Detection device based on standing-wave ratio bridge

Abstract

The utility model provides a detection device based on a standing-wave ratio bridge. The detection device comprises a standing-wave ratio bridge module, a signal processing module, a control module, an upper computer and a power supply module, the standing-wave ratio bridge module comprises an unbalanced Wheatstone bridge unit and a diode broadband detection unit; the signal processing module comprises a filtering unit and a signal amplification unit; the control module comprises a signal generation unit, a main control unit and a communication unit; the standing-wave ratio bridge module, the signal processing module, the control module and the upper computer are respectively connected with the power supply module. The signal generation unit generates a frequency signal, the frequency signal is coupled with the LC sensor after being processed, four scalar voltages are output through the standing-wave ratio bridge, an impedance real part is calculated after AD sampling, and the impedance real part is sent to an upper computer through the communication unit. The system switches the frequency band, the measurement is repeated until the full frequency band is completed, the upper computer draws an impedance real part curve, and the frequency corresponding to the maximum value of the impedance real part is the resonant frequency of the sensor.

Description

Technical Field:

[0001] The utility model belongs to the technical field of sensors, and relates to a readout detection device for an LC wireless passive sensor. Background Art:

[0002] LC passive wireless sensors have shown excellent application potential in harsh environments due to their small size, low power consumption, long service life, and strong adaptability. Such sensors achieve wireless reading through inductive coupling via a resonant circuit composed of an inductor and a capacitor, and their simple structural design enables them to work effectively under conditions such as high temperature, high pressure, airtightness, and rotation. However, current research on LC passive wireless sensors mainly focuses on the sensors themselves, and the methods for reading the resonant frequency are relatively single.

[0003] In different complex environments, the influence of noise signals varies with environmental changes and is independent of frequency. For example, it is affected by power frequency noise. If the sensor is exposed to air without metal shielding measures, the influence of power frequency noise is inevitable. In a strong noise environment, weak sensor signals may be submerged, which poses a huge challenge to improving signal detection sensitivity and environmental adaptability. Therefore, the selection of the reading method and the design of the reading circuit are crucial for the measurement performance of the sensing system. When designing the reading circuit, it must be ensured that it can accurately, sensitively, and quickly capture the changes of the sensor, which requires meeting strict standards in terms of accuracy, sensitivity, resolution, and detection time, with accuracy being particularly core.

[0004] Currently, due to the mutual inductance effect, traditional technologies cause deviations in the resonant frequency when reading the position. Existing reading technologies mainly rely on large and costly impedance analyzers and network analyzers, making them difficult to be applied in industrial applications, data recording, and other scenarios. Therefore, it is necessary to optimize the reading detection method and simplify the circuit design to minimize the interference of the reading position on the signal and reduce the volume of the reading circuit while ensuring the reading accuracy of the sensor. Summary of the Utility Model:

[0005] The detection device based on a standing wave ratio bridge of the utility model has a simple structure, which enables the reading circuit not to cause resonant frequency deviation at different reading positions, and at the same time reads the accurate resonant frequency in real time, quickly, and with low power consumption, and reduces the volume of the reading circuit.

[0006] The utility model provides a detection device based on a standing wave ratio bridge, which includes a standing wave ratio bridge module, a signal processing module, a control module, a host computer, and a power supply module; the standing wave ratio bridge module includes an unbalanced Wheatstone bridge unit and a diode broadband detection unit; the signal processing module includes a filtering unit and a signal amplification unit; the control module includes a signal generation unit, a main control unit, and a communication unit; the standing wave ratio bridge module, the signal processing module, the control module, and the host computer are respectively connected to the power supply module.

[0007] Optionally, the unbalanced Wheatstone bridge unit includes a first resistor, a second resistor, a third resistor, and a reading coil.

[0008] Optionally, the first resistor, the second resistor, and the third resistor have equal resistance values.

[0009] Optionally, the diode broadband detection unit circuit includes a detection diode of model HSCH-9162.

[0010] Optionally, the reading coil is a planar weakly coupled spiral inductor made of copper.

[0011] Optionally, the main control unit includes an STM32 main control chip.

[0012] Optionally, the signal generation unit includes a signal generator of model AD9850.

[0013] Optionally, the filtering unit includes a low-pass filter.

[0014] Optionally, the signal amplification unit includes an operational amplifier.

