A correction method for electromagnetic environment simulation based on PCHIP

Abstract

The present invention provides a correction method for electromagnetic environment simulation based on PCHIP. First, sample points are selected within the frequency band of the simulated electromagnetic environment as the power comparison points between the theoretical model and the actual measurement. The calculation result of the theoretical model is corrected according to the actual measurement result. Then, the piecewise cubic Hermite interpolation method is used to interpolate and fit the power results at other frequency points based on the corrected theoretical model. By randomly sampling verification points in the frequency band of the simulated electromagnetic environment, it is checked whether the calculation result of the theoretical model at the verification points meets the confidence level. Through continuous iterative correction, the calculation result of the theoretical model and the actual measurement result meet the confidence level requirements at the verification points. The present invention reduces the test amount required to correct the simulation model in actual engineering, establishes an electromagnetic environment simulation model that takes into account both accuracy and efficiency, avoids a large number of experiments for verifying the model, simplifies the calculation process, and reduces the actual calculation amount.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic environment simulation, and in particular to a correction method for electromagnetic environment simulation. Background Art

[0002] In modern warfare, with the extensive use of electronic information equipment, the battlefield electromagnetic environment has become increasingly complex. Whether the frequency-using equipment can operate normally in the complex electromagnetic environment has become an important factor affecting the battlefield situation. Therefore, it is of great significance to explore the electromagnetic environment effect problem of frequency-using equipment. Due to the numerous uncertain factors, complex environment, and high experimental costs in the real experimental environment, it is difficult to deeply understand the electromagnetic environment effect of frequency-using equipment. Therefore, it is necessary to simulate the electromagnetic environment. During the simulation process, when the frequency points are the same, there is an error between the theoretically calculated power and the measured power, and the error changes with the frequency. When it is necessary to simulate an electromagnetic environment with a large frequency band and power range, it is time-consuming and laborious to correct the error of the model through actual measurement methods. Therefore, an electromagnetic environment simulation correction method that takes into account both accuracy and efficiency is of great significance for the research and evaluation of the effects of frequency-using equipment. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a correction method for electromagnetic environment simulation based on PCHIP. The present invention provides an electromagnetic environment simulation correction method that combines a theoretical model and measured data. First, determine the confidence levels of the theoretical results and the measured results. Then, select sample points within the frequency band of the simulated electromagnetic environment and use them as the power comparison points between the theoretical model and the actual measurement. Correct the calculation results of the theoretical model according to the measured results. Then, use the piecewise cubic Hermite interpolation method to interpolate and fit the power results at other frequency points based on the corrected theoretical model. Finally, select verification points in the frequency band of the simulated electromagnetic environment according to the random sampling principle to check whether the calculation results of the theoretical model at the verification points meet the confidence levels. If the confidence level requirements are not met, continue to select sample points within the frequency band to enrich the sample size, and repeat the correction and interpolation fitting steps. By continuously iteratively correcting the theoretical model, the calculation results of the theoretical model and the measured results meet the confidence level requirements at the verification points. Thereby, it is possible to avoid performing a large number of actual measurements to correct the theoretical model, thereby improving the efficiency of electromagnetic environment simulation and ensuring the accuracy requirements.

[0004] The technical solution adopted by the present invention to solve its technical problems includes the following steps:

[0005] Step 1: Model the electromagnetic environment;

[0006] The simulation of the electromagnetic environment includes injection simulation and anechoic chamber radiation simulation. Theoretical models are established separately for different environmental simulation methods; the parameters of the simulated electromagnetic environment are set according to the actual electromagnetic environment under study, or according to the object to be modeled; the modeling process is as follows: first, determine the simulation model parameters of the electromagnetic environment, including the signal regime, signal frequency band, and signal power. Then, establish a theoretical simulation model of the electromagnetic environment according to the corresponding signal regime; after establishing the theoretical simulation model of the electromagnetic environment, determine the sample size according to the principle of random sampling and extract sample points within the frequency band range. Calculate the in-band average power value of the received signal at the sample points through the simulation model;

