A signal transmission system and method for high voltage circuit testing

Abstract

A signal transmission system and method for high-voltage circuit test, comprising a signal input module, a signal transmission module, a signal output module, a bias adjustment module and a DC measurement module. The signal input module is used for accessing the original transmission signal. The bias adjustment module is used for generating a DC bias compensation signal according to the compensation parameter output by the DC measurement module. The original transmission signal is compensated by using the DC bias compensation signal, and the compensated original transmission signal is output as a to-be-transmitted signal to the signal transmission module. The signal transmission module is used for transmitting the to-be-transmitted signal by using an optical fiber. The DC measurement module is used for obtaining the compensation parameter by detecting the DC bias loss in the transmission process of the signal transmission module. The signal output module is used for outputting the original transmission signal. Since the gain compensation of the original transmission signal is performed at the front end of the signal transmission, the input and output of the signal transmission system are consistent, the calibration mechanism is simplified, and the accuracy and efficiency of the signal transmission are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of high-voltage circuit testing technology, and specifically to a signal transmission system and method for high-voltage circuit testing. Background Technology

[0002] In high-voltage power electronics testing scenarios, traditional electrical measurement techniques suffer from drawbacks such as susceptibility to ground loop interference, difficulty in ensuring measurement accuracy under high common-mode voltage environments, and the easy submersion of effective signals by electromagnetic noise in environments with strong EMI electromagnetic interference. To overcome these shortcomings, fiber optic isolation technology is required for the transmission of signals acquired during testing and measurement. This technology uses optical fiber as the transmission carrier and optical signals as the transmission medium, leveraging the inherent characteristics of optical fiber such as insulation isolation, resistance to electromagnetic interference, low transmission loss, and wide bandwidth to achieve complete electrical isolation between the high-voltage circuit under test and the downstream testing system, while simultaneously enabling long-distance, distortion-free signal transmission.

[0003] Fiber optic isolated transmission is an optical signal transmission system based on an "electro-optical-electrical" architecture. It includes electro-optic modulation (modulating electrical signals into optical signals using lasers and photodiodes), a transmission channel (optical signals are transmitted over long distances in isolation via optical fibers), and photoelectric demodulation (the optical signals are restored to electrical signals by photodetectors / PD tubes before output). Fiber optic isolated transmission technology has become a core technology for testing new energy power semiconductors, high-voltage precision measurements, special power supply testing, and various scenarios requiring electrical safety isolation. However, when applied to high-voltage power electronics testing scenarios, fiber optic isolated transmission technology still faces technical challenges such as complex separation calibration during high- and low-frequency signal separation "electro-optical-electrical" conversion, signal distortion due to the inherent DC bias of optoelectronic devices, and difficulties in real-time calibration of end-to-end gain variations. Summary of the Invention

[0004] This application aims to address the technical shortcomings of existing fiber optic isolated transmission technology when applied to high-voltage testing scenarios in power electronics.

[0005] According to the first aspect, one embodiment provides a signal transmission system for high-voltage circuit testing, including a signal input module, a signal transmission module, a signal output module, a bias adjustment module, and a DC measurement module;

[0006] The signal input module is used to receive the original transmission signal;

[0007] The bias adjustment module is connected to the signal input module and the DC measurement module respectively, and is used to receive the compensation parameters output by the DC measurement module and generate a DC bias compensation signal based on the compensation parameters.

[0008] The signal input module is also used to compensate the original transmission signal with the DC bias compensation signal, and output the compensated original transmission signal as the signal to be transmitted to the signal transmission module.

[0009] The signal transmission module is used to first modulate the signal to be transmitted from an electrical signal into an optical signal, and then demodulate the optical signal transmitted through the optical fiber back into an electrical signal.

[0010] The DC measurement module is used to detect the DC bias loss of the signal to be transmitted during the transmission process of the signal transmission module, obtain the compensation parameters corresponding to the DC bias loss, and send the compensation parameters to the bias adjustment module so that the bias adjustment module generates a DC bias compensation signal according to the compensation parameters, so that the signal output by the signal transmission module is consistent with the DC bias voltage of the original transmission signal connected to the signal input module.

[0011] The signal output module is used to output the original transmitted signal of the demodulated return signal.

[0012] In one embodiment, the original transmission signal is a calibration signal during the calibration phase and a test signal acquired by an external testing device during the testing phase.

[0013] The DC measurement module is connected to the input and output terminals of the signal transmission module, respectively, and is used to detect the first voltage signal at the input terminal of the signal transmission module and the second voltage signal at the output terminal of the signal transmission module.

[0014] During the calibration phase, the signal input module inputs a calibration signal. The DC measurement module obtains initial compensation parameters based on the first difference between the detected first and second voltage signals, and sends these initial compensation parameters to the bias adjustment module for initial configuration. The bias adjustment module generates a first bias voltage based on the initial compensation parameters and uses this first bias voltage to compensate the calibration signal. The compensated calibration signal is then output to the signal transmission module. The DC measurement module detects the second voltage signal after the compensated calibration signal has been transmitted through the signal transmission module, calculates the second difference between the compensated second voltage signal and the calibration signal to obtain fine-tuning compensation parameters, and sends these fine-tuning compensation parameters to the bias adjustment module. The bias adjustment module superimposes the fine-tuning compensation parameters and the initial compensation parameters to generate a second bias voltage, and uses this second bias voltage to compensate the original transmitted signal. The DC measurement module cyclically calculates the second difference until the second difference is less than a preset threshold, where the preset threshold includes 0.

[0015] During the testing phase, the signal input module inputs the test signal from the external test equipment, and the bias adjustment module uses a second bias voltage corresponding to the second difference within the preset threshold to compensate the test signal, and outputs the compensated test signal as the signal to be transmitted to the signal transmission module.

[0016] In one embodiment, the signal input module includes:

[0017] The signal access unit is used to access the signal under test collected by external testing equipment;

[0018] A standard signal generation unit is used to generate calibration signals with preset electrical parameters;

[0019] The signal input selection unit is connected to both the signal access unit and the standard signal generation unit. It is used to turn on the standard signal generation unit during the calibration phase and use the calibration signal as the original transmission signal; and to turn on the signal access unit during the testing phase and use the signal under test as the original transmission signal.

[0020] In one embodiment, the bias adjustment module includes a bias adjustment device and a bias amplifier circuit;

[0021] The bias adjustment device is connected to the DC measurement module and is used to generate a bias voltage based on the compensation parameters output by the DC measurement module.

[0022] The signal input selection unit includes a transmission signal amplification circuit;

[0023] The transmission signal amplification circuit is connected to the output terminal of the bias amplification circuit, the output terminal of the signal access unit, and the input terminal of the signal transmission module. It is used to superimpose and amplify the signal to be tested and the DC bias compensation signal accessed by the signal access unit and output them as the signal to be transmitted to the signal transmission module.

[0024] Alternatively, the bias adjustment module includes a bias adjustment device, and the signal input selection unit includes an adder;

[0025] The bias adjustment device is connected to the DC measurement module and is used to generate a DC bias compensation signal based on the compensation parameters output by the DC measurement module.

