LC resonant pressure sensor demodulation circuit
By combining a frequency sweep circuit, a transconductance amplifier circuit, a multiplication demodulation circuit, a DSP circuit, and a serial communication circuit, the design flaws and frequency calculation errors in the demodulation circuit of the LC resonant pressure sensor were solved, enabling efficient and accurate measurement by the wireless passive pressure sensor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HOHHOT POWER SUPPLY BUREAU OF INNER MONGOLIA POWER GRP CO LTD
- Filing Date
- 2025-03-03
- Publication Date
- 2026-04-14
AI Technical Summary
Existing LC resonant pressure sensor demodulation circuit designs suffer from problems such as discrepancies between experimental results and theoretical simulations, large circuit size and significant errors in resonant frequency calculation, and difficulty in achieving zero phase when reading the impedance phase angle of the coil under low coupling conditions.
The signal demodulation circuit, composed of a frequency sweep circuit, a transconductance amplifier circuit, a multiplication demodulation circuit, a DSP circuit, a power supply circuit, and a serial communication circuit, utilizes the principles of inductive coupling and multiplication demodulation to achieve wireless passive pressure measurement by measuring the real part of the impedance of the reading circuit.
It improves the efficiency and accuracy of data processing, reduces data processing errors and delays, simplifies circuit design, and ensures efficient and accurate signal transmission and measurement.
Smart Images
Figure CN224122079U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of modulation and demodulation, and in particular to a demodulation circuit for an LC resonant pressure sensor. Background Technology
[0002] Unlike traditional pressure sensors, wireless passive pressure sensors have broad application prospects in aerospace, medicine, and other fields due to their ability to operate in harsh environments. These sensors mostly utilize the principle of inductive coupling, achieving wireless detection of passive sensor signals through LC resonance, overcoming the shortcomings of wired detection under special conditions. Taking high-temperature pressure sensors as an example, the LC resonance scheme can overcome the technical bottleneck of electrical connections in leaded packaging, while simultaneously achieving physical isolation between the demodulation circuit and the high-temperature heat source, thus ensuring good sensor performance in harsh environments.
[0003] Currently, researchers focus on the fabrication of LC resonant pressure sensors, while research on demodulation circuits for such sensors is relatively limited. J. Coosemans et al. designed a demodulation circuit based on a voltage-controlled oscillator (VCO), with a frequency-selective network consisting of a readout coil and a voltage-controlled capacitor. When the voltage across the voltage-controlled capacitor changes, the VCO generates a signal of the corresponding frequency. Due to the mutual inductive coupling between the sensor and the readout coil, when the frequency of the output signal is near the sensor's resonant frequency, the amplitude of the output signal decreases compared to when there is no sensor in the readout coil. The sensor's resonant frequency is determined by measuring the frequency with the largest amplitude decrease. However, the experimental results of this design do not match the theoretical simulations, and the decrease in output signal amplitude is relatively small. Sérgio F. Picorim et al. proposed a real-time demodulation circuit that generates three fixed-frequency signals close to the sensor's resonant frequency. These signals are applied to an excitation coil to excite the LC sensor, while two receiving coils detect the intensity of these three fixed-frequency signals. The intensity of the signal with a frequency close to the sensor's resonant frequency decreases due to the coupling of the LC sensor, and the demodulation circuit uses this to determine the location of the resonant frequency. However, this circuit is quite large, and there is a certain calculation error in the resonant frequency. Furthermore, G. Jacquemod et al. designed an automatic closed-loop demodulation circuit, using a readout coil as the feedback network for the amplifier. The mutual inductive coupling between the readout coil and the sensor causes the impedance phase angle of the readout coil to cross zero near the resonant frequency, and the amplifier circuit will form positive feedback self-oscillation at the zero-crossing point of the phase angle. However, when the coupling coefficient between the readout coil and the sensor is low, it is difficult for the impedance phase angle of the readout coil to reach zero phase. Utility Model Content
[0004] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a signal demodulation circuit for an LC resonant pressure sensor. This circuit comprises a frequency sweep circuit, a transconductance amplifier circuit, a multiplication demodulation circuit, a DSP circuit, a power supply circuit, and a serial communication circuit. This circuit utilizes the principles of inductive coupling and multiplication demodulation to measure the real part of the reading circuit impedance, thereby achieving wireless and passive pressure measurement.
[0005] The frequency sweep circuit is connected to the DSP circuit and the transconductance amplifier circuit.
[0006] The multiplication demodulation circuit is connected to the frequency sweep circuit and the DSP circuit.
[0007] The DSP circuit is connected to the serial communication circuit, the frequency sweep circuit, and the multiplication demodulation circuit.