[0007] Step 2: Actual measurement

[0008] Measure the power value of the received signal at the sample frequency points in actual measurement, analyze the mathematical relationship between the frequency and the measured power, and thus correct the simulation model of the electromagnetic environment;

[0009] Step 3: Fit the simulation results based on the measured results and the PCHIP method;

[0010] According to the measured data obtained from the injection measurement and radiation measurement in Step 2, obtain the in-band average power values of the received signals at n sample frequency points [P 1 , P 2 , … P n . According to the actually measured data, correct the theoretical in-band average power values of the received signals at the sample frequency points in the simulation model [P` 1 , P` 2 , … P` n so that the calculated power value at the sample points is equal to the measured power value, that is, P i = P` i , i = 1, 2, … n;

[0011] Using the PCHIP method and combining the mathematical relationship between the measured power and the frequency obtained from the analysis in Step 2, interpolate and fit the discrete power values [P` 1 , P` 2 , … P` n of the injection simulation electromagnetic environment simulation model and the radiation simulation electromagnetic environment simulation model, so as to obtain the in-band average power values of the received signals outside the sample frequency points within the simulation frequency band and power range;

[0012] Step 4: Confidence level test

[0013] Randomly select verification points within the frequency band and power range determined in Step 2. The absolute error between the signal reception power of the corrected simulation model at the verification points and the actually measured signal reception power should be within the confidence range. The value range of the confidence is α ∈ [-0.5dB, 0.5dB]. When P 模型 and P 实测 's power difference is within the confidence, it can be considered that the calculated power P 模型 of the model correction and the measured power P 实测 meet the confidence requirements; if the absolute error between the signal reception power calculated by the theoretical model and the actually measured received signal power is greater than 0.5dB, that is, the absolute error is outside the confidence value range, then the verification point is supplemented to the measured samples as a sample point, and then repeat Steps 1 to 3 until the verification points randomly sampled by the theoretical model meet the confidence requirements, then the correction of the final theoretical model is completed.

[0014] In the said Step 1, an AM system signal electromagnetic environment is adopted, then:

[0015] (1) Electromagnetic environment injection simulation;

[0016] First, determine the simulation model parameters of the model according to the modeling object, and then establish a mathematical model of the electromagnetic environment corresponding to the signal system;

[0017] The expression form of the AM signal is:

[0018] S AM (t) = [A 0 + m(t)]cos(2πf c t + φ) (2)

[0019] Among them, A 0 is the DC level, m(t) is the baseband signal, that is, the original electrical signal, fc is the carrier frequency, is the initial phase;

[0020] The value range of m(t) is [-A m , +A m , then the modulation index of AM is:

[0021]

[0022] For the AM signal, the bandwidth calculation formula is:

[0023] B = 2R s (4)

[0024] Among them, B is the bandwidth, R s is the baseband signal rate;

[0025] Mathematically model the AM signal. Within the frequency band of the determined model of the AM signal, select sample points at an interval of f 1 Hz, keep other parameters unchanged, and calculate the signal power of the transmission power. The average power P rec within the signal band is equal to the transmission power P tran minus the system loss P loss , that is:

[0026] P rec = P tran - P loss (5)

[0027] In the formula, P rec is the received signal power, P tran is the transmitted signal power, and P loss is the system loss;

[0028] (2) Radiative simulation in an anechoic chamber for electromagnetic environment;

[0029] Keep the modulation index and baseband signal rate unchanged. Within the frequency band of the determined model of the AM signal, select sample points at an interval of f 2 Hz, calculate the signal power of the transmission power. The average power within the signal band during radiative simulation is equal to the transmission power minus the system loss minus the path loss, that is:

[0030] P rec = P tran - P loss - P path (6)

[0031] Among them, P rec is the received signal power, P tran is the transmitted signal power, P loss is the system loss, and P path is the path loss.

