversion chip and then amplified by a push-pull amplifier circuit composed of MOS. The upper tube of the push-pull circuit is PMOS and the lower tube is NMOS.

[0064] Transmitting resonance regulating circuit;

[0065] The transmitting resonance adjustment circuit is usually an LC resonance circuit, which is divided into a parallel resonance circuit and a series resonance circuit. The inductance L in the circuit remains unchanged, and its switch is controlled by a microcontroller circuit to open or close. Capacitors of different capacitance values ​​are selected to connect to the LC circuit to control the resonance center frequency.

[0066] The transmitting resonance adjustment circuit of this embodiment is LC series resonance, referring to Figure 3 MOSFET tubes Q1, Q2, Q3, Q4 are used as switches to control the on and off of capacitors C2, C3, C4, C5. MOSFET tubes Q1, Q2, Q3, Q4 are controlled by a microcontroller circuit. The capacitance value of capacitor C1 is much larger than that of capacitors C2, C3, C4, C5, and the capacitance value distribution of C2, C3, C4, C5 is increasing. According to the actual needs of the sensor transmitting circuit, the number of capacitors and MOSFET tubes can be increased to achieve the purpose of precise frequency control.

[0067] MOSFET tubes Q1, Q2, Q3, and Q4 are used as switches to control the on and off of the branches where capacitors C2, C3, C4, and C5 are located respectively. A single MOSFET tube has two states of on / off, so MOSFET tubes Q1, Q2, Q3, and Q4 have 16 MOS switch combinations.

[0068] Transmitted signal sampling and conversion circuit;

[0069] The transmitting signal sampling and conversion circuit converts the voltage of the transmitting coil L1 into a DC voltage. It is mainly composed of a rectifier circuit and a filter circuit. The rectifier circuit converts the high-frequency AC signal into a pulsating DC, which is then converted into a smooth DC through a filter circuit and output to the microcontroller circuit.

[0070] Specifically, the transmitting signal sampling and conversion circuit mainly converts the voltage signal at both ends of the transmitting coil into a DC signal for ADC conversion by the microcontroller. It is mainly composed of a resistor divider circuit, a precision rectifier circuit, and an active filter circuit. The transmitting voltage generally has a high amplitude and needs to be attenuated by the resistor divider circuit. It is then converted into a pulsating DC signal by a precision rectifier circuit, and then converted into a smooth DC signal by a second-order low-pass filter composed of an operational amplifier and sent to the microcontroller ADC conversion pin.

[0071] Receiving resonant adjustment circuit;

[0072] The receiving resonance adjustment circuit is usually an LC resonance circuit, which is divided into a parallel resonance circuit and a series resonance circuit. The inductance L in the circuit remains unchanged, and its switch is controlled by a microcontroller circuit to open or close. Capacitors of different capacitance values ​​are selected to connect to the LC loop, thereby controlling the resonance center frequency.

[0073] The receiving resonance adjustment circuit of this embodiment is LC parallel resonance. Figure 4, L2 is the receiving coil, MOSFET tubes Q5, Q6, Q7, Q8 are used as switches to control the on and off of capacitors C6, C7, C8, C9, and MOSFET tubes Q5, Q6, Q7, Q8 are controlled by a microcontroller circuit. The capacitance value of capacitor C10 is much larger than that of capacitors C6, C7, C8, C9, and the capacitance value distribution of C6, C7, C8, C9 is increasing. According to the actual needs of the sensor receiving circuit, the number of capacitors and MOSFET tubes can be increased to achieve the purpose of precise frequency control.

[0074] MOSFET tubes Q5, Q6, Q7, and Q8 are used as switches to control the on / off of the branches where capacitors C7, C8, C9, and C10 are located respectively. A single MOSFET tube has two states of on / off, so MOSFET tubes Q5, Q6, Q7, and Q8 have 16 MOS switch combinations.

[0075] Received signal processing circuit;

[0076] The receiving signal processing circuit converts the received frequency-selected AC signal into a DC current or a switching signal output. Its implementation method is a mature existing technology and is not described in detail in this embodiment.