[0008] The serial communication circuit is connected to the DSP circuit.
[0009] The DSP chip used in the DSP circuit is a high-performance processor designed for efficient digital signal processing. DSP chips typically possess high-efficiency parallel processing capabilities, enabling them to process multiple data streams simultaneously, thus improving data processing efficiency. By properly configuring the DSP chip's processing parameters, the efficiency and accuracy of data processing can be ensured, avoiding errors and delays during the data processing process. Using a DSP chip for data processing can separate complex computational tasks from the main processor, thereby improving the overall system performance. The DSP chip can effectively manage data flow, preventing data loss or overflow during data processing. When the data generation rate temporarily exceeds the system's processing capacity, the DSP chip can temporarily store excess data to prevent data loss. When the system's processing capacity is faster than the data generation rate, the DSP chip provides buffering to ensure data is processed at an appropriate rate, avoiding data overflow. This chip features high-speed data processing capabilities and large-capacity memory support, with a simple and convenient interface, enabling it to efficiently process large amounts of data.
[0010] The frequency sweep circuit provides a variable frequency signal source for the subsequent demodulation circuit and measures the resonant frequency of the LC circuit.
[0011] Preferably, the AD9910 chip is used in the frequency sweep circuit. The AD9910 is a high-performance frequency synthesizer that, when equipped with a DSP chip, can precisely control frequency, phase, and amplitude. By accurately configuring the modulation parameters of the AD9910, the frequency output can be ensured to accurately meet the system requirements, thereby improving signal quality and accuracy. Using the AD9910 as the frequency synthesizer allows the frequency sweep task to be separated from the main processor, reducing its workload. The AD9910 provides smooth and continuous frequency adjustment, avoiding jumps or distortions during frequency synthesis. When rapid switching between different output frequencies is required, the AD9910 can respond quickly and achieve seamless switching. This chip has a sampling rate of up to 1 GSPS and is equipped with a 14-bit DAC, providing high-resolution and wide-spectrum frequency output. Therefore, selecting the AD9910 chip as the frequency sweep chip provides an accurate frequency-variable signal source for the demodulation circuit. When the signal source frequency approaches the resonant frequency of the LC circuit, the circuit output voltage will increase significantly, allowing the measurement of the LC circuit's resonant frequency.
[0012] Preferably, the OPA861 chip is used in the transconductance amplifier circuit. The OPA861 is a high-performance, wideband operational transconductance amplifier with precise timing and current control interfaces, effectively synchronizing and amplifying input signals. By precisely configuring the OPA861's control parameters, the timing and gain during signal amplification can be ensured to meet system requirements, thus avoiding signal distortion or errors. When the amplitude of the input signal varies significantly, the OPA861 can provide a stable amplification rate, ensuring the consistency of the output signal. Furthermore, the OPA861's fast response characteristics are particularly important for processing dynamic signals; it can quickly adapt to changes in the input signal, ensuring the real-time performance and accuracy of the output signal. Therefore, using the OPA861 chip as the transconductance amplifier circuit enables high-speed and high-precision conversion of the constant-amplitude voltage signal output from the frequency sweep circuit into a constant-amplitude current signal.
[0013] Preferably, the AD831 chip is selected as the mixer in the multiplication demodulation circuit. The AD831 is a high-performance, low-distortion, wide dynamic range active mixer, typically equipped with precise timing and level control interfaces, enabling efficient signal mixing. By correctly configuring the AD831's control signals, the signal quality and timing during the mixing process can be ensured to meet system requirements, thereby avoiding distortion or errors in signal processing. The AD831 provides a wide dynamic range and low-distortion mixing capability, suitable for processing signals of various power levels. Furthermore, the AD831's fast response characteristics can quickly adapt to changes in the input signal, ensuring the mixed signal is real-time and accurate. This chip offers multiple output modes and flexible configuration options, making it easy to integrate and apply in various electronic systems. Therefore, selecting the AD831 chip as the mixer in the multiplication demodulation circuit can quickly and accurately multiply the input and output signals of the readout circuit, improving system efficiency.
[0014] Preferably, the low-pass filter in the multiplication demodulation circuit is implemented using the MAX291 chip. The MAX291 is a high-performance 8th-order low-pass filter, typically equipped with a precise timing control interface, capable of effectively filtering signals. By correctly configuring the MAX291's control signals, the signal quality and timing during filtering can be ensured to meet system requirements, thereby avoiding distortion or errors in signal processing. The MAX291 provides high-precision low-pass filtering functionality, suitable for processing signals of various frequencies. It effectively filters out high-frequency noise, retaining useful signal components, thus ensuring the quality of the output signal. The MAX291's peripheral circuitry is simple, requiring no complex additional components, making the overall design more concise and efficient. Therefore, using the MAX291 chip in the mixer of the multiplication demodulation circuit allows for the rapid and accurate extraction of the real part of the impedance from the mixer's output signal, improving the system's efficiency.