[0026] The adder is connected to the output terminal of the bias adjustment device, the output terminal of the signal access unit, and the input terminal of the signal transmission module, respectively, and is used to superimpose the signal to be measured and the DC bias compensation signal accessed by the signal access unit and output them as the signal to be transmitted to the signal transmission module.

[0027] In one embodiment, the signal transmission system further includes a temperature detection unit connected to the DC measurement module; the temperature detection unit is positioned close to the signal transmission module and is used to acquire the real-time temperature of the signal transmission module.

[0028] The DC measurement module is also used to compare the real-time temperature output by the temperature detection unit with the reference temperature. When the difference between the real-time detected temperature and the reference temperature exceeds a preset range, the DC measurement module automatically reacquires the compensation parameters. The reference temperature is the temperature at the time of the most recent acquisition of the compensation parameters.

[0029] Alternatively, the DC measurement module is also used to output a prompt message to remind the user to reacquire the compensation parameters, and to use the temperature at the time of reacquiring the compensation parameters as the new reference temperature.

[0030] In one embodiment, the temperature detection unit includes a first temperature detection device and a second temperature detection device, which are respectively connected to the DC measurement module;

[0031] The first temperature detection device is positioned close to the electro-optical conversion unit in the signal transmission module, and is used to detect the ambient temperature of the electro-optical conversion unit as a first temperature signal, and send the first temperature signal to the DC measurement module;

[0032] The second temperature detection device is positioned close to the photoelectric conversion unit in the signal transmission module, and is used to detect the ambient temperature of the photoelectric conversion unit as a second temperature signal, and send the second temperature signal to the DC measurement module;

[0033] The DC measurement module determines whether to reacquire compensation parameters based on the first temperature signal and the second temperature signal.

[0034] In one embodiment, the signal transmission system further includes a gain flattening adjustment unit, which includes a comparison unit, an adjustable resistor, and a controller. The two input terminals of the comparison unit are respectively connected to the output terminal of the signal transmission module and a reference source with preset electrical parameters. The output terminal of the comparison unit is connected to the controller and is used to compare the signal output by the signal transmission module with the reference voltage output by the reference source, and output the comparison result to the controller.

[0035] The controller compares the comparison result with a pre-generated voltage difference list and generates a control signal based on the comparison result. The two ends of the adjustable resistor are respectively connected to the output terminal of the signal transmission module and the output terminal of the signal output module. Its control terminal is connected to the controller and is used to adjust the resistance value according to the control signal output by the controller, thereby adjusting the amplitude of the output signal of the signal transmission module.

[0036] According to a second aspect, one embodiment provides a signal transmission method for high-voltage circuit testing, applied to a signal transmission system, the signal transmission system including a signal input module, a signal transmission module, a signal output module, a bias adjustment module, and a DC measurement module; the signal transmission method includes a calibration stage and a measurement stage;

[0037] The calibration phase includes:

[0038] The signal input module receives the calibration signal and uses the calibration signal as the original transmission signal.

[0039] The DC measurement module is used to detect the DC bias loss during the transmission of the original transmitted signal through the signal transmission module;

[0040] The DC measurement module obtains compensation parameters based on the DC bias loss and controls the bias adjustment module to generate a DC bias compensation signal based on the compensation parameters.

[0041] The measurement phase includes:

[0042] The signal input module receives the test signal from an external device and uses the test signal as the original transmission signal.

[0043] The bias adjustment module outputs the DC bias compensation signal;

[0044] The original transmission signal is compensated using the DC bias compensation signal, and the compensated original transmission signal is output as a test acquisition signal to the signal transmission module so that the test acquisition signal output by the signal output module after electro-optical-electrical conversion and transmission is consistent with the DC bias voltage of the original transmission signal.

[0045] The signal output module outputs the signal transmitted by the signal transmission module.

[0046] In one embodiment, the DC measurement module obtains compensation parameters based on the DC bias loss, and controls the bias adjustment module to generate a DC bias compensation signal based on the compensation parameters, including:

[0047] The DC measurement module detects the first voltage signal at the input terminal of the signal transmission module and the second voltage signal at the output terminal of the signal transmission module;

[0048] Calculate the first difference between the first voltage signal and the second voltage signal to obtain the initial compensation parameters;

[0049] The initial compensation parameters are sent to the bias adjustment module for initial configuration.

[0050] The bias adjustment module generates a first bias voltage based on the initial compensation parameters;

[0051] The original transmitted signal is compensated using the first bias voltage;

[0052] The compensated input signal is output to the signal transmission module for electro-optical-electrical transmission.

[0053] The DC measurement module detects the compensated input signal and outputs the second voltage signal via the signal transmission module;

[0054] Calculate the second difference between the DC bias voltage of the compensated second voltage signal and the DC bias voltage of the original transmitted signal;

[0055] Determine if the second difference is equal to 0. If it is, stop the following steps and complete the calibration phase; otherwise, proceed with the following steps.

[0056] The fine-tuning compensation parameters are obtained based on the second difference;

[0057] The fine-tuning compensation parameters are sent to the bias adjustment module, which then superimposes the fine-tuning compensation parameters and the initial compensation parameters to generate a second bias voltage.

[0058] The original transmitted signal is compensated using the second bias voltage;

[0059] The compensated original transmission signal is output to the signal transmission module for electro-optical-electrical transmission.

[0060] In one embodiment, the signal transmission system further includes a temperature detection unit, and the signal transmission method further includes:

[0061] The ambient temperature in the signal transmission module is monitored to obtain the real-time temperature of the signal transmission module;

[0062] The DC measurement module compares the real-time temperature output by the temperature detection unit with the reference temperature, which is the temperature at the time of the most recent acquisition of compensation parameters.

[0063] When the difference between the real-time detected temperature and the reference temperature exceeds the preset range, the system automatically enters the calibration phase or outputs a prompt message to remind the user to re-enter the calibration phase, so that the DC measurement module can re-acquire the compensation parameters.

[0064] The temperature at which the compensation parameters are reacquired will be used as the new reference temperature.

[0065] When the difference between the real-time detected temperature and the reference temperature does not exceed the preset range, the bias adjustment module maintains the second bias voltage unchanged.

