Cosine curve fitting based method for stabilizing working point of electric field sensor

Abstract

The application discloses a cosine curve fitting-based electric field sensor working point stabilizing method, and is based on an electric field sensing system for electric field measurement, and comprises the following steps: controlling the wavelength tuning range of a tunable linearly polarized laser to be greater than 40 nm, and scanning N discrete wavelength points, wherein N>10; collecting the feedback voltage corresponding to each wavelength point to form a wavelength-voltage data set, wherein the wavelength points in the wavelength-voltage data set are measured wavelength points, and the feedback voltage therein is measured feedback voltage; adopting a least square method to fit the wavelength-voltage data set to a cosine function; extracting the wavelength of each measured wavelength point and a theoretical linear working point, calculating an absolute deviation, and selecting the measured wavelength point with the minimum absolute deviation as a linear working wavelength; and setting the output wavelength of the tunable linearly polarized laser as the linear working wavelength. According to the technical scheme, the accuracy and effectiveness of working point identification can be improved, and the stability of electric field measurement under normal operation can be ensured.

Description

Technical Field

[0001] This invention relates to the field of electric field sensor technology, and more specifically, to a method for stabilizing the operating point of an electric field sensor based on cosine curve fitting. Background Technology

[0002] Electric field sensors, as important measuring instruments, are widely used in fields such as power, communications, and medicine to monitor and analyze the intensity and distribution of electric fields in real time. With the development of technology, the requirements for the accuracy and reliability of electric field sensors in measuring electric field intensity under complex environments are becoming increasingly stringent.

[0003] Existing electric field sensors often experience operational instability due to environmental changes (such as temperature and humidity variations) and equipment aging, resulting in nonlinearity in the sensor output signal and inaccurate measurement results. This instability not only affects the accuracy of measurement results but can also lead to a decline in the overall system performance. Current methods to address this issue involve simple processing of the feedback signal, such as finding the maximum and minimum values ​​of the feedback voltage and determining the operating wavelength by taking the intermediate value. While this method can improve operational stability to some extent, it has significant limitations in practical application. Specifically, when there is a large deviation between the feedback signal curve and the theoretical model (such as a cosine curve), the intermediate value method struggles to accurately identify the optimal operating point, leading to inconsistencies and poor reproducibility in the measurement results. Some technologies employ iterative scanning methods, which determine the target operating frequency by gradually narrowing the scanning range by detecting the difference in electrical feedback signals between adjacent scanning frequency ranges. However, these methods rely on comparisons of local signal differences, and are prone to misjudgment when there is noise interference in the feedback signal. The iterative process takes a long time (usually >3 seconds), making it difficult to meet the requirements of scenarios with high real-time requirements. Furthermore, they do not consider the deviation between the actual response curve of the sensor and the ideal cosine model, resulting in a significant decrease in accuracy under non-ideal operating conditions.

[0004] On the other hand, current application environments also require inductive sensors to have higher sensitivity and better anti-interference capabilities, while the method of stabilizing the operating point through intermediate values ​​does not meet the accuracy requirements of practical applications. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a method for stabilizing the operating point of an electric field sensor based on cosine curve fitting. This method involves measuring the electric field using an electric field sensing system to determine the wavelength of the stabilization point. The electric field sensing system includes a tunable linearly polarized laser, an operating point stabilization module, an electric field probe, and a PD+ low-noise amplifier. The tunable linearly polarized laser is used to output an optical signal. Determining the stable point wavelength includes the following steps: The wavelength tuning range of the tunable linear polarizer is controlled to be greater than 40 nm, and N discrete wavelength points are scanned, where N>10; The feedback voltage corresponding to each wavelength point is collected to form a wavelength-voltage dataset. The wavelength points in the wavelength-voltage dataset are the measured wavelength points, and the feedback voltages in the dataset are the measured feedback voltages. The wavelength-voltage dataset is fitted to the cosine function V(λ)=A·cos(B·λ+C)+D using the least squares method, where λ is the wavelength and A, B, C, and D are constants. Calculate the derivative of the cosine function, and extract the point with the largest absolute value of the derivative within the scanning range as the theoretical linear operating point. The derivative is expressed as dV / dλ = -A·B·sin(B·λ+C). Calculate the wavelength λ_linear at the theoretical linear operating point; Calculate the wavelength λ for each measured wavelength point in the wavelength-voltage dataset, calculate the absolute deviation between the measured feedback voltage at the measured wavelength point and the fitted voltage value corresponding to the theoretical linear operating point wavelength, and select the measured wavelength point with the smallest absolute deviation as the linear operating wavelength λ_real. The output wavelength of the tunable linearly polarized laser is set to the linear operating wavelength λ_real.

