A network analyzer based method of calibrating a splitter

Abstract

The application provides a shunt calibrating method based on a network analyzer, comprising: calibrating the network analyzer by using a calibration standard part; connecting an open circuit device and a short circuit device which are made in the same structure as the measured shunt to the network analyzer to perform in-situ compensation for shunt impedance measurement; repeatedly measuring the measured shunt at a certain frequency to obtain measurement data of the measured shunt; measuring the phase angle measurement error of the network analyzer by using a mutual inductance standard part to calibrate the phase angle measurement result of the network analyzer; and performing statistical analysis and data processing on the measurement data to obtain the calibration result of the measured shunt after data correction. The method can realize the simultaneous calibration of AC / DC difference and phase angle of the shunt in the megahertz frequency range, expand the frequency range of the shunt calibration, and help to promote the research and application of the shunt in the high-frequency current, especially the pulse current measurement field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shunt calibration, and particularly relates to a calibration method for a wideband AC / DC shunt. BACKGROUND

[0002] With the development and progress of science and technology, high-frequency current (including periodic continuous current and transient pulse current) has been widely applied in many fields such as production and life, power grid monitoring, scientific research and national defense industry, and the importance of accurate measurement of high-frequency current is self-evident. Shunts are widely used in high-frequency current measurement field due to the advantages of simplicity, accuracy, reliability, high linearity and wide frequency band, and high-precision shunts are often used as reference standards for calibration of other current measuring instruments. When used for high-precision current measurement, calibration of shunts is very necessary, especially for high-frequency applications.

[0003] The impedance of the shunt varies with the frequency, which is mainly characterized by AC / DC difference and phase angle. The AC / DC difference is defined as the change of the amplitude of the shunt impedance relative to its DC resistance value, and is usually expressed in μΩ / Ω (or ppm); the phase angle is determined by the real part and the imaginary part of the shunt impedance, and is usually expressed in μrad. At present, the calibration of high-grade shunts usually adopts the thermoelectric conversion method and the direct comparison method. The thermoelectric conversion method uses a standard thermoelectric converter, and uses the fixed AC power and the adjustable standard DC power applied before and after to measure the output voltage of the thermocouple fixed on the converter, and when the output voltages are equal, the effective value of the applied AC power is equal to the DC power. This method can only calibrate the AC / DC difference of the shunt. The direct comparison method is the most common calibration method, and when calibrating the shunt, a phase comparator is used to compare the output voltages of the standard shunt and the shunt to be calibrated in series to obtain the phase difference of the two shunts. This method is usually used to calibrate the phase angle of the shunt. The special design of the measurement system based on the direct comparison method can also be used to calibrate the AC / DC difference and the phase angle of the shunt.

[0004] In view of the calibration methods used for high-grade shunts, the thermoelectric conversion method can only calibrate the AC / DC difference of the shunt, and the direct comparison method can be used to calibrate the AC / DC difference or the phase angle of the shunt, and is mainly used to calibrate the phase angle. When the above-mentioned methods are used to calibrate the shunt with a nominal current, the frequency range of the thermoelectric conversion method for calibrating the AC / DC difference is only up to 100 kHz, and the frequency range of the direct comparison method for calibrating the phase angle is only up to 200 kHz, which is far lower than the calibration requirement of the current measurement frequency range up to megahertz. Therefore, it is urgent to design a method for simultaneously calibrating the AC / DC difference and the phase angle of the shunt in a higher hertz frequency range (such as 30 MHz), so as to promote the research and application of the shunt in the field of high-frequency current, especially pulse current measurement. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a shunt calibrating method based on a network analyzer, which can realize synchronous calibration of AC-DC difference and phase angle of the shunt in a megahertz frequency range and ensure high calibration accuracy.

[0006] The present application is implemented as follows: a shunt calibrating method based on a network analyzer, comprising the following steps:

[0007] In step S10, a calibration standard is used to calibrate the network analyzer in correspondence with the measurement method and range.

[0008] In step S20, an open-circuit device and a short-circuit device with the same structure as the measured shunt are used to compensate for the impedance measurement of the shunt in situ.

[0009] In step S30, the network analyzer is used to measure the shunt impedance parameters of the measured shunt, and the measurement results of the AC-DC difference and phase angle of the shunt are obtained.

[0010] In step S40, the phase angle measurement error of the network analyzer is measured by using a mutual inductance standard, and the phase angle measurement results of the network analyzer are calibrated.

[0011] In step S50, the measurement results of the AC-DC difference and the phase angle calibration results are statistically analyzed and data processed to obtain the calibration results of the measured shunt data after correction.