[0015] Optionally, the communication unit includes a communication chip of model ESP32. Description of the drawings:

[0016] Figure 1 is a schematic diagram of a detection device based on a standing wave ratio bridge;

[0017] Figure 2 is the circuit diagram of the standing wave ratio bridge;

[0018] Figure 3 is a schematic diagram of a detection process based on a standing wave ratio bridge.

[0019] Description of the reference numerals:

[0020] 1 is the host computer, 2 is the control module, 21 is the communication unit, 22 is the main control unit, 23 is the signal generation unit, 3 is the signal processing module, 31 is the signal amplification unit, 32 is the filtering unit, 4 is the standing wave ratio bridge module, and 5 is the power supply module. 41 is the unbalanced Wheatstone bridge unit, 42 is the diode broadband detection unit, 411 is the reading coil, 412 is the first resistor, 413 is the second resistor, and 414 is the third resistor. Specific implementation mode:

[0021] The embodiments of the present invention will be described in detail below, and the examples of the embodiments are shown in the drawings.

[0022] The detection device based on the standing wave ratio bridge of the present invention has a simple structure, can realize that the resonance frequency does not shift at different reading positions of the reading circuit, and at the same time reads the accurate resonance frequency in real time, quickly, with low power consumption and reduces the volume of the reading circuit.

[0023] The present invention provides a detection device based on a standing wave ratio bridge, including a standing wave ratio bridge module 4, a signal processing module 3, a control module 2, a host computer 1, and a power supply module 5; the standing wave ratio bridge module 4 includes an unbalanced Wheatstone bridge unit 41 and a diode broadband detection unit 42; the signal processing module 3 includes a filtering unit 32 and a signal amplification unit 31; the control module 2 includes a signal generation unit 23, a main control unit 22, and a communication unit 21; the standing wave ratio bridge module 4, the signal processing module 3, the control module 2, and the host computer 1 are respectively connected to the power supply module 5. As Figure 1 shown.

[0024] The LC sensor is affected by the mutual coupling effect, and the reading distance affects the coupling coefficient of the sensor. The change of the coupling coefficient will cause the resonance frequency of the LC sensor to shift, seriously affecting the reliability of the reading signal of the reading circuit. The present invention adopts a reading method of reading the real part impedance value of the sensor. The real part impedance value of the sensor is not affected by the coupling coefficient and will not cause the resonance frequency of the sensor to shift, improving the reliability of the reading signal of the reading circuit.

[0025] In order to accurately and quickly read the real - part impedance value of the sensor and enhance the reliability of the reading signal of the reading circuit. Preferably, optionally, the unbalanced Wheatstone bridge unit 41 includes a first resistor 412, a second resistor 413, a third resistor 414, and a reading coil 411. This unbalanced Wheatstone bridge unit 41 is designed specifically for accurately measuring the real part of the impedance of the reading coil 411. Different from the balanced Wheatstone bridge, the unbalanced Wheatstone bridge generates a voltage difference during measurement, which is usually used to detect tiny impedance changes. In the unbalanced state, the voltages of the two branches of the bridge are not equal, resulting in the voltmeter showing a non - zero voltage. This voltage difference can be used to calculate the standing - wave ratio across the read coil, and based on the standing - wave ratio, the real - part impedance value of the reading coil 411 can be calculated. Therefore, the unbalanced bridge can provide higher sensitivity. By simplifying the structure, the unbalanced Wheatstone bridge unit 41 reduces the connection points and the required space, making the circuit more compact. The reduction in the circuit volume also means a shorter signal transmission path, thereby improving the signal stability and response speed. Through optimized circuit design, while the volume of the unbalanced Wheatstone bridge is significantly reduced, it still maintains excellent measurement performance. This bridge can effectively achieve real - time detection of impedance changes, ensuring that the sensor still has high sensitivity and accuracy in complex environments.

[0026] To enhance the anti - interference ability of the detection device, preferably, the resistance values of the first resistor 412, the second resistor 413, and the third resistor 414 are equal. By using three resistors with the same resistance value, the resistance drift can be reduced at different temperatures, improving the stability and reliability of the bridge. This matching cancels out the errors caused by temperature changes, ensuring consistent measurement results. Using resistors with the same resistance value helps improve the circuit's resistance to interference signals, such as noise and interference signals, and improves measurement stability. Inconsistent resistance values will affect the repeatability of the measurement results. Three equal resistors ensure consistent measurement results for multiple measurements, improving the credibility of the data. As Figure 2 shown.