[0015] Preferably, the serial communication circuit uses the MAX232 chip with an RS-232 interface. The MAX232 chip is robust and low-power, allowing for stable operation in various environments. The MAX232 is a highly integrated RS-232 communication controller chip that integrates level conversion and data buffering functions. Only this single chip is needed in the serial communication circuit, eliminating the need for multiple peripheral components, thus simplifying circuit design and layout and reducing system complexity. The MAX232 chip provides stable data communication, level conversion, and low power consumption, quickly and accurately converting the DSP circuit output to RS-232 levels for easy connection to a computer and display of the final measurement results.
[0016] Preferably, the power supply circuit uses the LM2678 chip as a high-efficiency buck regulator. The LM2678 chip features high efficiency and low power consumption, enabling stable operation under various load conditions while maintaining high energy efficiency. The LM2678 is a highly integrated buck regulator chip that integrates a switching regulator, internal MOSFETs, and multiple protection functions, including overcurrent protection and thermal shutdown. Using the LM2678 in the power management module reduces reliance on multiple external components, simplifying circuit design and layout and reducing system complexity. The LM2678 chip offers flexible configuration, allowing the output voltage to be adjusted according to system requirements, ensuring the stability and accuracy of the power output. Using the LM2678 as part of the power module effectively offloads the main processor, allowing it to focus more on other critical tasks, thereby improving overall system performance. Therefore, the power supply circuit based on the LM2678 chip provides an efficient and reliable power solution while maintaining design simplicity and ease of use. Attached image description:
[0017] Figure 1 This is a diagram of the signal demodulation circuit structure for an LC resonant pressure sensor.
[0018] Figure 2 This is a circuit diagram for a frequency sweep circuit;
[0019] Figure 3 This is a circuit diagram for a multiplication demodulation circuit.
[0020] Among them, 11 is the frequency sweep circuit, 12 is the transconductance amplifier circuit, 13 is the multiplication demodulation circuit, 14 is the DSP circuit, 15 is the power supply circuit, 16 is the serial communication circuit, 131 is the mixer, and 132 is the low-pass filter. Detailed implementation method:
[0021] To further explain the technical means adopted by this utility model to achieve its intended purpose, the following detailed description is provided in conjunction with the accompanying drawings and preferred embodiments:
[0022] A signal demodulation circuit for an LC resonant pressure sensor is disclosed. This circuit comprises a frequency sweep circuit 11, a transconductance amplifier circuit 12, a multiplication demodulation circuit 13, a DSP circuit 14, a power supply circuit 15, and a serial communication circuit 16. Utilizing the principles of inductive coupling and multiplication demodulation, the real part of the reading circuit impedance is measured, thereby achieving wireless passive pressure measurement.
[0023] Figure 1 The diagram shows the signal demodulation circuit structure of the LC resonant pressure sensor. The frequency sweep circuit 11 is connected to the DSP circuit 14 and the transconductance amplifier circuit 12.
[0024] The DSP circuit 14 uses a DSP chip, a high-performance processor designed for efficient digital signal processing. DSP chips typically have high-efficiency parallel processing capabilities, enabling them to process multiple data streams simultaneously, thus improving data processing efficiency. By properly configuring the processing parameters of the DSP chip, the efficiency and accuracy of data processing can be ensured, avoiding errors and delays during the data processing process. The DSP chip can effectively manage data flow, preventing data loss or overflow during data processing.
[0025] The transconductance amplifier circuit 12 uses the OPA861 chip. When the amplitude of the input signal changes significantly, the OPA861 can provide a stable amplification rate, ensuring the consistency of the output signal. The fast response characteristics of the OPA861 are particularly important for processing dynamic signals; it can quickly adapt to changes in the input signal, ensuring the real-time performance and accuracy of the output signal. Therefore, the OPA861 chip is selected as the transconductance amplifier circuit 12, which can convert the constant amplitude voltage signal output from the frequency sweep circuit 11 into a constant amplitude current signal at high speed and high precision.