[0012] Further, the calibration standard is a calibration standard provided by the network analyzer or a calibration standard defined by the user, which is used to eliminate the system error of the network analyzer.

[0013] Further, the mutual inductance standard is a group of air medium mutual inductance or a group of PCB medium mutual inductance.

[0014] Further, the open-circuit device and the short-circuit device with the same structure as the shunt are designed through simulation analysis.

[0015] Further, the shunt impedance parameters include DC resistance value, AC impedance and phase angle.

[0016] Further, step S30 comprises: according to the frequency range applied by the measured shunt and the technical index of the network analyzer used, the gain phase port of the network analyzer is used for measurement when the lower frequency band is concerned, and the S parameter port of the network analyzer is used for measurement when the higher frequency band is concerned.

[0017] Further, the measurement of the shunt impedance parameters in step S30 is repeated at a certain frequency, and the specific process is as follows:

[0018] The impedance parameters of the shunt under test are repeatedly measured continuously within a day, and repeatedly measured at weekly or longer intervals.

[0019] Further, the step S50 further comprises:

[0020] Step S51, applying a data fitting method to statistically analyze the measurement data to obtain the frequency-AC / DC difference curve and the frequency-phase angle curve under the corresponding frequency band;

[0021] Step S52, according to the measurement results obtained by using the gain phase method or the S parameter method, the unmeasured frequency band is extended to obtain the corresponding expected results of the unmeasured frequency band.

[0022] Further, the method further comprises step S60, when the shunt is used, according to the different accuracy needs of the application scene, the frequency-AC / DC difference curve and the frequency-phase angle curve of the shunt are error corrected to obtain the calibration results of the frequency-AC / DC difference curve and the frequency-phase angle curve under different applications.

[0023] Further, the method further comprises, the data obtained by fitting are simultaneously analyzed by using the gain phase method and the S parameter method, and the calibration results of the shunt under test are evaluated, specifically: the frequency upward extension analysis of the measurement results is performed by using the gain phase method, and the frequency downward extension analysis of the measurement results is performed by using the S parameter method, and the reliability of the calibration results is further evaluated according to the consistency degree of the two extension analyses.

[0024] The advantages of the present application are:

[0025] 1. The AC / DC difference and phase angle calibration of the shunt can be completed at the same time.

[0026] 2. The frequency range of the shunt calibration is significantly expanded to high frequency, which can promote the research and application implementation of the high frequency current measurement value traceability of the shunt.

[0027] 3. The calibration accuracy and reliability are improved by comparing and verifying the two calibration methods of the gain phase method and the S parameter method.

[0028] 4. The simulation analysis data of the mutual inductance standard part and the shunt on-off circuit can provide an effective basis for evaluating the calibration results of the shunt. BRIEF DESCRIPTION OF DRAWINGS

[0029] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0030] Figure 1 is a flowchart of a shunt calibration method based on a network analyzer.

[0031] Figure 2is the schematic diagram of the working principle of the calibration shunt of the network analyzer of the present application.

[0032] Figure 3 is the flowchart of statistical analysis and data processing of the calibration results in the present application.

[0033] Figure 4 is the schematic diagram of the network analyzer and the circuit structure of the present application.

[0034] Figure 5 is the schematic diagram of the equivalent circuit model of the shunt in an embodiment of the present application. DETAILED DESCRIPTION

[0035] Please refer to Figures 1 to 5 The shunt calibration method based on the network analyzer of the present application comprises the following steps:

[0036] Step S10, using the calibration standard to calibrate the network analyzer which is fully preheated in the corresponding measurement method and measurement range;

[0037] Step S20, using the open circuit and short circuit which are made of the same structure as the measured shunt to compensate for the in-situ shunt impedance measurement; this step can compensate for the parameters such as the lead part and the geometric structure of the shunt itself in the application, thereby improving the measurement accuracy;

[0038] Step S30, using the network analyzer to measure the shunt impedance parameters of the measured shunt, and obtaining the measurement results of the AC-DC difference and the phase angle of the shunt;

[0039] Step S40, using the mutual inductance standard to measure the phase angle measurement error of the network analyzer, and calibrating the phase angle measurement results of the network analyzer;

[0040] Step S50, statistically analyzing and data processing the measurement results of the AC-DC difference and the phase angle calibration results of the shunt to obtain the calibration results of the measured shunt data after correction.

[0041] Preferably, the calibration standard is a calibration standard provided by the network analyzer or a calibration standard defined by the user, which is used to eliminate the system error of the network analyzer.