[0027] The unbalanced Wheatstone bridge unit 41 includes a first resistor 412, a second resistor 413, a third resistor 414, and a reading coil 411.. The functions of the unbalanced Wheatstone bridge unit 41:

[0028] (1) Measuring the standing - wave ratio to facilitate the subsequent host computer 1 to calculate the real - part impedance value of the reading coil 411: In the unbalanced state, the voltages of the two branches of the bridge are not equal, resulting in the voltmeter showing a non - zero voltage. This voltage difference can be used to calculate the standing - wave ratio across the read coil, and based on the standing - wave ratio, the real - part impedance value of the reading coil 411 can be calculated.

[0029] (2) Simplifying the circuit and reducing the volume of the overall circuit: The unbalanced Wheatstone bridge unit 41 reduces the connection points and the required space, making the circuit more compact.

[0030] (3) Improve anti-interference ability and reduce errors: By using three resistors with the same resistance value, the resistance drift can be reduced at different temperatures, and the resistance of the circuit to interference signals can be improved.

[0031] (4) Improve the reading accuracy and response speed of a detection device based on a standing wave ratio bridge: The unbalanced Wheatstone bridge generates a voltage difference during measurement, which can detect minute impedance changes. Moreover, the reduction in the circuit volume also means a shorter signal transmission path, improving the reading accuracy and response speed.

[0032] To enable the reading circuit to be unaffected by the coupling coefficient and accurately read the real part change of the impedance on both sides of the reading coil 411. The standing wave ratio bridge module 4 is the key to enabling the reading circuit to be unaffected by the coupling coefficient and accurately read the real part change of the impedance on both sides of the reading coil 411. In the standing wave ratio bridge module 41, the following four voltage amplitudes can be obtained through the unbalanced Wheatstone bridge unit 41 to calculate the standing wave ratio:

[0033] (1) Incident signal voltage (VI);

[0034] (2) Bridge unbalanced voltage (VR);

[0035] (3) Reading coil voltage (VZ);

[0036] (4) Known voltage on the load side (VS);

[0037] The specific calculation process is as follows:

[0038] First, the bridge unbalanced voltage VR can be expressed as:

[0039]

[0040] The reflection coefficient ρ at both ends of the reading inductor is:

[0041]

[0042] Thus, the standing wave ratio (SWR) at both ends of the reading inductor can be expressed as:

[0043]

[0044] In addition, the magnitude of the reading coil impedance (Z in ) can be expressed as:

[0045]

[0046] Furthermore, the real part value Re(Z in ) of the reading coil impedance can be calculated:

[0047]

[0048] Plot the real part of the calculated impedance on the host computer 1 to obtain the real part impedance curve. The frequency corresponding to the maximum value in the real part impedance curve is the resonance frequency of the measured sensor, achieving that the reading circuit is insensitive to the coupling coefficient and not restricted by the coupling distance.

[0049] To further improve the sensitivity and accuracy of signal detection, preferably, the diode model in the diode broadband detection unit 42 is the HSCH-9162 detection diode. By introducing the diode broadband detection unit 42 composed of HSCH-9162 detection diodes, the low-frequency components can be extracted from high-frequency signals, allowing for precise detection of weak signals in a complex signal environment. In addition, the diode broadband detection unit 42 shapes the received signal through rectification and filtering, making it suitable for subsequent processing, removing unnecessary high-frequency noise, and improving the signal quality. This process ensures that the data is clearer and conducive to subsequent analysis.

[0050] To improve the sensitivity of the overall device, preferably, the reading coil 411 is a planar weakly coupled spiral inductor made of copper. A planar weakly coupled spiral inductor is a weakly coupled spiral-shaped inductor wound on a plane. Compared with a planar spiral inductor, in a weakly coupled inductor, when the phase currents are equal, the mutual inductance fluxes from all coils cancel each other out, and only the leakage flux stores energy in the coupled inductor. This helps reduce energy loss and may improve the efficiency of reading the resonance frequency of the LC sensor. At the same time, its structure is more compact than that of traditional wire-wound inductors, easier to integrate, convenient to manufacture, suitable for applications with limited size and weight, and reduces the volume of the overall device. The material of the metal coil is copper because copper has a high conductivity, which improves the sensitivity of the overall detection circuit.