[0006] Among them, the least squares method uses the Levenberg-Marquardt algorithm to adjust parameters A, B, C and D so that the mean square error of the fitted curve and the measured data reaches the minimum value.

[0007] The voltage deviation is the absolute error |V_real(λ) - V_calc(λ_linear)|, where V_real(λ) is the feedback voltage value measured at the actual wavelength point λ, and V_calc(λ_linear) is the theoretical linear operating point voltage value calculated by fitting a cosine function.

[0008] Furthermore, the electric field probe is used to return signals that reflect the interference and influence of the electric field environment; the operating point stabilization module is used to control the stabilization adjustment of the operating point; the operating point stabilization adjustment includes calculating the linear operating wavelength, determining whether the operating point is stable, if not, re-executing the steps to determine the stable wavelength; if the operating point is stable, outputting the linear operating wavelength. The stable operating point refers to the absolute deviation between the measured feedback voltage at the measured wavelength point and the fitted voltage value corresponding to the theoretical linear operating point wavelength being less than a specified value.

[0009] Furthermore, the tuning time of the tunable linear polarization laser is less than 0.2 s, the input optical power is 16 dBm, the wavelength scanning range is 1520-1560 nm, and the step size is 4 nm. The operating point stabilization module includes a photoelectric conversion circuit, a filter amplification circuit, a TTL / RS232 level protocol conversion circuit, and an optical fiber link, which are used to realize self-test and control functions. The control function is used to achieve stable adjustment of the operating point.

[0010] The self-test function is used to monitor the working status of components such as the tunable linearly polarized laser and fiber optic link in the electric field sensing system in real time, ensuring the normal operation of the electric field sensing system.

[0011] The electric field sensing system also includes indicator lights, control buttons, and signal output components; Indicator lights are used to indicate the self-test status and the calculation status of the linear operating wavelength; The control buttons are used to manually start and stop the operation of the electric field sensor; The signal output component includes a radio frequency output line for outputting a linear operating wavelength.

[0012] When running the electric field sensing system, the first step is to initialize the electric field sensing system, which includes: initializing the operating point stabilization module and performing a self-test of the electric field sensing system. The initialization of the operating point stabilization module includes initializing the components of the operating point stabilization module and waiting 10 seconds to ensure that the temperature control function of the tunable linear polarizer is operating normally. The system self-test includes checking each component of the electric field sensing system to determine whether it is working properly; if it is working properly, electric field measurement can be performed; if an abnormality is found during the self-test, the abnormality will be indicated by the indicator light and the self-test will stop.

[0013] This invention proposes an electric field sensing system capable of wavelength adjustment based on feedback voltage. The system performs wavelength scanning of the feedback voltage and combines this with cosine curve fitting techniques to more accurately determine the optimal linear operating wavelength. During operation, the system samples actual interference and influences from the application environment, and adjusts the wavelength based on the sampling results, significantly improving the accuracy and effectiveness of operating point identification. Furthermore, a self-testing module is introduced to monitor the status of each component in real time, ensuring the stability of electric field measurements under normal operating conditions. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of an electric field sensing system provided according to an embodiment of the present invention; Figure 2 This is a step diagram of the method for stabilizing the operating point of an electric field sensor according to an embodiment of the present invention; Figure 3This is a schematic diagram comparing the operating point curve and the cosine fitting curve provided in an embodiment of the present invention. Detailed Implementation

[0015] The specific implementation of the present invention will now be described in detail with reference to the accompanying drawings.