[0066] According to the signal transmission system of the above embodiment, since the original transmission signal is supplemented by gain at the front end of the signal transmission, the output signal of the signal output module is consistent with the original transmission signal of the input signal transmission system. The simplified calibration mechanism replaces the existing complicated high and low frequency separation calibration process, thereby achieving accurate compensation for DC bias and gain changes throughout the entire link, ensuring the accuracy and efficiency of the signal transmission system. Attached Figure Description

[0067] Figure 1 This is a functional structure diagram of a signal transmission system according to one embodiment;

[0068] Figure 2 This is a functional structure diagram of a signal transmission system according to another embodiment;

[0069] Figure 3 This is a schematic diagram of the circuit connection of the bias adjustment module in one embodiment;

[0070] Figure 4 This is a circuit connection diagram of a signal input selection unit in one embodiment;

[0071] Figure 5 This is a schematic diagram of the circuit connection of the first temperature detection device in one embodiment;

[0072] Figure 6 This is a schematic diagram of the circuit connection of the electro-optic conversion unit in one embodiment;

[0073] Figure 7 This is a schematic diagram of the circuit connection of the photoelectric conversion unit in one embodiment;

[0074] Figure 8 This is a schematic diagram of the circuit connection of the gain flattening adjustment unit in one embodiment;

[0075] Figure 9 This is a flowchart illustrating a signal transmission method in one embodiment;

[0076] Figure 10 This is a schematic diagram of the process for acquiring the DC bias compensation signal in one embodiment;

[0077] Figure 11 This is a schematic diagram of the DC bias calibration process in one embodiment;

[0078] Figure 12 This is an example diagram illustrating the fitting and correction process for the calibration of the signal transmission module in one embodiment. Detailed Implementation

[0079] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0080] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0081] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this invention, unless otherwise specified, include both direct and indirect connections (linkages).

[0082] Currently, fiber optic isolation transmission technology applied to high-voltage testing scenarios in power electronics faces the following technical challenges:

[0083] 1) The complexity of the existing high- and low-frequency separation calibration architecture.

[0084] In existing optical transmission systems for high-voltage circuit testing, to ensure accurate transmission of both high and low frequency signals, a common approach is to first separate the electrical signal into high-frequency and low-frequency components, and then perform "electro-optical-electro-transmission" on each of the high-frequency and low-frequency paths separately. For this architecture, existing calibration mechanisms require independent operation based on the high- and low-frequency separation system. On the one hand, calibration is needed separately for the offset introduced by temperature drift in the high-frequency transmission path. The calibration process requires separate acquisition, analysis, and compensation of the separated high-frequency signal, making the operation relatively cumbersome and time-consuming. On the other hand, the calibration processes for the high- and low-frequency paths are independent, requiring separate setup and configuration of different parameters for the calibration test environment, which also presents a relatively cumbersome operational challenge, resulting in a lack of uniformity in the entire calibration process.

[0085] 2) Signal distortion problem caused by inherent DC bias in optoelectronic devices.

[0086] In the "electro-optical-electro-transmission" link, optical emitting devices (such as lasers) and optical receiving devices (such as photodiodes) are the core conversion elements. Their inherent characteristics introduce additional DC bias during signal transmission. Specifically, the dark current and other related parameters of lasers and photodiodes drift with changes in temperature and operating time. Consequently, during the conversion of electrical signals into optical signals and then back into electrical signals, these drifts are superimposed on the original signal, indirectly affecting the operating state of active devices in the signal link. For example, they can affect the static operating point, which in turn affects the accuracy and reliability of test and measurement results.

[0087] 3) Real-time calibration of end-to-end gain variation.

[0088] Existing calibration schemes mostly focus on local error compensation in the high-frequency path (such as temperature drift), lacking real-time global gain calibration for the entire "electro-optical-electro" transmission link. During signal transmission, the conversion efficiency of optoelectronic devices, fiber transmission loss, and gain characteristics of amplifier circuits all dynamically change with factors such as device aging and temperature variations, leading to fluctuations in the overall gain of the transmission link. This gain variation across the entire link disrupts the proportional relationship between high-frequency and low-frequency signals. Especially in high-voltage circuit testing environments, even slight signal gain fluctuations can be amplified into significant measurement errors, failing to accurately reproduce the true signal characteristics of the circuit. Existing calibration mechanisms cannot provide unified, real-time calibration compensation for the overall gain of the link, limiting the long-term stability of the test and measurement system. Therefore, a comprehensive real-time calibration technology is needed that can integrate the entire transmission process, simplify calibration steps, and ensure long-term stability.

[0089] This application provides a signal transmission method for test signal acquisition. It optimizes and improves the existing calibration scheme to address issues such as DC bias drift induced by dark current of optoelectronic devices and signal distortion caused by temperature drift in high-voltage power electronics testing scenarios, as well as the problems of cumbersome process, insufficient stability, complex architecture and easy signal loss in existing calibration schemes. This improves the signal transmission accuracy, long-term operational stability and engineering implementation convenience of fiber optic isolated transmission in high-voltage testing scenarios, and meets the application requirements of accurate, safe and reliable signal transmission in the field of high-voltage power electronics testing.

[0090] Example 1:

[0091] Please refer to Figure 1This is a functional structure diagram of a signal transmission system according to one embodiment, used for signal transmission in high-voltage circuit testing. The signal transmission system includes a signal input module 1, a signal transmission module 2, a signal output module 3, a bias adjustment module 4, and a DC measurement module 5. The signal input module 1 is used to receive the original transmission signal. The bias adjustment module 4 is connected to both the signal input module 1 and the DC measurement module 5, and is used to receive compensation parameters output by the DC measurement module 5, and generate a DC bias compensation signal Vctr1 based on the compensation parameters. The signal input module 1 is also used to compensate the original transmission signal using the DC bias compensation signal Vctr1, and output the compensated original transmission signal as the signal to be transmitted to the signal transmission module 2. The signal transmission module 2 is used to first modulate the signal to be transmitted from an electrical signal into an optical signal, and then demodulate the optical signal transmitted through optical fiber back into an electrical signal. The DC measurement module 5 is used to detect the DC bias loss of the signal to be transmitted during the transmission process of the signal transmission module 2, obtain the corresponding compensation parameters for the DC bias loss, and send the compensation parameters to the bias adjustment module 4. The bias adjustment module 4 then generates a DC bias compensation signal Vctr1 according to the compensation parameters, ensuring that the signal output by the signal transmission module 2 matches the DC bias voltage of the original transmitted signal input to the signal input module 1. The signal output module 3 is used to output the original transmitted signal of the demodulated return signal.

[0092] In one embodiment, the original transmitted signal is a calibration signal V2 during the calibration phase and a test signal V2 acquired by an external testing device during the testing phase. The DC measurement module 5 is connected to the input and output terminals of the signal transmission module 2, respectively, and is used to detect the first voltage signal DC1 at the input terminal of the signal transmission module 2 and the second voltage signal DC2 at the output terminal of the signal transmission module 2.

[0093] During the calibration phase, signal input module 1 inputs calibration signal V2. DC measurement module 5 obtains initial compensation parameters based on the first difference between the detected first voltage signal DC1 and the second voltage signal DC2, and sends these initial compensation parameters to bias adjustment module 4 for initial configuration. Bias adjustment module 4 generates a first bias voltage based on the initial compensation parameters and uses this first bias voltage to compensate for the calibration signal V2. The compensated calibration signal is then output to signal transmission module 2. DC measurement module 5 detects the second voltage signal after the compensated calibration signal is transmitted through signal transmission module 2, calculates the second difference between the compensated second voltage signal and the calibration signal V2 to obtain fine-tuning compensation parameters, and sends these parameters to bias adjustment module 4. Bias adjustment module 4 superimposes the fine-tuning compensation parameters and the initial compensation parameters to generate a second bias voltage, and uses this second bias voltage to compensate for the original transmitted signal. DC measurement module 5 continuously calculates the second difference until it is less than a preset threshold, where the preset threshold includes 0.