[0042] Preferably, the mutual inductance standard is a group of air medium mutual inductance or a group of PCB medium mutual inductance, and the mutual inductance standard is designed for calibrating the phase angle measurement error of the network analyzer.

[0043] Preferably, the open circuit and the short circuit which are designed through simulation analysis are of the same structure as the shunt.

[0044] Preferably, the shunt impedance parameters include DC resistance value, AC impedance and phase angle.

[0045] Preferably, the step S30 comprises: according to the frequency range applied by the measured shunt and the network analyzer technology index used, the gain phase port of the network analyzer is used for measurement when the concerned frequency band is low, and the S parameter port of the network analyzer is used for measurement when the concerned frequency band is high. Specifically, when the frequency to be measured falls within the frequency range of 1 kHz-10 MHz, the gain phase port of the network analyzer is used for shunt impedance parameter measurement, and when the frequency to be measured falls within the frequency range of 10 MHz-30 MHz, the S parameter port of the network analyzer is used for shunt impedance parameter measurement.

[0046] Preferably, the measurement of the shunt impedance parameter in the step S30 is repeated at a certain frequency, so as to ensure the short-term repeatability and long-term stability of the measurement results, and the specific implementation is as follows:

[0047] The impedance parameter of the measured shunt is repeatedly measured continuously within one day, and repeatedly measured at a weekly or longer interval.

[0048] Preferably, the step S50 further comprises:

[0049] Step S51, applying a data fitting method to statistically analyze the measurement data to obtain the frequency-AC / DC difference curve and the frequency-phase angle curve under the corresponding frequency band;

[0050] Step S52, extending the unmeasured frequency band according to the measurement results obtained by using the gain phase method or the S parameter method to obtain the corresponding expected results of the unmeasured frequency band. Since the measured frequency band is measured according to the need, only a part of the frequency band may be measured in actual measurement. If the unmeasured frequency band needs to be used, it can be obtained by extension, for example, we have only measured the data within 30 MHz, and if higher frequency data is needed, the S parameter method can be selected to extend the measurement results to obtain the frequency-AC / DC difference curve and the frequency-phase angle curve of the required frequency band.

[0051] Preferably, the method further comprises a step S60, according to the different accuracy needs of the application scene, the frequency-AC / DC difference curve and the frequency-phase angle curve of the shunt are error-corrected to obtain the calibration results of the frequency-AC / DC difference curve and the frequency-phase angle curve under different applications.

[0052] Preferably, the method further comprises, simultaneously using the gain-phase method and the S-parameter method to comprehensively analyze the fitted data, and evaluating the calibration result of the measured shunt, specifically: using the gain-phase method to analyze the upward frequency extension of the measurement result, and using the S-parameter method to analyze the downward frequency extension of the measurement result, and further evaluating the reliability of the calibration result according to the consistency of the two extension analyses.

[0053] In a specific embodiment, a typical vector network analyzer is used, as shown in the figure, which includes a vector network analyzer and its circuit structure diagram, and can provide common network measurement and analysis functions in a frequency range of several GHz, and the network analyzer integrated with impedance analysis functions can more conveniently perform impedance measurement and analysis of the measured device. Figure 4 In the final data comprehensive analysis and evaluation stage, in order to further improve the calibration result accuracy of the high-level shunt, we can increase the consideration of the shunt frequency response change caused by parasitic inductance and stray capacitance, as shown in Figure 5 The equivalent circuit model for high-frequency application of the shunt for high-level application is shown in the figure, which is a two-port device, the left end represents the current input and output port of the shunt, and the right end represents the voltage measurement port of the shunt, and the parasitic inductance and stray capacitance in the figure are the main factors causing the shunt frequency response change, so in the final evaluation, we also correct the shunt lead error according to the electromagnetic simulation result, reduce and eliminate these parasitic inductance and stray capacitance influencing factors, and improve the calibration result of the high-level shunt. The shunt calibration method involved in the present application is also based on the above-mentioned vector network analyzer.