[0026] Figure 2 This is a circuit diagram for a frequency sweep circuit. Frequency sweep circuit 11 provides a variable frequency signal source and measures the resonant frequency of the LC loop for subsequent demodulation circuits. Frequency sweep circuit 11 uses the AD9910 chip. The AD9910 is a high-performance frequency synthesizer that, when equipped with a DSP chip, can precisely control frequency, phase, and amplitude. By accurately configuring the modulation parameters of the AD9910, the frequency output can be ensured to accurately meet the system requirements, thereby improving signal quality and accuracy. Using the AD9910 as the frequency synthesizer allows the frequency sweep task to be separated from the main processor. This reduces the burden on the main processor, and the AD9910 provides smooth and continuous frequency adjustment, avoiding jumps or distortions during frequency synthesis.
[0027] The multiplication demodulation circuit 13 is connected to the frequency sweep circuit 11 and the DSP circuit 14.
[0028] Figure 3 This is the circuit diagram for the multiplication demodulation circuit. In the multiplication demodulation circuit 13, mixer 131 uses the AD831 chip. The AD831 is a high-performance, low-distortion, wide dynamic range active mixer, typically equipped with precise timing and level control interfaces, enabling efficient signal mixing. The AD831 provides a wide dynamic range and low-distortion mixing capability, suitable for processing signals of various power levels. The AD831's fast response characteristics are particularly important for processing dynamic signals; it can quickly adapt to changes in the input signal, ensuring the mixed signal is real-time and accurate. Therefore, using the AD831 chip for mixer 131 in the multiplication demodulation circuit 13 allows for fast and accurate multiplication of the input and output signals of the readout circuit, improving system efficiency.
[0029] The low-pass filter 132 in the multiplication demodulation circuit 13 uses the MAX291 chip. The MAX291 is a high-performance 8th-order low-pass filter, typically equipped with a precise timing control interface, capable of effectively filtering signals. The MAX291 provides high-precision low-pass filtering, suitable for processing signals of various frequencies. It effectively filters out high-frequency noise, retaining useful signal components, thus ensuring the quality of the output signal. Therefore, using the MAX291 chip for the low-pass filter 132 in the multiplication demodulation circuit 13 allows for fast and accurate extraction of the real part of the impedance from the signal output by the mixer 131, improving the system's efficiency.
[0030] The DSP circuit 14 is connected to the serial communication circuit 16, the frequency sweep circuit 11, and the multiplication demodulation circuit 13.
[0031] The serial communication circuit 16 uses the MAX232 chip with an RS-232 interface. The MAX232 chip is characterized by its robustness and low power consumption. It is a highly integrated RS-232 communication controller chip that integrates level conversion and data buffering functions. The MAX232 chip provides stable data communication, level conversion, and low power consumption, and can quickly and accurately convert the output of the DSP circuit 14 to RS-232 level, facilitating connection to a computer and displaying the final measurement results on the computer.
[0032] The power supply circuit 15 uses the LM2678 chip as a high-efficiency step-down regulator design. Based on the LM2678 chip, the power supply circuit 15 provides an efficient and reliable power solution while maintaining design simplicity and ease of use.
Claims
1. A demodulation circuit for an LC resonant pressure sensor, characterized in that, The demodulation circuit consists of a frequency sweep circuit, a transconductance amplifier circuit, a multiplication demodulation circuit, a DSP circuit, a power supply circuit, and a serial communication circuit. The frequency sweep circuit is connected to the DSP circuit and the transconductance amplifier circuit; The multiplication demodulation circuit is connected to the frequency sweep circuit and the DSP circuit; The DSP circuit is connected to the serial communication circuit, the frequency sweep circuit, and the multiplication demodulation circuit. The serial communication circuit is connected to the DSP circuit.
2. The LC resonant pressure sensor demodulation circuit as described in claim 1, characterized in that, The frequency sweep circuit uses the AD9910 chip to provide a variable frequency signal source for the subsequent demodulation circuit and to measure the resonant frequency of the LC circuit.
3. The LC resonant pressure sensor demodulation circuit as described in claim 1, characterized in that, The transconductance amplifier circuit uses the OPA861 chip to convert the constant amplitude voltage signal output by the frequency sweep circuit into a constant amplitude current signal.
4. The LC resonant pressure sensor demodulation circuit as described in claim 1, characterized in that, The multiplication demodulation circuit uses an AD831 mixer to perform the mixing function, multiplying the input and output signals of the frequency sweep circuit.
5. The LC resonant pressure sensor demodulation circuit as described in claim 1, characterized in that, The multiplication demodulation circuit uses MAX291 to implement low-pass filtering and extract the real part of the impedance information.
6. The LC resonant pressure sensor demodulation circuit as described in claim 1, characterized in that, The serial communication circuit uses the MAX232 chip to convert the output of the DSP circuit to RS-232 level.
7. The LC resonant pressure sensor demodulation circuit as described in claim 1, characterized in that, The power supply circuit uses the LM2678 chip, which is responsible for providing power to the chips in each module.