[0077] Received signal sampling and conversion circuit;

[0078] The received frequency-selected AC signal is converted into a DC voltage, which is mainly composed of a rectifier circuit and a filter circuit. The rectifier circuit converts the high-frequency AC signal into a pulsating DC, which is then converted into a smooth DC through a filter circuit and output to the microcontroller circuit.

[0079] Specifically, the receiving signal sampling and conversion circuit mainly converts the voltage signal at both ends of the receiving coil into a DC signal for the microcontroller to perform ADC conversion. It is mainly composed of a precision rectifier circuit and an active filter circuit. The received voltage generally has a low amplitude and does not need to be attenuated. It is converted into a pulsating DC signal by the precision rectifier circuit, and then converted into a smooth DC signal by a second-order low-pass filter composed of an operational amplifier, and sent to the microcontroller ADC conversion pin.

[0080] Temperature detection circuit

[0081] The temperature detection circuit uses a digital temperature sensor chip to obtain the ambient temperature, and then transmits the temperature to the microcontroller in communication mode. The temperature detection circuit uses a digital temperature sensor chip LM75A, which is an industry-standard digital temperature sensor with an integrated Σ-Δ analog-to-digital converter (ADC) and I2C interface. LM75A provides 9-bit digital temperature readings with a temperature range of -55℃ to 125℃, and communicates with the microcontroller through the I2C interface.

[0082] CAN communication circuit;

[0083] The CAN communication circuit uses a CAN controller chip to complete the communication with the indoor host. The CAN communication circuit uses ISO1050DWR as a CAN repeater, which complies with the ISO11898-2 standard and provides electrical isolation of up to 5000VRMS to prevent noise current from interfering with sensitive circuits. It has the characteristics of high integration, high-speed transmission, safe isolation, wide operating temperature range and low power consumption design. The CAN bus output is connected in series with a 600R impedance inductor, and TVS is used for protection between lines and line ground. The model is P6SMB6.8CA. At the same time, a 120R resistor is connected in parallel between the lines for impedance matching. Then CANH and CANL are connected in series with fuses, and their model is 1206L050.

[0084] The wheel sensor communicates with the indoor host via CAN. Considering that the wheel sensor may be far away from the indoor host, low-speed communication is selected, and the CAN communication baud rate is 5Kbps. The software protocol is designed as a private protocol, and the communication data uses CRC32 redundancy check to ensure the correctness of the data.

[0085] Since the adjustment of the working frequency of the wheel sensor is very critical and important, in order to avoid malicious modification and misoperation that may cause frequency changes, the AES encryption algorithm is used to encrypt the CAN communication data frame. AES, or Advanced Encryption Standard, is a symmetric key encryption algorithm that is one of the most common and popular technical solutions in the field of cryptography. The basis of AES is a block cipher that uses a 128-bit block size and a 128, 192, or 256-bit key to encrypt data. AES256 is the standard version with a 256-bit key. It is widely regarded as the most secure, commonly used digital cryptography standard and is often used for the most secure end-to-end encrypted communications.

[0086] EEPROM circuit;

[0087] The EEPROM circuit is an electrically erasable programmable read-only memory used to store expected values ​​and threshold information. The EEPROM circuit uses the memory chip SL24C64D, which has an operating voltage range from 1.8V to 5.5V, and is highly flexible to meet the needs of different power supply environments. The advantage of large-capacity storage is obvious, and the 64Kbit capacity is sufficient to cope with various situations that require large amounts of storage, such as detailed log records and critical firmware storage. The I2C bus is used to communicate between the SL24C64D and the microcontroller circuit.

[0088] ADC reference circuit;

[0089] The ADC reference circuit is used to generate an accurate reference voltage and provide a stable voltage for the ADC conversion circuit. The ADC reference circuit uses the voltage reference chip REF3030AIDBZR, which is packaged in SOT-23 and has the characteristics of precision, low power consumption, and low voltage drop. Its high precision, low noise, low temperature drift, and high stability make it suitable for a variety of applications. The output voltage of REF3030AIDBZR is 3.0V, and the output pin is connected to the ground in parallel with a 0.1uF capacitor for decoupling, and then sent to the microcontroller ADC reference power input pin.