[0032] In the second step mentioned above, the measurement steps are:

[0033] (1) Injection measurement

[0034] During the actual measurement of injection electromagnetic environment simulation, use an instrument to generate a modulation signal, set the instrument parameters to make the instrument generate a signal that is exactly the same as the signal system, frequency, transmission power, and baseband signal rate in the injection simulation in the first step. Use a spectrum analyzer to observe the frequency domain characteristics of the signal and compare them with the theoretical simulation frequency domain characteristics;

[0035] Within the frequency band of the determined model of the AM signal, change the RF frequency at an interval of f 1 Hz, keep other parameters unchanged, measure the power, and obtain the average power within the received signal band at the sample frequency points;

[0036] Set the output power range of the signal source, change the output power of the signal source at intervals of 1 dBm, keep other parameters unchanged, measure the average in-band power using a spectrum analyzer, and obtain the output power of the signal source and the actually measured power of the spectrum analyzer;

[0037] (2) Radiative measurement

[0038] During the actual measurement of the radiative electromagnetic environment simulation, use an instrument to generate a modulation signal, set parameters such as the signal modulation method, frequency, and power to be consistent with the theoretical simulation, use a spectrum analyzer to observe the frequency-domain characteristics of the signal, and compare them with the frequency-domain characteristics of the theoretical simulation;

[0039] Within the frequency band of the AM signal determination model, change the radio frequency at intervals of f 2 Hz, keep other parameters unchanged, measure the power, and obtain the output power at different frequencies under experimental conditions.

[0040] Change the output power of the signal source, change the output power of the signal source at intervals of 1 dBm, keep other parameters unchanged, record the average in-band power of the spectrum analyzer, and obtain the relationship between the signal source output and the spectrum analyzer input.

[0041] The specific steps of PCHIP interpolation in step three are as follows:

[0042] The piecewise cubic Hermite interpolation (PCHIP) method not only satisfies the equality of function values at the nodes but also satisfies the equality of first derivative values at the nodes. Therefore, the fitted curve will be smoother and the accuracy will be higher.

[0043] Arrange the actually measured sample points in ascending order of frequency, denoted as [x 0 , x 1 , x 2 , …, x n , and the actually measured power at the corresponding frequency points is denoted as [y 0 , y 1 , y 2 , …, y n , where x 0 ≤ x 1 ≤ … ≤ x n ;

[0044] Based on the idea of piecewise interpolation, by continuously performing piecewise cubic Hermite interpolation (PCHIP) between adjacent two sample points, finally, the interpolation function of the entire interval is obtained by splicing the interpolation functions on each sub-interval;

[0045] The piecewise cubic Hermite interpolation polynomial is:

[0046]

[0047] Wherein, x 0 and x 1 are two adjacent independent variables of the point to be interpolated, y 0 and y 1 are the dependent variables corresponding to x 0 and x 1 , and y' 0 and y' 1 are the corresponding first-order derivatives.

[0048] The calculation formula of the confidence level is as follows:

[0049]

[0050] Wherein, a is the confidence level, with the unit of dB, P 实测 is the power measurement value at the verification frequency point, and P 模型 is the theoretical calculation power value of the simulation model at the verification frequency point. The confidence level can be calculated through Equation (1).

[0051] The beneficial effect of the present invention is that when simulating an electromagnetic environment with a large frequency and power range, it is time-consuming and laborious to correct the simulation model error through actual measurement. Therefore, the present invention provides an electromagnetic environment simulation correction method combining the PCHIP method and measured data. By means of sampling, measurement, interpolation fitting and correction, the test amount required to correct the simulation model in actual engineering is reduced, and an electromagnetic environment simulation model that takes into account both accuracy and efficiency is established. The overall electromagnetic environment simulation correction process is as Figure 12 shown. It avoids a large number of experiments for verifying the model, simplifies the calculation process, and reduces the actual calculation amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is the modeling flowchart of the electromagnetic environment theoretical model of the present invention.

[0053] Figure 2 is the time-frequency characteristic diagram of the AM signal simulation of the present invention.

[0054] Figure 3 is the measured spectrum characteristic diagram of the injected AM signal of the present invention.

[0055] Figure 4 is the measured power at the sample point in the injected simulation case of the present invention.

[0056] Figure 5 is the relationship curve diagram of the transmitted power and received power at different frequency points in the injected simulation of the present invention.