[0016] The electric field sensor operating point stabilization method proposed in this invention is based on, for example, Figure 1 The electric field sensing system shown is implemented by first running the electric field sensing system and then measuring the electric field based on the electric field sensing system.

[0017] During the electric field measurement process, feedback voltage is collected, and a cosine curve is fitted using the feedback voltage. The wavelength corresponding to the linear point is calculated using the fitted cosine curve, and the wavelength corresponding to the linear point is output by the tunable linearly polarized laser to determine the stable point wavelength.

[0018] like Figure 1 As shown, the electric field sensing system comprises a tunable linearly polarized laser, an operating point stabilization module, an electric field probe, and a PD+ low-noise amplifier. These components are integrated into the operating point control board, resulting in high integration, a small footprint, and adaptability to various application environments. The circuit design includes two-channel photoelectric sampling (outputting and returning optical path monitoring information), two-channel serial communication, multiple button and indicator light pin outputs, and a reserved display screen interface for future improvements.

[0019] 1) A tunable linearly polarized laser is used to execute commands and output optical signals. Its wavelength tuning range is greater than 40 nm, the tuning time is less than 0.2 s, and the input optical power is 16 dBm. The output optical signal can constitute output optical path monitoring information. 2) Electric field probe: used to respond to the optical signal output by the tunable linearly polarized laser, and combined with the return signal from the polarization-maintaining optical splitter and polarization-maintaining circulator to form the return optical path monitoring information; due to factors such as interference in the application environment and equipment aging, there is a certain difference between the return optical path monitoring information and the output optical path monitoring information, and the difference can reflect the interference and influence of the electric field environment. The electric field probe has a frequency range from 100 kHz to 18 GHz and a peak field strength measurement range from 0.2 kV / m to 30 kV / m. PD+ Low Noise Amplifier: Features a 3 dB bandwidth of 18 GHz to meet system bandwidth requirements.

[0020] 3) The operating point stabilization module is used to achieve operating point stabilization adjustment; the operating point stabilization adjustment refers to determining whether the operating point stabilization state has been reached. If not, a wavelength modulation command is sent to the tunable linear polarizer to restart the determination of the path length of the stabilization point wavelength; if the operating point stabilization state has been reached, the linear operating wavelength is output.

[0021] Structurally, the operating point stabilization module includes a photoelectric conversion circuit, a filter amplification circuit, a TTL / RS232 level protocol conversion circuit, and an optical fiber link, which are used to realize self-test and control functions. The self-test function is used to monitor the working status of components such as the tunable linear polarizer and fiber optic link in the electric field sensing system in real time to ensure the normal operation of the electric field sensing system; the control function is used to achieve stable adjustment of the operating point.

[0022] exist Figure 1 It can also be seen that the input of the operating point stabilization module includes two photoelectric samplings, namely the output optical path monitoring information and the return optical path monitoring information; When implementing the control function, the preset wavelength is determined based on the comparison value between the output optical path monitoring information and the return optical path monitoring information.

[0023] 4) In addition to the above, the electric field sensing system also includes indicator lights, control buttons, and signal output components. Indicator lights indicate the self-test status and the calculation status of the linear operating wavelength. For example, if the control board is detected to be malfunctioning during the self-test, the corresponding red light will illuminate; if the tunable linear polarizer is in an abnormal state, the corresponding red light will illuminate; after the linear operating wavelength is output, the green light will illuminate. Control buttons are used to manually start and stop the electric field sensor. The signal output components include radio frequency output lines for outputting the linear operating wavelength.

[0024] The core idea of ​​the electric field sensor operating point stabilization method proposed in this invention is to continuously adjust the output wavelength of the electric field sensor through a tunable linear polarizer during the operation of the electric field sensor, and to collect feedback voltage data after each wavelength adjustment. By repeatedly collecting feedback voltage data, a complete operating point curve is formed, and the optimal operating point wavelength is selected from it.