[0090] Sensor output signal sampling and conversion circuit;

[0091] The sensor output signal sampling and conversion circuit converts the output signal of the receiving signal processing circuit into a signal suitable for ADC conversion of the microcontroller circuit. If the receiving signal processing circuit outputs a current signal, the sensor output signal sampling and conversion circuit converts the current signal into a DC voltage signal. If the receiving signal processing circuit outputs an AC voltage signal, the sensor output signal sampling and conversion circuit converts the signal into a DC voltage signal, and finally outputs it to the ADC conversion pin of the microcontroller circuit.

[0092] The transmitting resonance adjustment circuit and the receiving resonance adjustment circuit of this embodiment are both LC resonances, and the calculation formula of the resonance center frequency f0 is:

[0093]

[0094] Where L is the inductance, unit is H, and C is the capacitance, unit is F.

[0095] refer to Figure 3 , the transmitting resonance adjustment circuit is LC series resonance, the inductance of coil L1 is fixed, there are 5 capacitors, of which C1 is fixed, C2 is controlled by Q1, C3 is controlled by Q2, C4 is controlled by Q3, C5 is controlled by Q4, Q1, Q2, Q3, Q4 are used as switches, the state is on / off, because there are 4 MOS tubes, so there are 16 different switch combinations, see Table 1 below:

[0096] Table 1 MOS switch combination table of transmitting resonance regulation circuit

[0097]

[0098] Since C1, C2, C3, C4, and C5 are in parallel, the total capacitance value C is calculated as follows:

[0099] C=C1+C2+C3+C4+C5 (Formula 2)

[0100] According to Table 1, there are 16 MOS switch combinations, and there are also 16 corresponding combinations of capacitors C2, C3, C4, and C5. The minimum total capacitance value is when Q1, Q2, Q3, and Q4 are turned off at the same time, calculated as follows:

[0101] C min =C1 (Formula 3)

[0102] The maximum total capacitance value is when Q1, Q2, Q3, and Q4 are turned on at the same time, and the calculation is as follows:

[0103] C max =C1+C2+C3+C4+C5 (Formula 4)

[0104] According to formula 1, the minimum value of the resonant center frequency f is calculated as:

[0105]

[0106] The maximum value of the resonant center frequency is calculated as:

[0107]

[0108] Therefore, the adjustment range of the transmitting resonant center frequency f0 is:

[0109] f min <f0<f max (Formula 7)

[0110] Assuming L1 = 10uH, C1 = 2000pF, C2 = 220pF, C3 = 100pF, C4 = 47pF, C5 = 30pF, then according to formula 3, the minimum total capacitance value is C min =2000pF, according to formula 4, the maximum total capacitance value is C max =2297pF; According to formula 5, the minimum value of the transmitting resonant center frequency is f min =1061.03kHz, the maximum value of the transmitting resonance center frequency is f max =1125.4kHz, the adjustment range of the transmitting resonant center frequency f0 is: 1061.03~1125.4kHz, see Table 2 below for details.

[0111] Table 2 Transmitter resonance adjustment circuit center frequency calculation table

[0112]

[0113]

[0114] The receiving resonance adjustment circuit and the transmitting resonance adjustment circuit of this embodiment have the same principles, which will not be described in detail here.

[0115] The amplitude-frequency characteristics of the series and parallel resonant circuits of this embodiment are:

[0116] Since the DC resistance of the inductor L1 is not zero, the LC resonant circuit is actually equivalent to an RLC circuit. The RLC circuit usually behaves as a second-order system under an AC signal, and its characteristics depend on the values ​​of the resistance R, the inductance L and the capacitance C, as well as the frequency ω of the input signal.

[0117] In a series RLC circuit, the total impedance Z can be expressed as:

[0118]

[0119] Where j is an imaginary unit, satisfying j 2 =-1.