[0051] Preferably, the function of the reading coil 411 as a planar weakly coupled spiral inductor is as follows:

[0052] (1) Wireless measurement, coupled sensor: As an antenna, it is coupled with the LC sensor and, as a wireless signal test antenna, converts the change in the resonance frequency of the reading LC sensor into its own impedance change.

[0053] (2) Simplify the manufacturing process of the overall device: Both ends of the planar weakly coupled spiral inductor are the peripheries of the inductor, which is easy to integrate with the unbalanced Wheatstone bridge unit 41; one end of the planar spiral inductor is the periphery of the inductor, and the other end is in the inner circle of the inductor. If it is integrated with the unbalanced Wheatstone bridge unit 41, through holes need to be added, increasing the manufacturing difficulty.

[0054] To reduce the volume of a detection device based on a standing wave ratio bridge and improve its accuracy, preferably, the main control unit 22 includes an STM32 main control chip. This series of microcontrollers is renowned for its excellent performance and low power consumption characteristics. It can achieve rapid data processing while maintaining efficient energy utilization. In the STM32 microcontroller series, the built-in ADC module is responsible for converting analog signals into digital signals. This function helps simplify the circuit structure and reduce the overall volume of the device. At the same time, the flexibility and scalability of the STM32 chip facilitate the integration of additional sensors and communication modules into the circuit to meet diverse test requirements. The high-precision measurement function of this chip is crucial for ensuring the accuracy of standing wave ratio bridge detection, especially for the maintenance and fault diagnosis of radio frequency and wireless communication networks. Its broad frequency response range enables the circuit to handle test requirements in different frequency bands, and its compact design is convenient for carrying and on-site application. In addition, the STM32 chip is equipped with a user-friendly development environment and toolchain. The use of these tools helps simplify the test process, shorten the development cycle, and improve the test efficiency.

[0055] The STM32 chip has the following functions:

[0056] (1) Reduce the overall device power consumption: Control the DDS chip to generate a frequency sweep range suitable for the LC sensor, reducing the overall power consumption of the circuit.

[0057] (2) Reduce the overall device volume: Use its built-in AD conversion to sample the four voltages output by the detection module, simplifying and reducing the circuit.

[0058] (3) Improve the overall device efficiency: For convenient operation, to complete the detection function and subsequent data processing in a detection device based on a standing wave ratio bridge, communication with the host computer 1 needs to be completed.

[0059] To enhance the stability of the standing wave ratio bridge detection circuit, preferably, the signal generation unit 23 includes a signal generator model AD9850. The frequency range of the AD9850 covers from 0 Hz to 62.5 MHz. This broad frequency support ability can meet the requirements of the LC sensor change range. Its output tuning resolution is as high as 0.0291 Hz, ensuring the stability and reliability of the signal and providing a solid foundation for accurate test results. At the same time, the low phase noise characteristic of the AD9850 helps reduce unnecessary signal fluctuations and ensures the purity of the output signal. This is crucial because it significantly reduces errors in the measurement process and plays a key role in improving the measurement accuracy. The AD9850 has easy integration and programming flexibility, and can quickly adjust the frequency and phase. It not only improves the efficiency of the standing wave ratio bridge detection circuit but also greatly enhances the adaptability of the standing wave ratio bridge detection circuit in practical applications.

[0060] In order to improve the signal-to-noise ratio of the signal and enhance the reliability of reading data of the overall device. Preferably, the filtering unit 32 includes a low-pass filter, and the signal amplification unit 31 includes an operational amplifier.

[0061] During the use of the AD9850 in the signal processing module 3, due to its all-digital characteristics, a certain amount of clutter will be generated. These clutters mainly come from the non-ideal characteristics of digital devices, such as amplitude quantization error and phase truncation error, etc. These clutters follow the Nyquist sampling theorem and are distributed at the combination of the reference frequency and the output frequency. In order to reduce the influence of these clutters on the output signal, the filtering unit 32, i.e., a low-pass filter (LPF), is used to filter out the high-order harmonics. In practical applications, a 70 MHz low-pass filter is adopted to improve the signal-to-noise ratio of the waveform, thereby improving the quality of the output waveform. The AD9850 module adopts this low-pass filter to ensure that the output frequency is not interfered by the outside world and some clutters.

[0062] The AD9850 inside the signal processing module 3 contains a high-speed comparator, which can receive the converted output of the DAC (digital-to-analog converter) after external low-pass filtering and generate a low-jitter square wave output. In the use of the standing wave ratio bridge detection circuit, it is necessary to amplify the signal output by the AD9850 to meet the requirements of the subsequent standing wave ratio bridge module 4.