[0025] The specific implementation process is as follows: Figure 2 As shown, it includes the following steps: Step S200: When running the electric field sensing system, the electric field sensing system initialization is performed first, including: Step S201 initialization of the operating point stabilization module and S202 electric field sensing system self-test; Step S201 Initializes the operating point stabilization module, which includes initializing the components of the operating point stabilization module and waiting 10 seconds to ensure that the temperature control function of the tunable linear polarizer is operating normally. After the temperature control function of the tunable linear polarizer is operating normally, step S202 is executed, sending an enable command to the tunable linear polarizer. The tunable linear polarizer responds to the enable command and outputs an optical signal at a preset wavelength.

[0026] Step S202, the self-test of the electric field sensing system, includes testing each component of the electric field sensing system to determine whether it is working properly; if it is working properly, electric field measurement can be performed; if an abnormality is found during the self-test, the abnormality is indicated by the indicator light and the self-test is stopped.

[0027] During self-testing, the system sequentially checks whether the control board (main controller), tunable linear polarizer, fiber optic link, and low-noise amplifier are functioning properly. If an abnormality is detected, the corresponding red light illuminates to prompt the operator to check; if no abnormality is detected, the green light illuminates to indicate that the system can perform electric field measurements.

[0028] This step may also include judging manual commands, that is, after the system self-test is completed and there are no abnormalities, checking whether the calibration key has been pressed. If it is not pressed, return to the self-test process; if it is pressed, proceed to step S210 electric field measurement; S210 electric field measurement includes the following steps: Step S211: Control the wavelength tuning range of the tunable linear polarizer to be greater than 40nm, scan N discrete wavelength points, where N>10, the wavelength scanning range is 1520-1560nm, and the step size is 4nm; Simultaneously, the feedback voltage corresponding to each wavelength point is collected to form a wavelength-voltage dataset.

[0029] The wavelength points in the wavelength-voltage dataset are the measured wavelength points, and the feedback voltages are the measured feedback voltages.

[0030] This invention provides an embodiment for implementing wavelength scanning, and the implementation code is as follows: # Wavelength scanning parameter settings start_wavelength = 1520 end_wavelength = 1560 step = 4 wavelength_points = [start_wavelength + i*step for i in range(11)] # 11 points Step S212: Perform cosine curve fitting; specifically including the following: In this step, the least squares method is used to fit the measured wavelength points in the wavelength-voltage dataset to the cosine function V(λ)=A·cos(B·λ+C)+D, where λ is the wavelength and A, B, C, and D are constants; During the fitting process, the Levenberg-Marquardt algorithm was used to adjust parameters A, B, C, and D to minimize the mean square error between the fitted curve and the measured data.

[0031] Calculate the derivative of the cosine function, and extract the point with the largest absolute value of the derivative within the scanning range as the theoretical linear operating point, where the derivative is expressed as dV / dλ = -A·B·sin(B·λ+C).

[0032] This invention provides Embodiment 2, which implements cosine curve fitting. The implementation method is as follows: import numpy as np from scipy.optimize import curve_fit # Define the cosine function model defcos_func(λ, A, B, C, D): return A * np.cos(B * λ + C) + D # Perform least squares fitting popt, pcov = curve_fit( cos_func, wavelengths voltages, p0=[0.5*(max_v-min_v),2*np.pi / 40,0,(max_v+min_v) / 2], #Initial parameters method='lm' # Levenberg-Marquardt algorithm ) Calculate the wavelength λ_linear of the theoretical linear operating point; Calculate the wavelength λ for each measured wavelength point in the wavelength-voltage dataset, calculate the absolute deviation between the measured feedback voltage at the measured wavelength point and the fitted voltage value corresponding to the theoretical linear operating point wavelength, and select the measured wavelength point with the smallest absolute deviation as the linear operating wavelength λ_real; in this step, the voltage deviation is the absolute error |V_real(λ) - V_calc(λ_linear)|. Wherein, V_real(λ) is the feedback voltage value measured at the actual wavelength point λ, where λ represents the discrete wavelength point of the actual output of the tunable laser (such as 1520nm, 1524nm, etc.), and it is emphasized that this is the physical quantity value actually measured by the photoelectric conversion circuit. For example, when λ=1540nm, V_real(1540) represents the measured voltage value corresponding to that wavelength point.