[0120] The amplitude-frequency characteristics of the circuit focus on the impedance modulus, that is:

[0121]

[0122] In a parallel RLC circuit, the total admittance is the sum of the three admittances of resistance, capacitance and inductance, which can be expressed as:

[0123]

[0124] The impedance of parallel resonance is the derivative of admittance and can be expressed as:

[0125]

[0126] The modulus of impedance |Z| can be expressed as:

[0127]

[0128] Since the modulus of the impedance of the RLC circuit is affected by the values ​​of the resistor R, inductor L and capacitor C, as well as the frequency ω of the signal, in this example it is assumed that the resistor R and the inductor L remain unchanged, then the modulus of the impedance of the RLC circuit is only affected by the value of the capacitor C and the frequency ω of the input signal, that is to say, if the value of the capacitor C and the frequency ω of the input signal are changed, the modulus of the impedance of the RLC circuit can be changed, and the modulus of the impedance will affect the change of the circuit current, and ultimately affect the change of the voltage amplitude across the inductor coil.

[0129] Based on the above theoretical explanation, in this example, due to the change in the input signal frequency (the new frequency issued by the technician), the impedance of the RLC series circuit and the parallel circuit changes, which affects the change in the voltage amplitude at both ends of the inductor. Usually, when designing a sensor, it is necessary to keep the voltage amplitude at both ends of the inductor stable. Since the signal frequency ω, resistance R, and inductance L remain unchanged at this time, the circuit impedance can be adjusted by changing the capacitance value C of the resonant circuit so that the voltage amplitude at both ends of the inductor remains unchanged after the signal frequency changes.

[0130] The working principle of a frequency conversion regulation system that can improve the anti-interference performance of a wheel sensor in this embodiment is as follows:

[0131] When the operating frequency of the sensor needs to be changed, the maintenance personnel operate the host in the room to send the frequency parameters that need to be adjusted to the wheel sensor. The microcontroller circuit receives the information through the CAN communication circuit, starts frequency adjustment, controls the DDS signal generating circuit to generate a new frequency signal, and performs power amplification through the power amplifier circuit. Then the microcontroller circuit controls the on and off of the field effect tube in the transmitting resonance adjustment circuit. At the same time, the transmitting signal sampling and conversion circuit converts the transmitting coil voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion. This process starts from MOS switch combination 1. When the transmitting coil voltage corresponding to a certain switch combination meets the preset value, the microcontroller circuit stops the test of the field effect tube switch. At this time, the transmitting resonance adjustment circuit completes the adjustment.

[0132] Then the microcontroller circuit controls the on and off of the field effect tube in the receiving resonance adjustment circuit. At the same time, the receiving signal sampling and conversion circuit converts the transmitting coil voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion. This process starts from MOS switch combination 1. When the receiving coil voltage corresponding to a certain switch combination meets the preset value, the microcontroller circuit stops the test of the field effect tube switch. At this time, the receiving resonance adjustment circuit completes the adjustment.

[0133] When the above process is completed, the microcontroller circuit sends the frequency information, DDS signal generating circuit parameter information, the control information of the field effect transistor switch of the transmitting resonance adjustment circuit, and the control information of the field effect transistor switch of the receiving frequency selection adjustment circuit to the EEPROM circuit through the IIC interface for storage.

[0134] Example 2

[0135] This embodiment provides a frequency conversion adjustment method that can improve the anti-interference performance of the wheel sensor based on embodiment 1, referring to Figures 5 to 8 , which specifically includes the following steps:

[0136] S1. During the joint commissioning and testing of station equipment, the technical personnel use a spectrum analyzer to monitor the spatial interference signal near the wheel sensor and obtain the spectrum distribution diagram of the interference signal in the space around the wheel sensor;

[0137] If the interference signal frequency or its higher harmonics are outside the 3db bandwidth of the standard operating frequency set by the wheel sensor at the factory, and the amplitude of the interference signal frequency component does not exceed the specified value, the frequency of the wheel sensor does not need to be adjusted by frequency conversion, and the standard operating frequency set by the sensor at the factory is still maintained;

[0138] When the interference signal frequency or its higher harmonics are within the 3db bandwidth of the standard operating frequency set by the wheel sensor, and the amplitude of the interference signal frequency component exceeds the specified value, the technicians shall determine the required frequency value based on the interference signal spectrum diagram and the sensor frequency adjustable range, and enter S2;

