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Abstract
As to the technology requirements of electromagnetic compatibility and protection performance test for system, considering the problems existed in traditional electromagnetic susceptibility test method, we put forward an electromagnetic radiation safety margin test method combined injection with radiation. Considering the equal response voltage on the equipment input port as equivalent principle rather than the distributive current on the cable, the equivalence between injection and radiation was theoretically analyzed. By adopting antisymmetric directional coupler cascade design scheme, the S parameter of coupling module with six ports was calculated. Moreover, the effect test method of using injection as an equivalent substitute for radiation based on coupling module was put forward. The typical antenna receiving system was selected as equipment under test. By carrying out injection and radiation effect test, under the condition of equal output response, the curvilinear relation between radiated field intensity and injection voltage was determined. The validity of electromagnetic radiation safety margin test method combined injection with radiation was verified.
... The research on margin has mainly focused on test method and equipment level or critical circuits [3][4][5] , or statistical method evaluation [6] , safety margin design [7] , etc. However, for large-scale complex systems such as ships and airplanes, which are integrated with a variety of equipment, the electromagnetic energy coupling relationship is complex, and the verification methods of various types of EME vary widely [8] . ...
... For the high-intensity electromagnetic field, in addition to the radiation method, the injection method [5] and other equivalent method [25] can also be used. Choosing appropriate injection test method can ensure the consistency of injection and radiation test results, as shown in Fig.8. ...
Margin is an important index in the control of Electromagnetic environmental effects (E3) and Electromagnetic compatibility (EMC) design for systems. How to define and verify the E3 margins of complex systems such as ships and airplanes is a difficult problem. A new method of system‐level E3 margin evaluation is proposed. Based on the theory of fault tree, the evaluation model of system‐level margin is constructed. The complex system function is transformed into the equipment and subsystem that affect the function, and the relationship between margin of system‐level and equipment is established. The change from margin of equipment to system‐level margin is realized. According to the action process of Electromagnetic environment (EME), the verification and evaluation methods of EME domain, response domain and effect domain are put forward. The margin calculation formula of EME domain and typical electromagnetic energy coupling response are deduced. The problem of margin evaluation for equipment under different input parameters is solved. A typical application example is given. The verification test scheme is designed. The methods of electromagnetic energy radiation and injection are adopted. The system‐level margin is analyzed by the data obtained from the effective test verification. The results show that the model and method are reasonable and feasible.
For studying the coupling effect of electromagnetic irradiation to rectangular enclosure with wire penetration, a new hybrid model is proposed to determine the shielding effectiveness of the enclosure. This model based on rectangular-enclosure equivalent circuit regards the penetrating wire as a monopole antenna, and the frequency-domain results of calculation using this model match with that of computer simulation technology (CST) Microwave Studio. Meanwhile, this new model requires far less computation than traditional methods: 3 s for one sample on an average personal computer. Based on the presented model, the relationships between enclosure volume, external length of wire penetration, internal length of wire penetration, and shielding effectiveness are analyzed. In the frequency range from 100 MHz to 1 000 MHz, when keeping the length of penetrating wire unchanged, the shielding effectiveness of an enclosure at its center point increases with the cavity volume. There is no obvious effect from the external length of penetrating wire on the shielding effectiveness. If the external length of a penetrating wire is 8 cm unchanged, the shielding effectiveness of the penetrated enclosure at its center point declines with the increase of internal length of the penetrating wire.
There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously, a double differential-mode current injection test method (DDMCI) is proposed. The method adopted the equivalence source wave theorem and Baum-Liu-Tesche(BLT) equation as its theory foundation. The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived, and the phase relation between the two injection voltage sources is confirmed. The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device, the transmission line length, and the source vector in BLT equation, but has nothing to do with the reflection coefficient between the two equipment pieces. Therefore, by choosing the right amplitude and phase of the double injection voltage sources, the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.
In order to study electromagnetic field coupling to irregular cuboid enclosures, tests of shielding effectiveness are performed using a hollow irregular truncated pyramid with a square aperture. The electric field distribution inside the enclosure with different sizes of the square aperture is measured within the frequency range of 5-1000 MHz. The experimental results are in a good agreement with the stimulation results obtained by using computer simulation technology (CST) code. It is shown that the aperture size affects shielding effectiveness at low frequencies, at which shielding effectiveness decreases with the decreasing aperture size. The effect of the aperture size vanishes and shielding effectiveness improves by more than 12 dB when polyurethane absorbent fills the enclosure.
In order to theoretically analyze and calculate induced current on cable caused by space electromagnetic field coupling, we obtained the analytic expression of the induced current for different terminal loads of cable by using the transmission line model with a distributed source of aerial shielded cable-ground circuit. Then we analyzed the resonance mechanism of induced current, and acquired the relationship between resonance frequency and cable's length. Additionally, we discussed the relationship among induced current resonance, ground conductivity, and cable's overhead height. The results show that, when resonance occurs in the induced current, its amplitude increases with the cables-ground circuit's time constant. Under preconditions including earth conductivity of 0.01 S/m, irradiation wave frequency of 75 MHz, cable radius of 4 mm, height between cable and ground of 1 m, cable length of 2 m, and both ends of cable being overhead, error between the theoretically calculated result and measured result of the cable induced current is below 5 dB.