[0057] Figure 6 is the schematic diagram of the darkroom radiation electromagnetic environment simulation scene of the present invention.

[0058] Figure 7 This is the measured spectrum feature diagram of the radiated AM signal of the present invention.

[0059] Figure 8 : Measured power at the sample point in the radiated analog case.

[0060] Figure 9 This is the curve diagram of the relationship between the transmitted power and the received power at different frequency points during the radiated simulation of the present invention.

[0061] Figure 10 This is the comparison diagram between the model simulation result and the measured result at the verification point in the injection simulation case of the present invention.

[0062] Figure 11 This is the comparison diagram between the model simulation result and the measured result at the verification point in the radiated simulation case of the present invention.

[0063] Figure 12 This is the flow chart of the electromagnetic environment simulation correction method of the present invention. Detailed implementation manners

[0064] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0065] The correction method for electromagnetic environment simulation based on PCHIP of the present invention includes the following steps:

[0066] Step 1: Model the electromagnetic environment;

[0067] The simulation of the electromagnetic environment includes injection simulation and anechoic chamber radiated simulation. Theoretical modeling is carried out separately for different environmental simulation methods; the parameters of the simulated electromagnetic environment are set according to the actual studied electromagnetic environment or according to the object to be modeled; the modeling process is to first determine the simulation model parameters of the electromagnetic environment, signal regime, signal frequency band, and signal power, and then establish a theoretical simulation model of the electromagnetic environment according to the corresponding signal regime; after establishing the theoretical simulation model of the electromagnetic environment, determine the sample size according to the random sampling principle and extract sample points within the frequency band range, and calculate the in-band average power value of the received signal at the sample points through the simulation model;

[0068] In this modeling, taking the simulation of the electromagnetic environment of AM regime signals as an example, the modeling steps for simulating the electromagnetic environment of other regime signals can be referred to Figure 1 .

[0069] (1) Injection simulation of the electromagnetic environment

[0070] Taking the electromagnetic environment of an AM signal with a frequency band of 1 to 8 GHz and a transmission power of -5 dBm to 5 dBm as an example, for other frequency bands and power ranges, refer to the establishment of the electromagnetic environment of the AM signal. First, determine the simulation model parameters of the model according to the modeling object, and then establish a mathematical model of the electromagnetic environment for the corresponding signal system;

[0071] The expression form of the AM signal is:

[0072] S AM (t) = [A 0 + m(t)]cos(2πf c t + φ) (2)

[0073] Where, A 0 is the DC level, m(t) is the baseband signal, that is, the original electrical signal, fc is the carrier frequency, is the initial phase;

[0074] The value range of m(t) is [-A m , +A m , then the modulation index of AM is:

[0075]

[0076] For the AM signal, the bandwidth calculation formula is:

[0077] B = 2R s (4)

[0078] Where, B is the bandwidth, R s is the baseband signal rate;

[0079] When performing mathematical modeling on the AM signal, when the in-band average power is set to 0 dBm, β AM = 20%, f c = 1 GHz, and the baseband signal rate is 1 MHz, the time-frequency domain characteristics of the AM signal are as Figure 2 shown;

[0080] In the frequency band of 1 to 8 GHz, sample points are selected at a sampling interval of 0.5 GHz, and other parameters remain unchanged. Calculate the signal power when the transmission power is 0 dBm. Based on the theoretical model, the in-band average power P rec of the signal is equal to the transmission power P tran minus the system loss P loss , that is:

[0081] P rec = P tran - P loss (5)

[0082] In the formula, P rec is the received signal power, Ptran is the transmitted signal power, P loss is the system loss;

[0083] (2) Radiative simulation in an anechoic chamber;

[0084] Similar to the injection simulation, taking the radiative AM signal electromagnetic environment with a frequency band coverage of 1 - 6 GHz and a transmitted power of 0 - 10 dBm as an example, the process of simulating the radiative electromagnetic environment of other systems, frequency bands, and power ranges can refer to Figure 1 .