[0139] S2. After obtaining the user's consent, the technician uses a special tool to connect to the indoor host debugging interface, and sends the frequency information to the wheel sensor through the CAN communication circuit. After the microcontroller circuit receives the information through the CAN communication circuit, it starts to start the frequency adjustment;

[0140] S3, the microcontroller circuit calculates the register control data required by the DDS signal generating circuit according to the received frequency information, and sends it to the DDS signal generating circuit through the SPI interface, and the DDS signal generating circuit generates the required frequency signal;

[0141] S4, the power amplifier circuit amplifies the frequency signal output by the DDS signal generating circuit, and drives the two ends of the coil L1 in the transmitting resonance regulating circuit to generate an alternating voltage. According to the generated alternating voltage, it can be known from Formula 9 in Example 1 that the frequency of the input signal will cause the voltage across the two ends of the inductor to change (increase or decrease). In order to keep the voltage across the two ends of the inductor unchanged, the value of the capacitor C needs to be adjusted. Based on this, the microcontroller circuit controls the transmitting resonance regulating circuit to adjust the capacitance until the voltage across the two ends of the coil L1 remains unchanged, which specifically includes the following contents:

[0142] The microcontroller circuit controls the on and off of the MOS tubes Q1, Q2, Q3, and Q4 in the transmitting resonance adjustment circuit, connects C1, C2, C3, and C4 to the circuit, and outputs a control signal of the first MOS switch combination according to Table 1 in Example 1. The capacitor corresponding to the first MOS switch combination is connected to the circuit and outputs a control signal. The transmitting signal sampling and conversion circuit converts the voltage of the coil L1 into a DC signal and sends it back to the microcontroller circuit for ADC conversion. If the ADC result meets the specified value range, the capacitance adjustment of the transmitting resonance adjustment circuit is completed.

[0143] If the ADC result does not meet the specified value range, the microcontroller circuit outputs the next MOS switch combination control signal, the capacitor corresponding to the MOS switch combination is connected to the circuit, and the transmission signal sampling and conversion circuit converts the coil L1 voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion, and determines again whether the ADC result meets the specified value range;

[0144] This cycle is repeated until the ADC result corresponding to the selected MOS switch combination meets the specified value range, thereby completing the capacitance adjustment of the transmitting resonant adjustment circuit.

[0145] S5. According to the change of frequency information in the transmitting resonance adjustment circuit and the RLC amplitude-frequency characteristic curve, the voltage across the receiving coil must change (increase or decrease). In order to keep the voltage across the inductor coil unchanged, the value of the capacitor C needs to be adjusted. Based on this, the microcontroller circuit controls the receiving resonance adjustment circuit to adjust the capacitance until the voltage across the coil L2 in the receiving resonance adjustment circuit remains unchanged. Specifically, the following contents are included:

[0146] The microcontroller circuit controls the on and off of MOS tubes Q5, Q6, Q7, and Q8 in the receiving resonance adjustment circuit, connects C7, C8, C9, and C10 to the circuit, outputs the control signal of the first MOS switch combination in the receiving resonance adjustment circuit, and the capacitor corresponding to the first MOS switch combination is connected to the circuit and outputs the control signal. The receiving signal sampling and conversion circuit converts the voltage of the coil L2 into a DC signal and sends it back to the microcontroller circuit for ADC conversion. If the ADC result meets the specified value range, the capacitor adjustment of the receiving resonance adjustment circuit is completed;

[0147] If the ADC result does not meet the specified value range, the microcontroller circuit outputs the control signal of the next MOS switch combination in the receiving resonance adjustment circuit, the capacitor corresponding to the MOS switch combination is connected to the circuit, and the receiving signal sampling and conversion circuit converts the voltage of the coil L2 into a DC signal and sends it back to the microcontroller circuit for ADC conversion, and determines again whether the ADC result meets the specified value range;

[0148] This cycle is repeated until the ADC result corresponding to the selected MOS switch combination meets the specified value range, thereby completing the capacitor adjustment of the receiving resonant adjustment circuit.

[0149] S6. The microcontroller circuit sends the frequency information, the DDS signal generating circuit register parameter information, the control information of the MOS switch combination of the transmitting resonance adjustment circuit, and the control information of the MOS switch combination of the receiving resonance adjustment circuit to the EEPROM circuit through the IIC interface for storage, and reports the adjustment success information to the indoor host at the same time.