[0033] V_calc(λ_linear) is the theoretical linear operating point voltage value calculated by fitting a cosine function, where λ_linear is the theoretical wavelength corresponding to the point of maximum derivative (obtained analytically). It is emphasized that this is a calculated value based on a mathematical model. For example, if λ_linear = 1542.3 nm, then V_calc(1542.3) = A·cos(B×1542.3 + C) +D.

[0034] The present invention also provides Embodiment 3, which implements the method for determining the operating point as follows: #Calculate the extreme points of the derivative λ_dense = np.linspace(1520,1560,1000) #Dense Sampling dVdλ =-popt[0]*popt[1]*np.sin(popt[1]*λ_dense + popt[2]) #Analytic derivative λ_linear = λ_dense[np.argmax(np.abs(dVdλ))] #Theoretical Linear Point #Voltage Deviation Compensation voltage_diff =[abs(v - cos_func(λ_linear,*popt))for λ,v inzip(wavelengths, voltages)] λ_real = wavelengths[np.argmin(voltage_diff)] #Final Output Wavelength Step S213: Determine whether the operating point has been reached; if not, repeat step S211 and start collecting feedback voltage again; if the operating point has been reached, proceed to step S214. The stable operating point state is achieved through the operating point stabilization module. In this step, the stable operating point state means that the absolute deviation between the measured feedback voltage at the measured wavelength point and the fitted voltage value corresponding to the theoretical linear operating point wavelength is less than a specified value, for example: absolute deviation <0.05V.

[0035] Step S214: Set the output wavelength of the tunable linearly polarized laser to the linear operating wavelength λ_real; Step S220: At this point, the stable operating point is indicated by indicator lights or other means. That is, the final output wavelength of the tunable linearly polarized laser is the linear operating wavelength calculated in step S215.

[0036] To verify the effectiveness of the method of the present invention, an experiment for measuring nanosecond-level strong electric field pulses is provided. The experimental system includes a nanosecond-level high-voltage pulse source, a TEM cell, a high-power attenuator, an electric field sensing system host, and a high-speed oscilloscope. During the test, the high-voltage pulse source outputs a high-voltage pulse to the TEM cell through an RF line, generating a nanosecond-level high-voltage pulse signal at the sensor. The signal is then output to the high-speed oscilloscope for recording and analysis via the high-power attenuator.

[0037] Experimental results are as follows Figure 3 As shown, experimental results indicate that the operating wavelength obtained by the method of this invention differs from the curve fitting result by only 0.1 nm, verifying the reliability and accuracy of the cosine curve fitting-based operating point stabilization method in practical applications. Furthermore, by comparing the original waveform with the waveform measured by the sensor, it can be seen that they are essentially consistent in shape and temporal characteristics, further demonstrating the effectiveness of the method of this invention in high-precision measurement.

[0038] The cosine curve fitting-based method for stabilizing the operating point of an electric field sensor provided by this invention can significantly improve the stability of the sensor's operating point under various environmental conditions, reducing the measurement error to within 0.1 nm, which is a clear advantage over traditional methods. Furthermore, this method is simple in structure, low in cost, easy to implement, and suitable for electric field measurement needs in various complex environments.

