A method for obtaining the transmission coefficient of electromagnetic pulse measurement system

Abstract

The present invention solves the problem that existing methods for obtaining transmission coefficients through time-domain standard square wave calibration do not fully utilize prior information about the signal to be measured, and measurement accuracy can be further improved. This invention provides a method for calculating the transmission coefficient based on the calibration results of the measurement system's frequency-domain response and a library of waveforms to be measured. The method comprises the following steps: Step 1: Obtaining the frequency response of the electromagnetic pulse measurement system, constructing a library of waveforms to be measured A, and obtaining the value of each waveform feature point in the library A; Step 2: Calculating the output waveform of each waveform after passing through the electromagnetic pulse measurement system and obtaining the value of the output waveform feature point; Step 3: Based on the value of each waveform feature point in Step 1 and the value of the output waveform feature point of the corresponding waveform after passing through the electromagnetic pulse measurement system in Step 2, calculating the transmission coefficient k of the electromagnetic pulse measurement system. The method proposed by the present invention improves the measurement accuracy of the transmission coefficient method and is highly practical.

Description

Technical Field

[0001] The present invention relates to a method for obtaining a transmission coefficient of an electromagnetic pulse measurement system, and in particular to a method for obtaining the transmission coefficient of an electromagnetic pulse measurement system by calculation based on prior knowledge of a waveform to be measured and a frequency response of a measurement system. Background Art

[0002] There are two methods to estimate the measured signal based on the output of the electromagnetic pulse measurement system: one is to combine the frequency response of the measurement system and restore the measured signal through a series of filtering, Fourier transform, compensation and other methods. However, the back-end processing of this method is highly targeted and has high requirements for users; the other is the transmission coefficient method. The principle of this method is: when the bandwidth of the electromagnetic pulse measurement system is wide enough relative to the measured signal, the output and input of the electromagnetic pulse measurement system can be considered to have the same waveform, differing only in amplitude. The transmission coefficient is defined as the ratio of the amplitude of the standard input pulse waveform to the amplitude of the output waveform, which is obtained by square wave calibration in the time domain. Then, the transmission coefficient is multiplied by the response of the electromagnetic pulse measurement system to obtain the measured value of the signal to be measured. This method is simple and easy to operate and is widely used in engineering.

[0003] However, the bandwidth of general electromagnetic pulse measurement systems is limited, and there is a certain degree of jitter in the frequency response within the operating frequency band. In existing methods, the method of using square waves to calibrate the transmission coefficient in the time domain does not consider the spectral characteristics of the waveform to be measured, and the measured transmission coefficient has relatively low accuracy. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that the existing method of obtaining the transmission coefficient through time domain standard square wave calibration does not fully utilize the prior information of the signal to be measured and the accuracy of the measured transmission coefficient is relatively low, and provide a method for obtaining the transmission coefficient of the electromagnetic pulse measurement system.

[0005] The design idea of the present invention is:

[0006] Based on the prior information of the signal to be measured and the frequency response of the measurement system, the measurement process is mathematically simulated to obtain the output of the signal to be measured after passing through the measurement system. The transmission coefficient that takes into account the prior knowledge of the signal to be measured is calculated through a mathematical formula.

[0007] In order to achieve the above ideas, the technical solutions of the present invention are as follows:

[0008] A method for obtaining a transmission coefficient of an electromagnetic pulse measurement system comprises the following steps:

[0009] Step 1: Obtain the frequency response H(jω) of the electromagnetic pulse measurement system, construct a waveform library A to be measured based on prior information of the waveform to be measured, and obtain the value of each waveform feature point in the waveform library A to be measured, wherein the waveform library A to be measured includes L waveforms;

[0010] Step 2: Based on H(jω) in step 1 and the L waveforms in the waveform library A to be measured, calculate the output waveform of each waveform after passing through the electromagnetic pulse measurement system, and obtain the value of the output waveform feature point;

[0011] Step 3: Based on the value of each waveform characteristic point in the waveform library A to be measured in step 1 and the value of the waveform characteristic point output by the corresponding waveform after passing through the electromagnetic pulse measurement system in step 2, the transmission coefficient k of the electromagnetic pulse measurement system is calculated using the following formula;

[0012]

[0013] Among them, x i,c Indicates the value of the i-th waveform feature point in the waveform library A to be tested, u i,c It represents the value of the characteristic point of the output waveform of the i-th waveform in the waveform library A to be measured after passing through the electromagnetic pulse measurement system.