Aim
To use recent information of infant and cancer mortality in Alabama counties of the USA to test their relationships with social, economic, and environmental conditions at a large scale to identify potential public health issues.
Subjects and methods
The data of infant mortality rates and cancer deaths in the recent years, biodiversity, including species number of plants, fishes, reptiles, and amphibians, roadless areas, metropolitan areas, river basins, African-American and minority populations, and per person income for all 67 Alabama counties were obtained and organized by geographic information system. The relationships between infant mortality rates and cancer deaths and social, economic, and environmental conditions at a large scale were analyzed.
Results
Infant mortality was significantly higher in African-American and other minority populations than in white populations, but cancer mortality was higher in white populations than in African-American and minority populations. There was no significant difference in infant mortality rate between populations in the urban areas and the rural areas, but the mortality rate of cancers was significantly higher in the rural population than in the urban population. Mortality rates for cancers in wealthy counties were lower than in poorer counties. The incidences of infant and cancer mortality were lower in counties with higher biodiversity. The emergent spatial pattern suggests that the incidences of infant and cancer mortality were higher in the Sipsey/Warrior River Basin, Coosa/Tallapoosa River Basin, and Conecuh River Basins.
Conclusion
This study indicates that ethnic disparities in infant and cancer mortality still exist in Alabama. This study also suggests that pattern analyses at larger scales can provide new insight for understanding public health.
Simulation of EMP effects of electronic equipment becomes an important means for electromagnetic compatibility (EMC) design. In accordance with the universally existing complex computing process problems in mechanism modeling algorithm ubiquity, the application of least squares support vector regression(LSSVR) in modeling algorithm of EMP field coupling on electronic devices has been researched. In order to improve the precision of electromagnetic pulse (EMP) energy coupling model, to prevent signal distortion, and to retain the high frequency details of EMP signal, the method of wavelet shrinkage de-noising is used to process the measured signal. Through the coupled voltage data of the rectangular pulse field induced by regulated power supply in the GHz Transverse electromagnetic (GTEM) and LSSVR modeling transfer function of energy coupling, the parameters of the model are optimized based on two typical algorithms such as simulated annealing algorithm(SAA) and genetic algorithms(GA), and the model of the coupled voltage simulation is used in prediction. By comparing the two important parameters -the GOF(Goodness of Fit) and the MSE(Mean Square Error) of regression capacity of characterized model, the results show that data by SA parameter optimization LSSVR model fit with the actual ones, and the LSSVR model is proved to be an effective means of engineering simulation modeling with a smaller MSE and simplified computing process.
In this paper, possible applications of double bulk current injection for susceptibility testing of spacecraft are investigated and discussed. Two test procedures are proposed: one is suitable for system-level (i.e., onboard) testing, the other for unit-level assessment of avionic equipment interconnected by multiwire shielded bundles. By enforcing equivalence between radiation and injection, both procedures are designed to inject expected electromagnetic interference (EMI) levels in the equipment under test (EUT), connected at the terminations of a wiring harness. The procedure for system-level testing requires amplitude and phase control of the radio-frequency power sources used to feed the injection probes. It allows to correlate the susceptibility effects obtained by injection with those due to a nonuniform electromagnetic field (such as the field generated by internal EMI sources in metallic enclosures). It is, therefore, suited for radiated intrasystem verifications. The procedure for unit-level testing exploits equivalence between radiation and injection in terms of the current distribution along the overshield, and applies to bundles with an arbitrary number of inner conductors. In the case of vertical polarization, this procedure allows for the reconstruction of the interference effects produced in the EUT by conventional radiated-susceptibility tests (e.g., DO-160), requiring direct radiation of the system.
The direct current injection (DCI) method, sometimes also referred to as direct drive, for aircraft high-intensity radiated field (HIRF) certification is evaluated. The method aims at reducing the necessity of resource-intensive radiated field testing at frequencies below the very high frequency band. Surface currents of a fuselage model are evaluated both analytically for incident fields and using DCI techniques. Resulting conductor currents occurring inside the fuselage model are measured and compared for both the incident field and DCI measurement techniques. The comparison approach is a direct one, meaning that no transfer function is applied between the methods.
Field excitation and bulk current injection (BCI) on a wire bundle
are analytically compared. The equivalence of the two excitation
techniques is investigated in order to ascertain the validity of using
current injection testing rather than radiated immunity testing for an
equipment connected at one end of the bundle. The wire bundle is modeled
as a multiconductor transmission line which, throughout the analysis, is
treated as a multiport device. The equivalence is discussed by comparing
the effects that the sources produce at the terminal ports, with the aim
to control the clamp voltage in order to match the incident field
characteristics. This approach yields general results, which are not
affected by any assumptions on the terminal networks. It is shown that
one injection probe is not sufficient to assure the equivalence in the
general case, but it is possible, although practically difficult, to
achieve this result by employing two injection probes. In the simpler
but more specific case of linear terminations, a test procedure is
proposed which allows equivalence by using a single injection current
probe. Since the ideal BCI procedure must represent a worst-case stress
analysis for the equipment under test, the possibility of adopting BCI
tests to reproduce the upper envelope of the radiation-induced currents
is also investigated. In this case practical difficulties are evidenced
and arise from the need of feeding the injection probes with a
complicated frequency-dependent power distribution