[0094] During the testing phase, the signal input module 1 inputs the test signal V1 from the external test equipment, and the bias adjustment module 4 uses a second bias voltage corresponding to the second difference within a preset threshold to compensate the test signal V1, and outputs the compensated test signal as the signal to be transmitted to the signal transmission module 2.

[0095] Please refer to Figure 2 The diagram below illustrates the functional structure of a signal transmission system according to another embodiment. In one embodiment, the signal input module 1 includes a signal access unit 11, a standard signal generation unit 12, and a signal input selection unit 13. The signal access unit 11 is used to access the test signal V1 acquired by an external testing device. The standard signal generation unit 12 is used to generate a calibration signal V2 with preset electrical parameters. The signal input selection unit 13 is connected to both the signal access unit 11 and the standard signal generation unit 12. During the calibration phase, the standard signal generation unit 12 is activated to use the calibration signal V1 as the original transmission signal. During the testing phase, the signal access unit 11 is activated to use the test signal V1 as the original transmission signal.

[0096] Please refer to Figure 3 This is a circuit connection diagram of the bias adjustment module in one embodiment. In one embodiment, the bias adjustment module 4 includes a bias adjustment device 41 and a bias amplifier circuit 42. The bias adjustment device 41 is connected to the DC measurement module 5 and is used to generate a bias voltage according to the compensation parameters output by the DC measurement module 5. The bias amplifier circuit 42 is used to amplify the bias voltage and output it as a DC bias compensation signal Vctr1 to the signal input selection unit 13. The bias amplifier circuit 42 includes a first amplifier U1, a first resistor R1, and a second resistor R2. The positive input terminal of the first amplifier U1 is connected to the bias adjustment device 41 and is used for the input of the bias voltage. One end of the first resistor R1 is grounded, and the other end is connected to the negative input terminal of the first amplifier U1. One end of the second resistor R2 is connected to the negative input terminal of the first amplifier U1, and the other end is connected to the output terminal of the first amplifier U1.

[0097] In one embodiment, the signal input selection unit 13 includes a transmission signal amplification circuit. This transmission signal amplification circuit is connected to the output of the bias amplification circuit 42 and the output of the signal access unit 11, and is used to superimpose and amplify the test signal V1 and the DC bias compensation signal Vctr1 received by the signal access unit 11. The output of the transmission signal amplification circuit is connected to the input of the signal transmission module 2. In another embodiment, the transmission signal amplification circuit includes a second amplifier U2, a third resistor R3, and a fourth resistor R4. The positive input of the second amplifier U2 is connected to the output of the bias amplification circuit 42 and the signal access unit 11, and the output of the second amplifier U2 is connected to the signal transmission module 2. One end of the fourth resistor R4 is grounded, and the other end is connected to the negative input of the second amplifier U2. One end of the third resistor R3 is connected to the negative input of the second amplifier U2, and the other end is connected to the output of the second amplifier U2.

[0098] Please refer to Figure 4 This is a circuit connection diagram of the signal input selection unit in one embodiment. In one embodiment, the bias adjustment module 4 includes a bias adjustment device 41, and the signal input selection unit 13 includes an adder. The bias adjustment device 41 is connected to the DC measurement module 5 and is used to generate a DC bias compensation signal Vctr1 based on the compensation parameters output by the DC measurement module 5. The input terminal of the adder is connected to the output terminal of the bias adjustment device 41 and the output terminal of the signal access unit 11, respectively, and is used to superimpose the test signal V1 and the DC bias compensation signal Vctr1 received by the signal access unit 11. The output terminal of the adder is connected to the input terminal of the signal transmission module 2. In one embodiment, the adder includes a third amplifier U3. The positive input terminal of the third amplifier U3 is connected to the output terminal of the signal access unit 11, and the negative input terminal of the third amplifier U3 is connected to the output terminal of the bias adjustment device 41.

[0099] like Figure 2 As shown, in one embodiment, the signal transmission system further includes a temperature detection unit 6 connected to the DC measurement module 5. The temperature detection unit 6 is positioned close to the signal transmission module 2 and is used to acquire the real-time temperature of the signal transmission module 2. The DC measurement module 5 is also used to compare the real-time temperature output by the temperature detection unit 6 with a reference temperature. When the difference between the real-time detected temperature and the reference temperature exceeds a preset range, the DC measurement module 5 automatically reacquires compensation parameters, wherein the reference temperature is the temperature at the time of the most recent acquisition of compensation parameters. In one embodiment, the DC measurement module 5 is also used to output a prompt message to the user to reacquire compensation parameters, and after reacquiring the compensation parameters, uses the temperature at the time of reacquiring the compensation parameters as the new reference temperature.

[0100] In one embodiment, the temperature detection unit 6 includes a first temperature detection device 61 and a second temperature detection device 62, respectively connected to the DC measurement module 5. The first temperature detection device 61 is disposed near the electro-optical conversion unit 21 in the signal transmission module 2, and is used to detect the ambient temperature of the electro-optical conversion unit 21 as a first temperature signal, and send the first temperature signal to the DC measurement module 5. The second temperature detection device 62 is disposed near the photoelectric conversion unit 23 in the signal transmission module 2, and is used to detect the ambient temperature of the photoelectric conversion unit 23 as a second temperature signal, and send the second temperature signal to the DC measurement module 5. The DC measurement module 5 is further used to determine whether to reacquire compensation parameters based on the first and second temperature signals.

[0101] Please refer to Figure 5 This is a circuit connection diagram of the first temperature detection device in one embodiment. In one embodiment, the circuit structures of the first temperature detection device and the second temperature monitoring device are the same, each including a first temperature control amplifier UT1, a temperature control resistor RT, and a grounding resistor Rt0. The output terminal of the first temperature control amplifier UT1 is connected to a temperature drift conversion device. One end of the temperature control resistor RT is used for the input of a working voltage VCC, and the other end is connected to the positive input terminal of the first temperature control amplifier UT1. One end of the grounding resistor Rt0 is grounded, and the other end is connected to the positive input terminal of the first temperature control amplifier UT1. The negative input terminal of the first temperature control amplifier UT1 is used for the input of a preset reference voltage Vref. In one embodiment, the NTC resistor (temperature control resistor RT) and the grounding resistor Rt0 are connected in series to form a voltage divider circuit. Utilizing the characteristic that the resistance value of the NTC resistor is sensitive to temperature and changes with temperature, a correspondence between the output voltage after voltage division and the temperature is established. The voltage division value and the reference voltage Vref are input to an operational amplifier or comparator to obtain the output result.

[0102] like Figure 1 As shown, in one embodiment, the signal transmission module 2 includes an electro-optical conversion unit 21, an optical fiber 22, and a photoelectric conversion unit 23. The electro-optical conversion unit 21 is used to modulate an electrical signal into an optical signal, the optical fiber 22 is used to transmit the optical signal, and the photoelectric conversion unit 23 is used to demodulate the optical signal into an electrical signal.