[0150] Example 3

[0151] This embodiment is based on Embodiment 1 and is used for temperature compensation adjustment of a wheel sensor. Specifically, a frequency conversion adjustment method is provided to improve the anti-interference performance of the wheel sensor. Figures 5 to 8 , which comprises the following steps:

[0152] T1. After the wheel sensor is installed and debugged for the first time, the user operates the indoor host to send a calibration command to the wheel sensor through the CAN communication circuit. After receiving the command, the microcontroller circuit performs ADC conversion on the output signal of the sensor output signal sampling and conversion circuit, stores the ADC value in the EEPROM circuit, and reports the calibration operation success information to the indoor host;

[0153] T2. When the outdoor ambient temperature changes and causes the wheel sensor output signal to change by more than 5% of the preset value, that is, |V1-V0| / V0*100%>5%, V1 is the real-time value of the output signal of the sensor output signal sampling and conversion circuit, and V0 is the value of the output signal of the sensor output signal sampling and conversion circuit during the calibration operation, the microcontroller circuit sends the temperature drift exceeding limit information to the indoor host through the CAN communication circuit;

[0154] T3. After the indoor host receives the temperature drift exceeding limit information, it sends a warning signal to the user. The user confirms that the sensor is installed correctly and determines that the temperature exceeds the limit. Then the user operates the indoor host to send a calibration command to the wheel sensor through the CAN communication circuit. The microcontroller circuit receives the calibration command and reads the temperature drift compensation configuration information from the EEPROM circuit. The microcontroller circuit controls the on and off of the MOS tubes Q1, Q2, Q3, and Q4 in the transmitting resonance adjustment circuit, and connects C1, C2, C3, and C4 to the circuit. According to Table 1, the microcontroller circuit starts to output the control signal from the MOS switch combination 1. The transmitting signal sampling and conversion circuit converts the transmitting coil voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion. If the ADC result meets the specified value range, the transmitting resonance circuit adjustment is completed;

[0155] If the ADC result does not meet the specified value range, the microcontroller circuit outputs the MOS switch combination 2 control signal, and the transmitting signal sampling and conversion circuit converts the transmitting coil voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion, and then determines again whether the ADC result meets the specified value range, and repeats this cycle until a MOS switch combination that meets the requirements is found, and the adjustment of the transmitting resonant circuit is completed;

[0156] T4, the microcontroller circuit controls the on and off of the MOS tubes Q5, Q6, Q7, and Q8 in the receiving resonance adjustment circuit, and connects C7, C8, C9, and C10 to the circuit. The microcontroller circuit starts to output the control signal from MOS switch combination 1, and the receiving signal sampling and conversion circuit converts the receiving coil voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion. If the ADC result meets the specified value range, the adjustment of the receiving resonance circuit is completed. If the ADC result does not meet the specified value range, the microcontroller circuit outputs the MOS switch combination 2 control signal, and the transmitting signal sampling and conversion circuit converts the receiving coil voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion. Then, it is determined again whether the ADC result meets the specified value range. This cycle is repeated until a MOS switch combination that meets the requirements is found, and the adjustment of the receiving resonance adjustment circuit is completed.

[0157] T5. Perform ADC conversion on the output signal of the sensor output signal sampling and conversion circuit, store the ADC value in the EEPROM circuit, and report the calibration operation success information to the indoor host.

[0158] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A variable frequency regulation system capable of improving the anti-interference performance of a wheel sensor, characterized in that: It includes a microcontroller circuit; the microcontroller circuit is respectively connected to a DDS signal generating circuit, a receiving resonance adjusting circuit, a receiving signal sampling and converting circuit, a temperature detecting circuit, a CAN communication circuit, an EEPROM circuit and an ADC reference circuit; The DDS signal generating circuit is connected to the power amplifier circuit, the transmitting resonance regulating circuit and the transmitting signal sampling and converting circuit in sequence; the output end of the transmitting signal sampling and converting circuit is connected to the microcontroller circuit; the transmitting resonance regulating circuit is controlled by the microcontroller circuit; The receiving resonance adjustment circuit is respectively connected to the receiving signal processing circuit and the receiving signal sampling conversion circuit; the receiving signal processing circuit is connected to the sensor output signal sampling conversion circuit; the sensor output signal sampling conversion circuit and the receiving signal sampling conversion circuit are both connected to the microcontroller circuit.