[0085] The signal transmitted power is 10 dBm, the AM modulation index is β AM = 20%, the baseband signal rate is 1 MHz. Keeping the modulation index and the baseband signal rate unchanged, within the 1 - 6 GHz frequency band, sample points are selected at intervals of 0.25 GHz, and the signal power at a transmitted power of 10 dBm is calculated. Similar to the injection simulation method, the average in-band power of the signal during radiative simulation is equal to the transmitted power minus the system loss minus the path loss, that is:

[0086] P rec = P tran - P loss - P path (6)

[0087] where, P rec is the received signal power, P tran is the transmitted signal power, P loss is the system loss, P path is the path loss;

[0088] Step 2: Actual measurement

[0089] Actually measure the power value of the received signal at the sample frequency points, analyze the mathematical relationship between the frequency and the measured power, so as to correct the simulation model of the electromagnetic environment;

[0090] (1) Injection measurement

[0091] The instruments used in the actual measurement of the injection electromagnetic environment simulation are shown in Table 1. Use the instrument to generate a modulation signal, set the instrument parameters, so that the instrument generates a signal that is exactly the same as the signal system, frequency, transmitted power, and baseband signal rate in the injection simulation in Step 1. Use a spectrum analyzer to observe the frequency domain characteristics of the signal and compare them with the theoretical simulation frequency domain characteristics;

[0092] Table 1 Instruments and equipment for measurement

[0093]

[0094] Use an 8257D analog signal generator, set the modulation index to 20%, fc = 1 GHz, baseband signal rate 1 MHz, when the RF power is 0 dBm, the in-band average power measured using a spectrum analyzer is -0.82 dBm, and its spectral characteristics are as Figure 3 shown.

[0095] In the range of 1 - 8 GHz, the RF frequency is changed at intervals of 0.5 GHz, other parameters remain unchanged, and the FSQ26 spectrum analyzer measures the power, and the in-band average power of the received signal at the sample frequency points is obtained as Figure 4 .

[0096] It can be seen that when the input power remains constant, the measured output powers at different frequency points in the 1 - 8 GHz frequency band have obvious non-linearity.

[0097] Set the output power range of the signal source to -5 dBm to 5 dBm, change the output power of the signal source at intervals of 1 dBm, other parameters remain unchanged, use a spectrum analyzer to measure the in-band average power at 1 GHz, 2 GHz, 4 GHz, and 8 GHz, and obtain the output power of the signal source and the actually measured power by the spectrum analyzer as Figure 5 shown.

[0098] By actually measuring the power at the sample frequency points, analyze the mathematical relationship between the electromagnetic environment frequency and power under the actual measurement conditions, and based on this, model and correct the electromagnetic environment theoretical simulation model. As Figure 5 shown, in this embodiment, when the frequency is fixed and the transmitted signal power increases linearly, the received power increases linearly according to the slope k = 1. Therefore, the correction of the theoretical simulation model of the electromagnetic environment signal needs to refer to this relationship.

[0099] (2) Radiative measurement

[0100] The instruments used in the radiative electromagnetic environment simulation actual measurement are shown in Table 2, and modulation signals are generated using the instruments. Set the signal modulation method, frequency, power and other parameters to be consistent with the theoretical simulation, and use a spectrum analyzer to observe the signal frequency domain characteristics and compare them with the theoretical simulation frequency domain characteristics.

[0101] Table 2 Instruments and equipment used in the measurement

[0102]

[0103] The darkroom radiative electromagnetic simulation environment scene is as Figure 6 shown:

[0104] Using an 8257D analog signal generator, set the modulation index to 20%, f c = 1 GHz, baseband signal rate 1 MHz, when the transmit power is 10 dBm, the in-band average power measured using a spectrum analyzer is -43.18 dBm, and its frequency domain characteristics are asFigure 7 as shown

[0105] In the range of 1 - 6 GHz, with an interval of 0.25 GHz, the radio frequency is changed while other parameters remain unchanged. The FSQ26 spectrum analyzer measures the power, and the output power at different frequencies under experimental conditions is obtained as shown Figure 8 .