[0054] Compared with the current main shunt calibration method, the calibration method involved in the present application has the following advantages:

[0055] The shunt is calibrated by using the vector network analyzer, and the AC-DC difference and phase angle of the shunt can be calibrated at the same time; the calibration method of the present application includes the calibration of the network analyzer itself, the shunt calibration measurement by the network analyzer gain-phase method and S-parameter method, and the analysis and correction of the influence of the shunt model distribution parameters on the measurement result. The correction of the phase angle measurement of the network analyzer is performed by using a specially designed mutual inductance standard, and the influence introduced by the shunt lead parameters is compensated and corrected by using a short-circuit device and an open-circuit device specially designed to be exactly the same as the measured shunt, thereby improving the overall calibration accuracy; the data fitting algorithm is used to improve the calibration accuracy of the shunt, and the frequency extension calibration range is extended by using the gain-phase method and the S-parameter method, so that the frequency range of the shunt calibration is significantly expanded to high frequency, and the research and application implementation of the high-frequency current measurement value traceability of the shunt are promoted; the present application also designs a comparison and analysis by using the gain-phase method and the S-parameter method for two calibration methods, verifies and analyzes the calibration result, and improves the accuracy and reliability of the calibration.

[0056] While the foregoing describes specific embodiments of the application, one of ordinary skill in the art will further appreciate that the specific exemplary embodiments described are meant to be illustrative only and are not intended to limit the scope of the application. Changes, modifications, and equivalents which would occur to one skilled in the art upon a reading of the foregoing description are meant to be encompassed within the scope of the application.

Claims

1. A network analyzer based method of calibrating a splitter, characterized by: The method comprises the following steps: Step S10, calibrating the network analyzer with a calibration standard piece corresponding to the measurement method and the measurement range; Step S20, using the open circuit and the short circuit made of the same structure as the shunt to be measured to compensate for the impedance measurement of the shunt in situ; Step S30, measuring the shunt impedance parameters of the shunt to be measured by using the network analyzer to obtain the measurement results of the AC-DC difference and the phase angle of the shunt; specifically, when the frequency to be measured falls within the frequency range of 1 kHz to 10 MHz, the gain phase port of the network analyzer is used to measure the shunt impedance parameters, and when the frequency to be measured falls within the frequency range of 10 MHz to 30 MHz, the S parameter port of the network analyzer is used to measure the shunt impedance parameters; Step S40, measuring the phase angle measurement error of the network analyzer by using a mutual inductance standard piece to calibrate the phase angle measurement result of the network analyzer; Step S50, statistically analyzing and processing the measurement results of the AC-DC difference and the phase angle of the shunt to obtain the calibration results of the shunt to be measured after data correction; The step S50 further comprises: Step S51, applying a data fitting method to statistically analyze the measurement data to obtain the frequency-AC-DC difference curve and the frequency-phase angle curve under the corresponding frequency band; Step S52, extending the unmeasured frequency band according to the measurement results obtained by using the gain phase method or the S parameter method to obtain the corresponding expected results of the unmeasured frequency band; The method further comprises comprehensively analyzing the fitted data by using the gain phase method and the S parameter method to evaluate the calibration results of the shunt to be measured, specifically, the frequency of the measurement result is extended upwards by using the gain phase method, the frequency of the measurement result is extended downwards by using the S parameter method, and the reliability of the calibration results is further evaluated according to the consistency of the two extension analyses.

2. The network analyzer based directional coupler calibration method of claim 1, wherein: The calibration standard piece is a calibration standard piece provided by the network analyzer or a calibration standard piece defined by the user, which is used to eliminate the system error of the network analyzer.

3. The network analyzer based directional coupler calibration method of claim 1, wherein: The mutual inductance standard piece is a group of air medium mutual inductance or a group of PCB medium mutual inductance.

4. The network analyzer based directional coupler calibration method of claim 1, wherein: The open circuit and the short circuit are designed by simulation analysis and have the same structure as the shunt.

5. The network analyzer based directional coupler calibration method of claim 1, wherein: The shunt impedance parameters include the DC resistance value, the AC impedance and the phase angle.

6. The network analyzer based directional coupler calibration method of claim 1, wherein: The step S30 comprises: according to the frequency range applied by the shunt to be measured and the technical index of the network analyzer used, the gain phase port of the network analyzer is used for measurement when the frequency band concerned is low, and the S parameter port of the network analyzer is used for measurement when the frequency band concerned is high.

7. A network analyzer based method of calibrating a splitter as recited in claim 1, wherein: The measurement of the shunt impedance parameters in step S30 is repeated measurement at a certain frequency, specifically as follows: The impedance parameters of the shunt to be measured are repeatedly measured continuously within one day and repeatedly measured at every week or longer interval.

8. The network analyzer based directional coupler calibration method of claim 1, wherein: The method further comprises step S60, according to the different accuracy requirements of the application scene, the frequency-AC-DC difference curve and the frequency-phase angle curve of the shunt are error corrected to obtain the calibration results of the frequency-AC-DC difference curve and the frequency-phase angle curve under different applications.

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