2. The frequency conversion regulation system and method for improving the anti-interference performance of the wheel sensor according to claim 1, characterized in that: The transmitting resonance adjustment circuit is an LC series resonance circuit; the LC series resonance circuit includes MOSFET tubes Q1, Q2..., Qn, capacitors C1, C2,..., C(n+1) and coil L1; the capacitors C1, C2,..., C(n+1) are connected in parallel in sequence and then connected in series with the coil L1; the MOSFET tubes Q1, Q1,..., Qn are respectively arranged on the branches where the capacitors C2,..., C(n+1) are located.

3. The frequency conversion regulation system and method for improving the anti-interference performance of the wheel sensor according to claim 2, characterized in that: The MOSFET tubes Q1, Q2, ..., Qn are used as switches to control the on and off of the branches where the capacitors C2, ..., C(n+1) are located. A single MOSFET tube has two states: on / off. The MOSFET tubes Q1, Q2, ..., Qn have two n A combination of MOS switches.

4. The frequency conversion regulation system and method for improving the anti-interference performance of a wheel sensor according to claim 1, characterized in that: The receiving resonance adjustment circuit is an LC parallel resonance circuit; the LC parallel resonance circuit includes MOSFET tubes Q5, Q6, ..., Q(n+4), capacitors C6, C7, ..., C(n+6) and coil L2; the coil L2 and capacitors C6, C7, ..., C(n+6) are arranged in parallel in sequence; the MOSFET tubes Q5, Q6, ..., Q(n+4) are respectively arranged on the branches where capacitors C7, ..., C(n+6) are located.

5. The frequency conversion regulation system and method for improving the anti-interference performance of the wheel sensor according to claim 4, characterized in that: The MOSFET tubes Q5, Q6, ..., Q(n+4) are used as switches to control the on and off of the branches where the capacitors C7, ..., C(n+6) are located. A single MOSFET tube has two states of on / off. Therefore, the MOSFET tubes Q5, Q6, ..., Q(n+4) have 2 n A combination of MOS switches.

6. A method for a variable frequency regulation system capable of improving the anti-interference performance of a wheel sensor according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, obtaining the spectrum distribution diagram of the interference signal in the space around the wheel sensor. When the interference signal frequency or its higher harmonics are within the 3db bandwidth of the standard operating frequency set by the wheel sensor, and the amplitude of the interference signal frequency component exceeds the specified value, enter S2; S2, the microcontroller circuit receives the frequency information transmitted by the wheel sensor through the CAN communication circuit; S3, the microcontroller circuit calculates the register control data required by the DDS signal generating circuit according to the received frequency information, and sends it to the DDS signal generating circuit through the SPI interface, and the DDS signal generating circuit generates the required frequency signal; S4, the power amplifier circuit amplifies the frequency signal output by the DDS signal generating circuit, drives the two ends of the coil L1 in the transmitting resonance regulating circuit to generate an alternating voltage, and according to the generated alternating voltage, the microcontroller circuit controls the transmitting resonance regulating circuit to adjust the capacitance until the voltage across the coil L1 remains unchanged; S5. According to the change of the frequency information in the transmitting resonance adjustment circuit, the microcontroller circuit controls the receiving resonance adjustment circuit to adjust the capacitance until the voltage across the coil L2 in the receiving resonance adjustment circuit remains unchanged; S6. The microcontroller circuit sends the frequency information, the DDS signal generating circuit register parameter information, the control information of the MOS switch combination of the transmitting resonance adjustment circuit, and the control information of the MOS switch combination of the receiving resonance adjustment circuit to the EEPROM circuit through the IIC interface for storage, and reports the adjustment success information to the indoor host at the same time.