[0103] Please refer to Figure 6 The diagram below shows the circuit connection of an electro-optic conversion unit 21 in one embodiment. The electro-optic conversion unit 21 includes a first electro-optic diode D1 and a first voltage divider resistor Rv1. One end of the first electro-optic diode D1 is connected to the signal input module 1, and the other end is connected to one end of the first voltage divider resistor Rv1. The other end of the first voltage divider resistor Rv1 is connected to the reference ground VEE.

[0104] Please refer to Figure 7The diagram below shows the circuit connection of a photoelectric conversion unit 23 in one embodiment. The photoelectric conversion unit 23 includes a first photodiode D2 and a second voltage divider resistor Rv2. One end of the first photodiode D2 is used for the input of the operating voltage VCC1, and the other end is connected to the signal output module 3. One end of the second voltage divider resistor Rv2 is connected to the reference ground VEE.

[0105] Please refer to Figure 8 This is a circuit connection diagram of the gain flattening adjustment unit in one embodiment. In one embodiment, the signal transmission system further includes a gain flattening adjustment unit 7, which includes a comparison unit 71, an adjustable resistor Rv, and a controller 72. The two input terminals of the comparison unit 71 are respectively connected to the output terminal of the signal transmission module 2 and a reference source with preset electrical parameters. The output terminal of the comparison unit 71 is connected to the controller 72, used to compare the signal output by the signal transmission module 2 with the reference voltage output by the reference source, and output the comparison result to the controller 72. The controller 72 compares the comparison result with a pre-generated voltage difference list and generates a control signal based on the comparison result. The two ends of the adjustable resistor Rv are respectively connected to the output terminal of the signal transmission module 2 and the output terminal of the signal output module 3, and its control terminal is connected to the controller 72, used to adjust the resistance value according to the control signal output by the controller 72, thereby adjusting the amplitude of the output signal of the signal transmission module 2. In one embodiment, the function of the controller 72 can be implemented by the control processor of the DC measurement module 5.

[0106] In one embodiment, the signal output module 3 is further used to perform power detection and gain adjustment on the output signal. The signal output module 3 includes a signal output unit 32, a power detection unit 33, and an amplitude calibration unit 34. The signal output unit 32 is used to output the original transmitted signal or the original transmitted signal after gain adjustment, and serves as the output of the signal transmission system. The power detection unit 33 is connected to the output terminal of the signal output unit 32 and is used to detect the electrical power parameter of the original transmitted signal. The amplitude calibration unit 34 is used to detect the electrical amplitude parameter of the original transmitted signal.

[0107] One embodiment of this application also discloses a signal transmission method, please refer to... Figure 9 This is a flowchart illustrating a signal transmission method in one embodiment. The signal transmission method is applied to the signal transmission system described above and includes:

[0108] Step 101: Begin the calibration phase.

[0109] During the calibration phase, the signal input module receives the calibration signal and outputs the calibration signal as the raw transmission signal to the signal transmission module.

[0110] Step 102: Detect and calibrate DC bias loss.

[0111] The DC measurement module is used to detect the DC bias loss during the transmission of the original transmitted signal through the signal transmission module.

[0112] Step 103: Obtain calibration compensation parameters.

[0113] The DC measurement module obtains compensation parameters based on the DC bias loss.

[0114] Step 104: Iterate through the process to obtain the calibration DC bias compensation signal.

[0115] The bias control module generates a DC bias compensation signal based on the compensation parameters. Please refer to [reference needed]. Figure 10 This is a schematic diagram of the process for acquiring a DC bias compensation signal in one embodiment, including:

[0116] Step 301: Obtain the first and second voltage signals.

[0117] The DC measurement module detects the first voltage signal at the input of the signal transmission module and the second voltage signal at the output of the signal transmission module.

[0118] Step 302: Obtain compensation parameters.

[0119] Calculate the first difference between the first voltage signal and the second voltage signal to obtain the initial compensation parameters.

[0120] Step 303: Output the first bias voltage.

[0121] The initial compensation parameters are sent to the bias adjustment module to perform initial configuration. The bias adjustment module generates the first bias voltage based on the initial compensation parameters.

[0122] Step 304: Reacquire the first and second voltage signals.

[0123] The original transmitted signal is compensated using a first bias voltage, and the compensated input signal is output to the signal transmission module for electro-optical-electrical transmission. The DC measurement module detects the second voltage signal output by the signal transmission module from the compensated input signal.

[0124] Step 305: Determine whether the difference is less than the preset value.

[0125] Calculate the second difference between the DC bias voltage of the compensated second voltage signal and the DC bias voltage of the original transmitted signal. Determine if the second difference is equal to 0. If it is, execute step 306 to end the calibration, then stop executing the following steps and complete the calibration phase; otherwise, execute the following steps:

[0126] Step 307: Overlay compensation parameters.

[0127] The fine-tuning compensation parameters are obtained based on the second difference. These parameters are then sent to the bias adjustment module.

[0128] Step 308: Output the second bias voltage.

[0129] The bias adjustment module superimposes the fine-tuning compensation parameters and the initial compensation parameters to generate a second bias voltage. This second bias voltage is used to compensate the original transmitted signal. The compensated original transmitted signal is then output to the signal transmission module for electro-optical-electrical transmission. Steps 304, 305, 307, and 308 are repeated until step 306 can be reached, thus ending the calibration phase.

[0130] After the calibration phase is completed, proceed to step 105 to perform the measurement phase.

[0131] The signal input module receives the signal to be tested from an external device and uses the signal to be tested as the original transmission signal.

[0132] Step 106: Output the calibration DC bias compensation signal.

[0133] The bias adjustment module outputs the DC bias compensation signal obtained during the calibration phase, and uses the DC bias compensation signal to compensate the original transmitted signal.

[0134] Step 107: The signal transmission system outputs a signal.

[0135] The compensated original transmitted signal is output as the test acquisition signal to the signal transmission module, ensuring that the test acquisition signal output by the signal output module after electro-optical-electrical conversion and transmission has the same DC bias voltage as the original transmitted signal. The signal output module then outputs the signal transmitted by the signal transmission module.

[0136] In one embodiment, step 201, which performs temperature monitoring, is executed simultaneously with step 105.

[0137] The ambient temperature in the signal transmission module is monitored to obtain the real-time temperature of the signal transmission module.

[0138] Step 202: Obtain the temperature difference value.

[0139] The DC measurement module compares the real-time temperature output by the temperature detection unit with the reference temperature, which is the temperature at the time of the most recent acquisition of compensation parameters.

[0140] Step 203: Determine whether the difference is greater than the preset threshold.

[0141] When the difference between the real-time detected temperature and the reference temperature exceeds a preset range, step 101 is automatically executed, either entering the calibration phase or outputting a prompt message to remind the user to re-enter the calibration phase, so that the DC measurement module can reacquire the compensation parameters. In one embodiment, the temperature at which the compensation parameters are reacquired is used as the new reference temperature.

[0142] When the difference between the real-time detected temperature and the reference temperature does not exceed the preset range, the bias adjustment module maintains the second bias voltage unchanged.