[0014] Furthermore, in step 1, the frequency response H(jω) of the electromagnetic pulse measurement system is obtained through the product manual or calibration results.

[0015] Furthermore, in step 2, the output waveform of each waveform after passing through the electromagnetic pulse measurement system is calculated using the following formula:

[0016]

[0017] Among them, x i Indicates the i-th waveform in the waveform library A to be tested, and Represents Fourier transform and inverse Fourier transform, u i It represents the output waveform of the i-th waveform in the waveform library A to be measured after passing through the electromagnetic pulse measurement system, j is an imaginary number, and ω is the angular frequency.

[0018] Furthermore, in step 1, the waveform to be measured is a double exponential waveform;

[0019] The prior information includes the range of the leading edge tr and the range of the half-width tw of the double exponential waveform.

[0020] Furthermore, in step 1, the method for constructing the waveform library A to be measured based on the prior information of the waveform to be measured is as follows:

[0021] Set the leading edge step length to U and the half-width step length to P, then within the leading edge tr range [Q, W] and the half-width tw range [R, F], L = ((WQ) / U+1)((FR) / P+1) waveforms to be tested can be formed.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The present invention provides a method for calculating the transmission coefficient based on the frequency response calibration results of the electromagnetic pulse measurement system and the waveform library to be measured, which fully utilizes the prior knowledge of the signal to be measured and the frequency response of the measurement system, and improves the measurement accuracy of the transmission coefficient method.

[0024] 2. The transmission coefficient calculated by the present invention can be directly used to estimate the characteristic value of the signal to be measured, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the process of an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The present invention proposes a method for obtaining the transmission coefficient of an electromagnetic pulse measurement system, such as Figure 1 As shown, the specific steps include:

[0028] Step 1: Obtain the frequency response H(jω) of the electromagnetic pulse measurement system, and construct a waveform library A to be measured based on prior information of the waveform to be measured, and obtain the value of each waveform feature point in the waveform library A to be measured, wherein the waveform library A to be measured includes L waveforms. The feature point can be a peak value, a flat-top peak value, etc. of the waveform to be measured according to actual needs. In this example, the waveform to be measured is a bi-exponential waveform. The prior information includes the range of the leading edge tr and the range of the half-width tw of the bi-exponential waveform. The leading edge range and half-width range of the bi-exponential waveform are obtained through expert experience or simulation calculations, and the peak value of the bi-exponential waveform is selected as the value of the feature point;

[0029] A. Obtain the frequency response H(jω) of the electromagnetic pulse measurement system, where j is an imaginary number and ω represents the angular frequency;

[0030] Taking an electromagnetic pulse measurement system as an example, it is necessary to ensure that the bandwidth, size, available front edge, measurement range, waveform fidelity, etc. of the selected electromagnetic pulse measurement system meet the test requirements;

[0031] In this example, it is assumed that the electromagnetic pulse current measurement system has the same frequency response as a first-order low-pass Butterworth filter, and the 3dB bandwidth is 70MHz;

[0032] Specifically, the frequency response H(jω) of the electromagnetic pulse current measurement system can also be obtained through the product manual or calibration results;

[0033] B. Construct a waveform library A based on the prior information of the waveform to be measured, and obtain the value of each waveform feature point in the waveform library A as follows:

[0034] Given a bi-exponential waveform, let the ranges of tr and tw be [5 ns, 10 ns] and [60 ns, 100 ns], with step sizes of 0.5 ns and 1 ns, respectively. tr represents the leading edge from 10% to 90% of the peak value of the bi-exponential waveform, and tw represents the half-width from 50% to 50% of the peak value of the bi-exponential waveform. Random combinations of the leading edge tr and half-width tw can form 451 waveforms. These 451 waveforms constitute the waveform library A to be tested, i.e., L = 451.

[0035] According to each waveform, obtain the peak value of each waveform. The peak value is the value of the characteristic point. In this example, the peak value of all waveforms is set to 1.