[0063] The filtering unit 32 is mainly used to reduce the clutter in the output signal of the AD9850 and improve the purity of the signal; while the signal amplification unit 31 is used to adjust the amplitude of the signal to meet specific application requirements. These two units work together to ensure that the AD9850 can generate a high-quality signal output. It can greatly suppress useless noise, improve the signal-to-noise ratio of the signal, and enhance the reliability of reading data of the overall device.

[0064] To ensure that the VSWR bridge detection device can achieve fast and high-quality communication with the host computer 1, thus meeting the requirements of more application scenarios, preferably, the communication unit 21 is a communication chip of ESP32. The ESP32 communication chip integrates 2.4GHz Wi-Fi and Bluetooth functions, and its excellent performance enables it to perform well in data transmission. Without the need for additional Ethernet or Wi-Fi modules, it greatly simplifies the hardware design. This highly integrated design not only saves space but also reduces power consumption, providing great convenience for users. The high-efficiency data transmission ability of the ESP32 communication chip ensures stable and reliable communication connections in various complex environments, whether it is industrial automation, smart home, or remote monitoring. Its built-in Wi-Fi and Bluetooth technologies enable the device to easily access the existing network architecture and support multiple communication protocols, ensuring seamless docking with the host computer 1. Through the ESP32 communication chip, the VSWR bridge detection circuit and the host computer 1 provide a fast and stable communication solution to meet their strict requirements for efficient data processing and transmission.

[0065] As Figure 3 shown is the detection process of a detection device based on a VSWR bridge. The input and output of its readout system are transmitted from the host computer 1 into the VSWR bridge detection circuit. The entire detection process is controlled by the control module 2. Its software first connects to the host computer 1 for initialization, and then the host computer 1 inputs the measured frequency range and frequency step. The communication unit 21 transmits them into the control module 2, which generates a control word according to the input value and gives it to the signal generation unit 23, that is, the DDS chip, to generate a frequency signal. At the same time, the built-in AD conversion of the main control unit 22 samples four voltage values, calculates the real part value of the impedance of the readout coil, and stores it. Subsequently, it enters the next measurement frequency point, repeats the above process until the full-frequency band measurement is completed. Finally, the data is transmitted back to the host computer 1 and an impedance real part curve is plotted. The frequency corresponding to the maximum value of the impedance real part curve is the resonance frequency of the sensor.

[0066] The above is a specific description of the preferred embodiment of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A detection device based on a standing wave ratio bridge, characterized in that: Including standing wave ratio bridge module, signal processing module, control module, host computer, power supply module; The standing wave ratio bridge module includes an unbalanced Wheatstone bridge unit and a diode broadband detection unit; The signal processing module includes a filtering unit and a signal amplifying unit; The control module includes a signal generating unit, a main control unit, and a communication unit; The standing wave ratio bridge module, the signal processing module, the control module and the host computer are respectively connected to the power supply module.

2. A detection device based on a standing wave ratio bridge according to claim 1, characterized in that: The unbalanced Wheatstone bridge unit includes a first resistor, a second resistor, a third resistor, and a reading coil.

3. A detection device based on a standing wave ratio bridge according to claim 2, characterized in that: The resistance values ​​of the first resistor, the second resistor and the third resistor are equal.

4. The detection device based on the standing wave ratio bridge according to claim 2, characterized in that: The reading coil is a planar weakly coupled spiral inductor, and the material is copper.

5. The detection device based on the standing wave ratio bridge according to claim 1, characterized in that: The diode broadband detection unit includes a detection diode of model HSCH-9162.

6. The detection device based on the standing wave ratio bridge according to claim 1, characterized in that: The main control unit includes an STM32 main control chip.

7. The detection device based on a standing wave ratio bridge according to claim 1, characterized in that: The signal generating unit comprises a signal generator of model AD9850.

8. The detection device based on a standing wave ratio bridge according to claim 1, characterized in that: The filtering unit includes a low-pass filter.

9. The detection device based on the standing wave ratio bridge according to claim 1, characterized in that: The signal amplifying unit includes an operational amplifier.

10. The detection device based on the standing wave ratio bridge according to claim 1, characterized in that: The communication unit includes a communication chip of model ESP32.

Images