[0143] During fiber optic transmission, due to the inherent properties of the optoelectronic devices used, there will be a phenomenon where the output signal deviates from the actual input signal due to the influence of temperature and time. Currently, the common technology uses high-frequency and low-frequency separation for electro-optical conversion, and then performs independent calibration after optical-electric conversion, which is a relatively complicated process.

[0144] Dark current is an inherent noise source in semiconductor devices, specifically manifested as an additional DC bias superimposed on the transmission system. This DC bias signal is primarily contributed by lasers and photodiodes. The dark current in lasers mainly originates from carrier leakage and thermally excited leakage, while the dark current in photodiodes mainly originates from diffusion current and surface leakage current. This leakage current reduces sensitivity, increases noise, and degrades the signal-to-noise ratio. Changes in dark current in the circuit system ultimately lead to changes in the DC bias of the signal transmission system. When the signal transmission system uses separate high-frequency and low-frequency transmission, the impact of dark current is directly reflected in the low-frequency transmission path. Dark current and temperature are positively correlated.

[0145] Idark~Tm×exp(-Eg / (kT));

[0146] Where T is the absolute temperature, Eg is the bandgap temperature of the material, k is the Boltzmann constant, and m is an empirical coefficient.

[0147] Since the dark current of optoelectronic devices can cause DC offset, and the dark current is greatly affected by temperature, it is necessary to periodically detect the device temperature and perform real-time calibration for DC offset. Currently, there is a lack of real-time calibration schemes that integrate the entire process and take into account long-term stability.

[0148] In related technologies, signal transmission typically employs a combination of low-pass and high-pass filters in the circuit to separate the input signal into high-frequency and low-frequency signals, which are then transmitted separately. At the receiving end, the signals are combined and amplitude calibrated. Alternatively, a high-pass filter separates the signal at the input, allowing the high-frequency signal to undergo voltage-to-current conversion for transmission. The low-frequency signal is then separated by subtracting the input signal from the high-frequency signal. The characteristics of a transistor differential circuit and operational amplifier are then utilized to suppress the VBE temperature drift of the open-loop linear converter transistor using a low-frequency voltage, thus achieving signal transmission temperature drift calibration. These methods are prone to signal loss or overlap and require matching of high-pass and low-pass filters, making implementation relatively complex and difficult.

[0149] The signal transmission system for high-voltage circuit testing disclosed in this application includes a signal input module, a signal transmission module, a signal output module, a bias adjustment module, and a DC measurement module. The signal input module receives the original transmitted signal. The bias adjustment module generates a DC bias compensation signal based on the compensation parameters output by the DC measurement module. The original transmitted signal is compensated using the DC bias compensation signal, and the compensated original transmitted signal is output to the signal transmission module as the signal to be transmitted. The signal transmission module transmits the signal to be transmitted using optical fiber. The DC measurement module obtains compensation parameters by detecting the DC bias loss during transmission in the signal transmission module. The signal output module outputs the original transmitted signal. Because the test acquisition signal is gain-supplemented at the front end of the signal transmission, the electrical parameters of the test acquisition signal output by the signal output module are consistent with those of the original acquired test acquisition signal. This simplifies the calibration mechanism and replaces the existing complex high- and low-frequency separate calibration process, thereby achieving accurate compensation for DC bias and gain variations across the entire link and ensuring the accuracy and efficiency of signal transmission in the test and measurement circuit.

[0150] To facilitate understanding of the application of the signal transmission method in the embodiments of this application, the following specific embodiments are described, including:

[0151] In one embodiment, the control processor of the DC measurement module is an MCU microcontroller, a programmable logic device (FPGA or CPLD, etc.), an ARM processor, or a digital signal processor (DSP), integrating analog-to-digital conversion (ADC) and digital-to-analog conversion (DAC) functions. The signal input module receives the test acquisition signal V0 and generates a first verification signal V1 by a calibration signal generation device (standard signal generation unit). The calibration signal generation device includes a configurable ADC, MCU, FPGA, CPLD, ARM, or DSP. The bias adjustment module includes a configurable ADC, MCU, FPGA, CPLD, ARM, or DSP. The control processor of the DC measurement module is an MCU microcontroller, a programmable logic device (FPGA or CPLD, etc.), an ARM processor, or a DSP. Figure 3 , Figure 5 , Figure 6 and Figure 7 The diagram shows a signal input selection unit, a temperature detection device, an electro-optical conversion unit, and a photoelectric conversion unit. The signal output module includes a power detection unit and an amplitude detection unit.

[0152] Please refer to Figure 11 This is a schematic diagram of a DC bias calibration process in one embodiment, including:

[0153] Step 401: Select the input signal.

[0154] The signal input selection unit selects the input signal to determine whether the test acquisition signal V0 or the generated first verification signal V1 will enter the subsequent transmission.

[0155] Step 402: Configure the bias adjustment module.

[0156] The DC measurement module configures the bias adjustment module, which generates an initial voltage value Vctrl1. After adjusting the initial value of the input signal, it proceeds to subsequent transmission.

[0157] Step 403: Measure the bias value.

[0158] The DC measurement module measures two key bias values: one is the electrical signal bias value entering the electro-optical conversion stage, denoted as DC1, and the other is the electrical signal bias value output after photoelectric conversion, denoted as DC2.

[0159] Step 404: Calculate the change in bias.

[0160] The DC bias introduced by the signal transmission module is calculated, and the output calculation result is recorded as ΔDC. Based on ΔDC, a bias value needs to be added to the bias adjustment device relative to the initial bias value. The corresponding code value is obtained according to the target bias voltage and written to the register. At this time, the output voltage value Vctrl2 of the bias adjustment device is amplified or attenuated by the first amplifier U1 and then superimposed with the original signal. After being amplified or attenuated by the second amplifier U2, the voltage signal is then transmitted through the link.

[0161] Step 405, repeat the measurement.

[0162] The DC test system measures the DC bias value of the signal before and after passing through the transmission system. The above steps are repeated until the value of ΔDC is 0.

[0163] Step 406, Temperature Monitoring.

[0164] The first and second temperature detection devices monitor the ambient temperature of the optoelectronic device in real time, and periodically report the device temperature to the DC test system at a time interval of T. When the temperature differs from the ambient temperature in the above steps by more than ±a℃, the above steps are repeated to repeatedly calibrate the DC bias.

[0165] Step 407, gain fine-tuning.

[0166] After eliminating DC offset through the aforementioned steps, the electrical signal recovered by the optoelectronic device is transmitted to the subsequent transmission link. Due to the combined effects of various factors such as the photoelectric conversion efficiency of the optoelectronic device, signal loss during fiber optic transmission, and the gain characteristics of the amplifier circuit, the recovered electrical signal suffers from a technical problem of gain unevenness within the frequency band. The voltage reference signal and the electrical signal recovered by the optoelectronic device are input into a comparison unit for calculation, and the output result is transmitted to the controller. The controller adaptively adjusts the signal gain in the terminal transmission link to achieve gain flattening within the frequency band of the electrical signal, thus ensuring signal transmission quality.