[0036] Step 2: If Figure 1 As shown, according to H(jω), the output waveform of each waveform in the waveform library A to be measured after passing through the electromagnetic pulse measurement system is calculated, and the value of the characteristic point of the output waveform is obtained;

[0037] In step 2, the selection of the characteristic points of the output waveform is the same as that of the waveform in step 1, both of which are peaks;

[0038] Specific:

[0039] The output waveform of each waveform after passing through the electromagnetic pulse measurement system is calculated using the following formula:

[0040]

[0041] Among them, x i Indicates the i-th waveform in the waveform library A to be tested, and Respectively represent Fourier transform and inverse Fourier transform; u i It represents the output waveform of the i-th waveform in the waveform library A after passing through the electromagnetic pulse measurement system, j is an imaginary number, and ω is the angular frequency;

[0042] As shown in Table 1, several groups of output waveform peak values are given:

[0043] Table 1

[0044]

[0045] Step 3: Based on the values of the characteristic points of each waveform output after passing through the electromagnetic pulse measurement system, and the values of the characteristic points of each waveform in step 1, the transmission coefficient k of the electromagnetic pulse measurement system is calculated using the following formula;

[0046]

[0047] Among them, x i,c Indicates the value of the characteristic point of the i-th waveform in the waveform library A to be tested, u i,c Represents the value of the characteristic point of the output waveform corresponding to the i-th waveform in the waveform library A to be tested;

[0048] In this embodiment, x i,c =1,i=1,2L, , we calculated k = 1.012.

[0049] In order to verify the correctness of this scheme, the electromagnetic pulse measurement system was calibrated using square waves, and k = 1.0 was obtained;

[0050] The error when measuring the waveform in the waveform library A using this measurement system is calculated using the following formula:

[0051]

[0052] Among them, abs means taking the absolute value;

[0053] The error of the present invention is 0.73%, while the error of the system calibration using square waves is 1.91%, which proves that the method provided by the present invention improves the measurement accuracy of the transmission coefficient method.

Claims

1. A method for obtaining the transmission coefficient of an electromagnetic pulse measurement system, characterized in that: The following steps are involved: Step 1: Obtain the frequency response H(jω) of the electromagnetic pulse measurement system, construct a waveform library A to be measured based on prior information of the waveform to be measured, and obtain the value of each waveform feature point in the waveform library A to be measured, wherein the waveform library A to be measured includes L waveforms; Step 2: Based on H(jω) in step 1 and the L waveforms in the waveform library A to be measured, calculate the output waveform of each waveform after passing through the electromagnetic pulse measurement system, and obtain the value of the output waveform feature point; Step 3: Based on the value of each waveform characteristic point in the waveform library A to be measured in step 1 and the value of the waveform characteristic point output by the corresponding waveform after passing through the electromagnetic pulse measurement system in step 2, the transmission coefficient k of the electromagnetic pulse measurement system is calculated using the following formula; Among them, x i,c Indicates the value of the i-th waveform feature point in the waveform library A to be tested, u i,c Represents the value of the output waveform feature point of the i-th waveform in the waveform library A to be measured after passing through the electromagnetic pulse measurement system; In step 2, the output waveform of each waveform after passing through the electromagnetic pulse measurement system is calculated using the following formula: Among them, x i Indicates the i-th waveform in the waveform library A to be tested, and Represents Fourier transform and inverse Fourier transform, u i It represents the output waveform of the i-th waveform in the waveform library A to be measured after passing through the electromagnetic pulse measurement system, j is an imaginary number, and ω is the angular frequency.

2. The method for obtaining the transmission coefficient of an electromagnetic pulse measurement system according to claim 1, characterized in that: In step 1, the frequency response H(jω) of the electromagnetic pulse measurement system is obtained through the product manual or calibration results.

3. A method for obtaining a transmission coefficient of an electromagnetic pulse measurement system according to any one of claims 1 to 2, characterized in that: In step 1, the waveform to be measured is a double exponential waveform; The prior information includes the range of the leading edge tr and the range of the half-width tw of the double exponential waveform.

4. The method for obtaining the transmission coefficient of an electromagnetic pulse measurement system according to claim 3, characterized in that: In step 1, the method for constructing the waveform library A to be measured based on the prior information of the waveform to be measured is as follows: Set the leading edge step length to U and the half-width step length to P, then within the leading edge tr range [Q, W] and the half-width tw range [R, F], L = ((WQ) / U+1)((FR) / P+1) waveforms to be tested can be formed.

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