7. The frequency conversion adjustment method for improving the anti-interference performance of the wheel sensor according to claim 6, characterized in that: The capacitance adjustment of the transmitting resonance adjustment circuit in S4 includes: The microcontroller circuit outputs the control signal of the first MOS switch combination, the capacitor corresponding to the first MOS switch combination is connected to the circuit and outputs the control signal, the transmitting signal sampling and conversion circuit converts the voltage of the coil L1 into a DC signal and sends it back to the microcontroller circuit for ADC conversion, if the ADC result meets the specified value range, the capacitance adjustment of the transmitting resonance adjustment circuit is completed; If the ADC result does not meet the specified value range, the microcontroller circuit outputs the next MOS switch combination control signal, the capacitor corresponding to the MOS switch combination is connected to the circuit, and the transmission signal sampling and conversion circuit converts the coil L1 voltage into a DC signal and sends it back to the microcontroller circuit for ADC conversion, and determines again whether the ADC result meets the specified value range; This cycle is repeated until the ADC result corresponding to the selected MOS switch combination meets the specified value range, thereby completing the capacitance adjustment of the transmitting resonant adjustment circuit.

8. The frequency conversion adjustment method for improving the anti-interference performance of a wheel sensor according to claim 6, characterized in that: The microcontroller circuit in S5 controls the receiving resonant adjustment circuit to adjust the capacitance, including: The microcontroller circuit outputs a control signal of the first MOS switch combination in the receiving resonance adjustment circuit, the capacitor corresponding to the first MOS switch combination is connected to the circuit, and outputs a control signal, the receiving signal sampling and conversion circuit converts the voltage of the coil L2 into a DC signal and sends it back to the microcontroller circuit for ADC conversion, if the ADC result meets the specified value range, the capacitor adjustment of the receiving resonance adjustment circuit is completed; If the ADC result does not meet the specified value range, the microcontroller circuit outputs the control signal of the next MOS switch combination in the receiving resonance adjustment circuit, the capacitor corresponding to the MOS switch combination is connected to the circuit, and the receiving signal sampling and conversion circuit converts the voltage of the coil L2 into a DC signal and sends it back to the microcontroller circuit for ADC conversion, and determines again whether the ADC result meets the specified value range; This cycle is repeated until the ADC result corresponding to the selected MOS switch combination meets the specified value range, thereby completing the capacitor adjustment of the receiving resonant adjustment circuit.

9. A method for a variable frequency regulation system capable of improving the anti-interference performance of a wheel sensor according to any one of claims 1 to 5, characterized in that: The following steps are involved: T1. The indoor host sends a calibration command to the wheel sensor through the CAN communication circuit. After receiving the command, the microcontroller circuit performs ADC conversion on the output signal of the sensor output signal sampling and conversion circuit, stores the ADC value in the EEPROM circuit, and reports the calibration operation success information to the indoor host. T2, when the outdoor ambient temperature changes and causes the wheel sensor output signal to change by more than 5% of the preset value, the microcontroller circuit sends temperature drift limit information to the indoor host through the CAN communication circuit; T3. After receiving the temperature drift exceeding limit information, the indoor host sends a warning signal to the user. The user confirms that the sensor is installed correctly and determines that the temperature exceeds the limit. Then the user operates the indoor host to send a calibration command to the wheel sensor through the CAN communication circuit. The microcontroller circuit receives the calibration command and reads the temperature drift compensation configuration information from the EEPROM circuit. The microcontroller circuit controls and selects the MOS switch combination in the transmitting resonance adjustment circuit until the voltage across the coil L1 in the transmitting resonance adjustment circuit remains unchanged, thereby completing the capacitance adjustment of the transmitting resonance adjustment circuit. T4. According to the change of the frequency information in the transmitting resonance adjustment circuit, the microcontroller circuit controls and selects the MOS switch combination in the receiving resonance adjustment circuit until the voltage across the coil L2 in the receiving resonance adjustment circuit remains unchanged, thereby completing the adjustment of the capacitance of the receiving resonance adjustment circuit; T5. Perform ADC conversion on the output signal of the sensor output signal sampling and conversion circuit, store the ADC value in the EEPROM circuit, and report the calibration operation success information to the indoor host.

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