[0167] Step 408, Signal transmission module calibration.

[0168] In one embodiment, a high-precision configurable digital-to-analog converter or an extension module in a programmable logic device that can output adjustable digital signals is selected as the bias adjustment device of this signal transmission system.

[0169] First, the bias adjustment device is initially calibrated. This initial calibration is achieved by configuring the device's code value through the controller. Assuming the input voltage of the bias adjustment device is V1 and the full-scale voltage corresponding to the input range of the transmission system is V2, the controller's configured code value satisfies the formula: code = 2^(accuracy) * V1 / V2. During the adjustment process, the measured DC bias value DC7 is made 0V, thereby obtaining the corresponding numerical relationship between the equivalent source terminal voltage value of the bias adjustment device and the controller's configured code value.

[0170] Secondly, due to the presence of dark current in optoelectronic devices, a DC bias is introduced into the signal transmission system. At this time, the measured DC bias value DC8 ≠ 0V. The controller calculates the DC bias deviation value △DC based on the measured DC8. In order to make the DC bias at the final output of the system reach 0V, the configuration code value of the bias adjustment device is reconfigured according to the aforementioned correspondence between the voltage value of the bias adjustment device and the controller code value. The DC bias value introduced by the signal transmission system is corrected through this reconfiguration operation.

[0171] The relationship between the signal y received at the output terminal and the input signal is:

[0172] y = ax + b;

[0173] Where x is the input signal, slope a is the gain introduced by the transmission link, and intercept b is the DC offset introduced by the transmission system.

[0174] Please refer to Figure 12 The diagram illustrates the fitting and correction process for the calibration of the signal transmission module in one embodiment. For the calibration of the slope a, the actual input signals are configured as A1, B1, C1, D1, and E1 by adjusting the bias device, and the corresponding signals measured at the output terminal are A, B, C, D, and E.

[0175] The signals A, B, C, D, and E measured at the output terminal are fitted to obtain the corresponding scaling coefficients for amplifying or reducing the input signals. Based on these scaling coefficients, the input signals A1, B1, C1, D1, and E1 are calibrated to obtain the corrected signals A', B', C', D', and E'.

[0176] Finally, to eliminate the stability risks caused by changes in time and temperature, the temperature of the transmission system is periodically monitored by a temperature measurement system composed of temperature sensors or NTC resistors, and the above steps are repeated.

[0177] In the above embodiments, implementation can be achieved, in whole or in part, by software, hardware, firmware, or any combination thereof. Furthermore, as those skilled in the art will understand, the principles herein can be reflected in a computer program product on a computer-readable storage medium pre-loaded with computer-readable program code. Any tangible, non-transitory computer-readable storage medium may be used, including magnetic storage devices (hard disks, floppy disks, etc.), optical storage devices (CDs, DVDs, Blu-ray discs, etc.), flash memory, and / or the like. These computer program instructions can be loaded onto a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to form a machine, such that instructions executing on the computer or other programmable data processing apparatus can generate means for performing a specified function. These computer program instructions can also be stored in a computer-readable storage medium that can instruct the computer or other programmable data processing apparatus to operate in a particular manner, such that instructions stored in the computer-readable storage medium can form an article of manufacture, including means for implementing the specified function. The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to perform a series of operational steps on the computer or other programmable apparatus to produce a computer-implemented process, such that instructions executing on the computer or other programmable apparatus can provide steps for implementing the specified function.

[0178] This document describes various exemplary embodiments with reference to them. However, those skilled in the art will recognize that changes and modifications can be made to the exemplary embodiments without departing from the scope of this document. For example, various operational steps and components for performing operational steps can be implemented in different ways depending on the specific application or considering any number of cost functions associated with the operation of the system (e.g., one or more steps can be deleted, modified, or combined with other steps).

[0179] While the principles herein have been illustrated in various embodiments, numerous modifications to the structures, arrangements, proportions, elements, materials, and components, particularly suited to specific environments and operational requirements, may be used without departing from the principles and scope of this disclosure. These modifications and other alterations or alterations will be included within the scope of this document. Those skilled in the art will recognize that many changes can be made to the details of the above embodiments without departing from the fundamental principles of the invention.

Claims

1. A signal transmission system for high-voltage circuit testing, characterized in that, It includes a signal input module, a signal transmission module, a signal output module, a bias adjustment module, and a DC measurement module; The signal input module is used to receive the original transmission signal; The bias adjustment module is connected to the signal input module and the DC measurement module respectively, and is used to receive the compensation parameters output by the DC measurement module and generate a DC bias compensation signal based on the compensation parameters. The signal input module is also used to compensate the original transmission signal with the DC bias compensation signal, and output the compensated original transmission signal as the signal to be transmitted to the signal transmission module. The signal transmission module is used to first modulate the signal to be transmitted from an electrical signal into an optical signal, and then demodulate the optical signal transmitted through the optical fiber back into an electrical signal. The DC measurement module is used to detect the DC bias loss of the signal to be transmitted during the transmission process of the signal transmission module, obtain the compensation parameters corresponding to the DC bias loss, and send the compensation parameters to the bias adjustment module so that the bias adjustment module generates a DC bias compensation signal according to the compensation parameters, so that the signal output by the signal transmission module is consistent with the DC bias voltage of the original transmission signal connected to the signal input module. The signal output module is used to output the original transmitted signal of the demodulated return signal; The original transmission signal is a calibration signal during the calibration phase and a test signal collected by external testing equipment during the testing phase. The DC measurement module is connected to the input and output terminals of the signal transmission module, respectively, and is used to detect the first voltage signal at the input terminal of the signal transmission module and the second voltage signal at the output terminal of the signal transmission module. During the calibration phase, the signal input module inputs a calibration signal, and the DC measurement module obtains an initial compensation parameter based on the first difference between the detected first voltage signal and the second voltage signal, and sends the initial compensation parameter to the bias adjustment module to perform initial configuration of the bias adjustment module. The bias adjustment module generates a first bias voltage based on the initial compensation parameters, and uses the first bias voltage to compensate the calibration signal. The compensated calibration signal is then output to the signal transmission module. The DC measurement module detects the second voltage signal after the compensated calibration signal is transmitted through the signal transmission module, calculates the second difference between the compensated second voltage signal and the calibration signal to obtain fine-tuning compensation parameters, and sends these parameters to the bias adjustment module. The bias adjustment module superimposes the fine-tuning compensation parameters and the initial compensation parameters to generate a second bias voltage, and uses this second bias voltage to compensate the original transmitted signal. The DC measurement module iteratively calculates the second difference until it is less than a preset threshold, where the preset threshold includes 0. During the testing phase, the signal input module inputs the test signal from the external test equipment, and the bias adjustment module uses a second bias voltage corresponding to the second difference within the preset threshold to compensate the test signal, and outputs the compensated test signal as the signal to be transmitted to the signal transmission module.