[0106] The output power of the signal source is changed while other parameters remain unchanged. The in - band average power measured by the spectrum analyzer at 1 GHz, 2 GHz, 4 GHz, and 6 GHz is recorded. The output power range of the signal source is set from 0 dBm to 10 dBm, with an interval of 1 dBm, and the relationship between the signal source output and the spectrum analyzer input is obtained as shown Figure 9 as shown

[0107] It can be seen that when the frequency is fixed and the transmitted signal power increases linearly, the measured received power at 1 GHz, 2 GHz, and 4 GHz increases linearly with a slope of k = 1, the measured received power at 5 GHz increases linearly with a slope of k = 0.853, and the measured received power at 6 GHz increases approximately linearly. Therefore, when correcting the theoretical model, it should be corrected according to this relationship

[0108] Step 3: Fit the simulation results based on the measured results and the PCHIP method

[0109] According to the measured data obtained from the injection - type measurement and the radiation - type measurement in Step 2, the in - band average power values of the received signals at n sample frequency points [P 1 , P 2 , … P n are obtained. According to the actually measured data, the theoretical in - band average power values of the received signals at the sample frequency points in the simulation model [P` 1 , P` 2 , … P` n are corrected so that the model - calculated power value at the sample points is equal to the measured power value, that is, P i = P` i , i = 1, 2, … n;

[0110] Using the PCHIP method and combining the mathematical relationship between the measured power and the frequency obtained in Step 2, the discrete power values [P` 1 , P` 2 , … P` n of the injection - type simulated electromagnetic environment simulation model and the radiation - type simulated electromagnetic environment simulation model are interpolated and fitted to obtain the in - band average power values of the received signals outside the sample frequency points within the simulation frequency band and power range;

[0111] Step 4: Confidence level test

[0112] Randomly select verification points within the frequency band and power range determined in Step 2. The absolute error between the signal reception power of the corrected simulation model at the verification points and the actually measured signal reception power should be within the confidence range. The value range of the confidence level is α ∈ [-0.5dB, 0.5dB]. When P 模型 and P 实测 's power difference is within the confidence level, it can be considered that the calculated power P 模型 of the model correction and the actually measured power P 实测 meet the confidence level requirements; if the absolute error between the signal reception power calculated by the theoretical model and the actually measured received signal power is greater than 0.5dB, that is, the absolute error is outside the value range of the confidence level, then the verification point is supplemented to the actually measured samples as a sample point, and then repeat Steps 1 to 3 until the verification points randomly selected by the theoretical model under the principle of random sampling meet the confidence level requirements, then the correction of the final theoretical model is completed.

[0113] (1) Results of the injection-type simulation correction

[0114] Randomly select verification points, as shown in Table 3.

[0115] Table 3 Verification points

[0116]

[0117] The correction results are as Figure 10 shown.

[0118] The corrected theoretical model meets the confidence level requirements at the verification points.

[0119] (2) Results of the radiation-type simulation correction

[0120] Randomly select verification points, as shown in Table 4.

[0121] Table 4 Verification points

[0122]

[0123] The correction results are as Figure 11 .

[0124] The corrected theoretical model meets the confidence level requirements at the verification points.

[0125] The specific steps of PCHIP interpolation in Step 3 mentioned above are as follows:

[0126] The piecewise cubic Hermite interpolation (PCHIP) method not only satisfies the equality of function values at the nodes but also satisfies the equality of the first derivative values at the nodes. Therefore, the fitted curve will be smoother and the accuracy will be higher.

[0127] Arrange the actually measured sample points in ascending order of frequency, denoted as [x0 , x 1 , x 2 , …, x n , the measured power at the corresponding frequency points is recorded as [y 0 , y 1 , y 2 , …, y n , where x 0 ≤ x 1 ≤ … ≤ x n ;

[0128] Based on the piecewise interpolation idea, by continuously performing piecewise cubic Hermite interpolation (PCHIP) between adjacent two sample points, and finally obtaining the interpolation function of the entire interval by splicing the interpolation functions on each sub - interval;

[0129] The piecewise cubic Hermite interpolation polynomial is:

[0130]

[0131] In the formula, x 0 and x 1 are two independent variables adjacent to the point to be interpolated, y 0 and y 1 are the dependent variables corresponding to x 0 and x 1 , and y' 0 and y' 1 are the corresponding first - order derivatives.