[0039] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the present invention is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for stabilizing the operating point of an electric field sensor based on cosine curve fitting, characterized in that, Electric field measurement based on electric field sensing system to determine the steady-state wavelength; The electric field sensing system includes a tunable linearly polarized laser, an operating point stabilization module, an electric field probe, and a PD+ low-noise amplifier. The tunable linearly polarized laser is used to output optical signals. Determining the stable point wavelength includes the following steps: The wavelength tuning range of the tunable linear polarizer is controlled to be greater than 40 nm, and N discrete wavelength points are scanned, where N>10; The feedback voltage corresponding to each wavelength point is collected to form a wavelength-voltage dataset. The wavelength points in the wavelength-voltage dataset are the measured wavelength points, and the feedback voltages in the dataset are the measured feedback voltages. The wavelength-voltage dataset is fitted to a cosine function V(λ) = A·cos(B·λ+C)+D using the least squares method, where λ is the wavelength and A, B, C, and D are constants. Calculate the derivative of the cosine function, and extract the point with the largest absolute value of the derivative within the scanning range as the theoretical linear operating point, where the derivative is expressed as dV / dλ = -A·B·sin(B·λ+C); Calculate the wavelength λ_linear of the theoretical linear operating point; Calculate the wavelength λ for each measured wavelength point in the wavelength-voltage dataset, calculate the voltage deviation between the measured feedback voltage at the measured wavelength point and the fitted voltage value corresponding to the theoretical linear operating point wavelength, and select the measured wavelength point with the smallest voltage deviation as the linear operating wavelength λ_real; where the voltage deviation is the absolute error |V_real(λ) - V_calc(λ_linear)|, where V_real(λ) is the feedback voltage value measured at the actual wavelength point λ, and V_calc(λ_linear) is the theoretical linear operating point voltage value calculated by fitting a cosine function; The output wavelength of the tunable linearly polarized laser is set to the linear operating wavelength λ_real.

2. The method for stabilizing the operating point of an electric field sensor according to claim 1, characterized in that, The least squares method uses the Levenberg-Marquardt algorithm to adjust parameters A, B, C, and D to minimize the mean square error between the fitted curve and the measured data.

3. The method for stabilizing the operating point of an electric field sensor according to claim 1, characterized in that, The electric field probe is used to return signals that reflect the interference and influence of the electric field environment; the operating point stabilization module is used to control the operating point stabilization adjustment; the operating point stabilization adjustment includes calculating the linear operating wavelength, determining whether the operating point stabilization state has been reached, and if not, re-executing the step of determining the stabilization point wavelength; if the operating point stabilization state has been reached, outputting the linear operating wavelength. The stable operating point refers to the absolute deviation between the measured feedback voltage at the measured wavelength point and the fitted voltage value corresponding to the theoretical linear operating point wavelength.

4. The method for stabilizing the operating point of an electric field sensor according to claim 1, characterized in that, The tunable linearly polarized laser has a tuning time of less than 0.2 s, an input optical power of 16 dBm, a wavelength scanning range of 1520-1560 nm, and a step size of 4 nm. The operating point stabilization module includes a photoelectric conversion circuit, a filter amplification circuit, a TTL / RS232 level protocol conversion circuit, and an optical fiber link, which are used to realize self-test and control functions. The control function is used to achieve stable adjustment of the operating point.

5. The method for stabilizing the operating point of an electric field sensor according to claim 4, characterized in that, The self-test function is used to monitor the operating status of the tunable linearly polarized laser, the operating point stabilization module, the electric field probe, and the PD+ low-noise amplifier in the electric field sensing system in real time, so as to ensure the normal operation of the electric field sensing system.

6. The method for stabilizing the operating point of an electric field sensor according to claim 5, characterized in that, The electric field sensing system also includes indicator lights, control buttons, and signal output components; The indicator light is used to indicate the self-test status and the calculation status of the linear working wavelength; The control buttons are used to manually start and stop the operation of the electric field sensor; The signal output component includes a radio frequency output line for outputting a linear operating wavelength.

7. The method for stabilizing the operating point of an electric field sensor according to claim 6, characterized in that, When the electric field sensing system is running, the electric field sensing system initialization is first performed, including: initializing the operating point stabilization module and the electric field sensing system self-test; The initialization of the operating point stabilization module includes initializing the components of the operating point stabilization module and waiting 10 seconds to ensure that the temperature control function of the tunable linear polarizer is operating normally. The system self-test includes testing each component of the electric field sensing system to determine whether it is working properly; if it is working properly, electric field measurement can be performed; if an abnormality is found during the self-test, the abnormality is indicated by an indicator light and the self-test is stopped.

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