2. The signal transmission system as described in claim 1, characterized in that, The signal input module includes: The signal access unit is used to access the signal under test collected by external testing equipment; A standard signal generation unit is used to generate calibration signals with preset electrical parameters; The signal input selection unit is connected to both the signal access unit and the standard signal generation unit. It is used to turn on the standard signal generation unit during the calibration phase and use the calibration signal as the original transmission signal; and to turn on the signal access unit during the testing phase and use the signal under test as the original transmission signal.

3. The signal transmission system as described in claim 2, characterized in that, The bias adjustment module includes a bias adjustment device and a bias amplifier circuit; The bias adjustment device is connected to the DC measurement module and is used to generate a bias voltage based on the compensation parameters output by the DC measurement module. The signal input selection unit includes a transmission signal amplification circuit; The transmission signal amplification circuit is connected to the output terminal of the bias amplification circuit, the output terminal of the signal access unit, and the input terminal of the signal transmission module. It is used to superimpose and amplify the signal to be tested and the DC bias compensation signal accessed by the signal access unit and output them as the signal to be transmitted to the signal transmission module. Alternatively, the bias adjustment module includes a bias adjustment device, and the signal input selection unit includes an adder; The bias adjustment device is connected to the DC measurement module and is used to generate a DC bias compensation signal based on the compensation parameters output by the DC measurement module. The adder is connected to the output terminal of the bias adjustment device, the output terminal of the signal access unit, and the input terminal of the signal transmission module, respectively, and is used to superimpose the signal to be measured and the DC bias compensation signal accessed by the signal access unit and output them as the signal to be transmitted to the signal transmission module.

4. The signal transmission system as described in claim 3, characterized in that, It also includes a temperature detection unit connected to the DC measurement module; the temperature detection unit is located close to the signal transmission module and is used to obtain the real-time temperature of the signal transmission module. The DC measurement module is also used to compare the real-time temperature output by the temperature detection unit with the reference temperature. When the difference between the real-time detected temperature and the reference temperature exceeds a preset range, the DC measurement module automatically reacquires the compensation parameters. The reference temperature is the temperature at the time of the most recent acquisition of the compensation parameters. Alternatively, the DC measurement module is also used to output a prompt message to remind the user to reacquire the compensation parameters, and to use the temperature at the time of reacquiring the compensation parameters as the new reference temperature.

5. The signal transmission system as described in claim 4, characterized in that, The temperature detection unit includes a first temperature detection device and a second temperature detection device, which are respectively connected to the DC measurement module. The first temperature detection device is positioned close to the electro-optical conversion unit in the signal transmission module, and is used to detect the ambient temperature of the electro-optical conversion unit as a first temperature signal, and send the first temperature signal to the DC measurement module; The second temperature detection device is positioned close to the photoelectric conversion unit in the signal transmission module, and is used to detect the ambient temperature of the photoelectric conversion unit as a second temperature signal, and send the second temperature signal to the DC measurement module; The DC measurement module determines whether to reacquire compensation parameters based on the first temperature signal and the second temperature signal.

6. The signal transmission system as described in claim 1, characterized in that, It also includes a gain flattening adjustment unit, which includes a comparison unit, an adjustable resistor, and a controller. The two input terminals of the comparison unit are respectively connected to the output terminal of the signal transmission module and a reference source with preset electrical parameters. The output terminal of the comparison unit is connected to the controller and is used to compare the signal output by the signal transmission module with the reference voltage output by the reference source, and output the comparison result to the controller. The controller compares the comparison result with a pre-generated voltage difference list and generates a control signal based on the comparison result. The two ends of the adjustable resistor are respectively connected to the output terminal of the signal transmission module and the output terminal of the signal output module. Its control terminal is connected to the controller and is used to adjust the resistance value according to the control signal output by the controller, thereby adjusting the amplitude of the output signal of the signal transmission module.

7. A signal transmission method for high-voltage circuit testing, applied to the signal transmission system as described in any one of claims 1 to 6, wherein the signal transmission system comprises a signal input module, a signal transmission module, a signal output module, a bias adjustment module, and a DC measurement module; characterized in that, The signal transmission method includes a calibration phase and a measurement phase; The calibration phase includes: The signal input module receives the calibration signal and uses the calibration signal as the original transmission signal. The DC measurement module is used to detect the DC bias loss during the transmission of the original transmitted signal through the signal transmission module; The DC measurement module obtains compensation parameters based on the DC bias loss and controls the bias adjustment module to generate a DC bias compensation signal based on the compensation parameters. The measurement phase includes: The signal input module receives the test signal from an external device and uses the test signal as the original transmission signal. The bias adjustment module outputs the DC bias compensation signal; The original transmission signal is compensated using the DC bias compensation signal, and the compensated original transmission signal is output as a test acquisition signal to the signal transmission module so that the test acquisition signal output by the signal output module after electro-optical-electrical conversion and transmission is consistent with the DC bias voltage of the original transmission signal. The signal output module outputs the signal transmitted by the signal transmission module.

8. The signal transmission method as described in claim 7, characterized in that, The DC measurement module obtains compensation parameters based on the DC bias loss, and controls the bias adjustment module to generate a DC bias compensation signal based on the compensation parameters, including: The DC measurement module detects the first voltage signal at the input terminal of the signal transmission module and the second voltage signal at the output terminal of the signal transmission module; Calculate the first difference between the first voltage signal and the second voltage signal to obtain the initial compensation parameters; The initial compensation parameters are sent to the bias adjustment module for initial configuration. The bias adjustment module generates a first bias voltage based on the initial compensation parameters; The original transmitted signal is compensated using the first bias voltage; The compensated input signal is output to the signal transmission module for electro-optical-electrical transmission. The DC measurement module detects the compensated input signal and outputs the second voltage signal via the signal transmission module; Calculate the second difference between the DC bias voltage of the compensated second voltage signal and the DC bias voltage of the original transmitted signal; Determine if the second difference is equal to 0. If it is, stop executing the following steps and complete the calibration phase; otherwise, execute the following steps. The fine-tuning compensation parameters are obtained based on the second difference; The fine-tuning compensation parameters are sent to the bias adjustment module, which then superimposes the fine-tuning compensation parameters and the initial compensation parameters to generate a second bias voltage. The original transmitted signal is compensated using the second bias voltage; The compensated original transmission signal is output to the signal transmission module for electro-optical-electrical transmission.

9. The signal transmission method as described in claim 7 or 8, characterized in that, The signal transmission system further includes a temperature detection unit, and the signal transmission method further includes: The ambient temperature in the signal transmission module is monitored to obtain the real-time temperature of the signal transmission module; The DC measurement module compares the real-time temperature output by the temperature detection unit with the reference temperature, which is the temperature at the time of the most recent acquisition of compensation parameters. When the difference between the real-time detected temperature and the reference temperature exceeds the preset range, the system automatically enters the calibration phase or outputs a prompt message to remind the user to re-enter the calibration phase, so that the DC measurement module can re-acquire the compensation parameters. The temperature at which the compensation parameters are reacquired will be used as the new reference temperature. When the difference between the real-time detected temperature and the reference temperature does not exceed the preset range, the bias adjustment module maintains the second bias voltage unchanged.

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