[0132] The calculation formula of the confidence level is as follows:

[0133]

[0134] where a is the confidence level, in units of dB, P 实测 is the power measurement value at the verification frequency point, P 模型 is the theoretical calculation power value of the simulation model at the verification frequency point, and the confidence level can be calculated through Equation (1).

Claims

1. A correction method for electromagnetic environment simulation based on PCHIP, characterized in that it includes the following steps: Step 1: Model the electromagnetic environment; The simulation of the electromagnetic environment includes injection simulation and anechoic chamber radiation simulation. Theoretical models are established separately for different environmental simulation methods; The parameters of the simulated electromagnetic environment are set according to the actual studied electromagnetic environment or according to the object to be modeled; The modeling process is to first determine the simulation model parameters of the electromagnetic environment, signal system, signal frequency band, and signal power, and then establish a theoretical simulation model of the electromagnetic environment according to the corresponding signal system; After establishing the theoretical simulation model of the electromagnetic environment, determine the sample size according to the random sampling principle and extract sample points within the frequency band range, and calculate the in-band average power value of the received signal at the sample points through the simulation model; Step 2: Actual measurement Actually measure the power value of the received signal at the sample frequency points, analyze the mathematical relationship between the frequency and the measured power, so as to correct the simulation model of the electromagnetic environment; Step 3: Fit the simulation results based on the measured results and the PCHIP method; According to the measured data obtained in the injection measurement and the radiation measurement in Step 2, the in-band average power values of the received signals at n sample frequency points [P 1 , P 2 , … P n are obtained. According to the actually measured data, the in-band average power values of the theoretical received signals at the sample frequency points in the simulation model [P` 1 , P` 2 , … P` n are corrected so that the model-calculated power values at the sample points are equal to the measured power values, that is, P i = P` i , i = 1, 2, … n; Using the PCHIP method, combined with the mathematical relationship between the measured power and frequency obtained in step two, interpolate and fit the discrete power values [P` 1 , P` 2 , … P` n of the injection-type simulated electromagnetic environment simulation model and the radiation-type simulated electromagnetic environment simulation model, so as to obtain the average power value within the received signal band outside the sample frequency points within the simulation frequency band and power range; Step 4: Confidence level test Randomly extract verification points within the frequency band and power range determined in Step 2. The absolute error between the signal reception power of the corrected simulation model at the verification points and the actually measured signal reception power should be within the confidence range, and the value range of the confidence is α ∈ [-0.5dB, 0.5dB]. When P 模型 and P 实测 's power difference is within the confidence, it can be considered that the calculated power P 模型 and the measured power P 实测 meet the confidence requirements; if the absolute error between the signal reception power calculated by the theoretical model and the actually measured received signal power is greater than 0.5dB, that is, the absolute error is outside the confidence value range, then the verification point is supplemented to the measured samples as a sample point, and then repeat Steps 1 to 3 until the verification points extracted by the theoretical model under the principle of random sampling meet the confidence requirements, then the correction of the final theoretical model is completed.

2. The correction method for electromagnetic environment simulation based on PCHIP according to claim 1, characterized in that: In the said Step 1, if an AM system signal electromagnetic environment is adopted, then: (1) Injection simulation of the electromagnetic environment; First, determine the simulation model parameters of the model according to the object to be modeled, and then establish a mathematical model of the electromagnetic environment corresponding to the signal system; The expression form of the AM signal is: S AM (t) = [A 0 + m(t)] cos(2πf c t + φ) (2) where A 0 is a DC level, m(t) is a baseband signal, i.e., the original electrical signal, and fc is the carrier frequency, is the initial phase; The value range of m(t) is [-A m , +A m . Then the modulation index of AM is: For the AM signal, the bandwidth calculation formula is: B = 2R s (4) Among them, B is the bandwidth, and R s is the baseband signal rate; Mathematically model the AM signal. Within the frequency band of the determined model of the AM signal, select sample points at a sampling interval of f 1 Hz, keep other parameters unchanged, and calculate the signal power of the transmitted power. The average power P rec within the signal band is equal to the transmitted power P tran minus the system loss P loss , that is: P rec = P tran -P loss (5) Where, P rec is the received signal power, P tran is the transmitted signal power, and P loss is the system loss; (2) Anechoic chamber radiation simulation of the electromagnetic environment; Keeping the modulation index and the baseband signal rate unchanged, within the frequency band of the AM signal determination model, sample points are selected at intervals of f 2 Hz, and the signal power of the transmitted power is calculated. The average in-band power of the signal during radiative simulation is equal to the transmitted power minus the system loss minus the path loss, that is: P rec = P tran - P loss - P path (6) Among them, P rec is the received signal power, P tran is the transmitted signal power, P loss is the system loss, and P path is the path loss.

3. The correction method for electromagnetic environment simulation based on PCHIP according to claim 1, characterized in that: In the said Step 2, the measurement steps are: (1) Injection measurement During the actual measurement of the injection simulation of the electromagnetic environment, use the instrument to generate a modulation signal, set the instrument parameters, so that the instrument generates a signal that is exactly the same as the signal system, frequency, transmission power, and baseband signal rate in the injection simulation in Step 1, and use the spectrum analyzer to observe the frequency domain characteristics of the signal and compare them with the theoretical simulation frequency domain characteristics; Within the frequency band of the AM signal determination model, change the radio frequency at intervals of f 1 Hz, keep other parameters unchanged, measure the power, and obtain the average in-band power of the received signal at the sample frequency points; Set the output power range of the signal source, change the output power of the signal source at intervals of 1 dBm, keep other parameters unchanged, and use the spectrum analyzer to measure the in-band average power to obtain the output power of the signal source and the actually measured power of the spectrum analyzer; (2) Radiation measurement During the actual measurement of the anechoic chamber radiation simulation of the electromagnetic environment, use the instrument to generate a modulation signal, set parameters such as the signal modulation method, frequency, and power to be consistent with the theoretical simulation, and use the spectrum analyzer to observe the frequency domain characteristics of the signal and compare them with the theoretical simulation frequency domain characteristics; Within the frequency band of the AM signal determination model, change the radio frequency at intervals of f 2 Hz, keep other parameters unchanged, measure the power, and obtain the output power at different frequencies under experimental conditions; Change the output power of the signal source, change the output power of the signal source at intervals of 1 dBm, keep other parameters unchanged, record the in-band average power of the spectrum analyzer, and obtain the relationship between the signal source output and the spectrum analyzer input.

4. The correction method for electromagnetic environment simulation based on PCHIP according to claim 1, characterized in that: The specific steps of PCHIP interpolation in the said Step 3 are as follows: Arrange the actually measured sample points in ascending order of frequency, denoted as [x 0 , x 1 , x 2 , …, x n . The actually measured power at the corresponding frequency points is denoted as [y 0 , y 1 , y 2 , …, y n . Among them, x 0 ≤ x 1 ≤ … ≤ x n ; By continuously performing piecewise cubic Hermite interpolation between adjacent two sample points, and finally splicing the interpolation functions on each sub-interval, the interpolation function of the entire interval is ultimately obtained; The piecewise cubic Hermite interpolation polynomial is: where x 0 and x 1 are two adjacent independent variables of the point to be interpolated, y 0 and y 1 are the dependent variables corresponding to x 0 and x 1 , and y' 0 and y' 1 are the corresponding first-order derivatives.

5. The correction method for electromagnetic environment simulation based on PCHIP according to claim 1, characterized in that: The calculation formula of the confidence level is as follows: Among them, a is the confidence level, with the unit of dB, and P 实测 is the power measurement value at the verification frequency point, and P 模型 is the theoretical calculated power value of the simulation model at the verification frequency point, and the confidence level can be calculated through Equation (1).

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