Research On Theoretical Modeling And Calculation Methods For The Electromagnetic Coupling Effect Of Complex Enclosures

The electromagnetic compatibility(EMC)of electrical and electronic equipment has become more and more critical because of the increasingly complex electromagnetic environment.Electromagnetic shielding is an important technology for effectively suppressing the electromagnetic interference(EMI).The system equipment has become more and more sophisticated due to the highly integration of electrical and electronic system equipment and the diversification of methods for the improvement of the shielding effectiveness(SE).In order to analyze the EM coupling effect and calculate the EM coupling characteristics of complex enclosures rapidly and accurately,this paper has studied the EM coupling problems for the electrically small apertured enclosures embedded dielectric plates,the enclosures with electrically large apertures,the transmission line(TL)in multiple enclosures with apertures covered by conductive materials,and the penetrated TL in cascaded enclosures with hybrid apertures.To solve the above models,the corresponding analytical calculation model has been proposed,which provide a theoretical basis for the design of the EM shielding of complex enclosures.Specifically,the research includes the following contents:(1)Study on the extension the Baum-Liu-Tesche(BLT)analytical method for the SE of the electrically small apertured enclosureSince the BLT analytical method can hardly deal with off-axis aperture arrays and arbitrarily positioned monitor points simultaneously,and the calculation error is large,the aperture position coefficient of the equivalent circuit method is introduced into the BLT method,and the relation between the voltage on the centerline and the electric field at any point in the enclosure is established based on the waveguide theory.An accurate BLT extended method has been derived for predicting the SE of arbitrarily positioned aperture arrays and monitor points,and the resonant modes in high frequencies.The full wave EM simulation softwave CST(Computer Simulation Technology)is used to validate the extended BLT method.The extended BLT method is applied to handle the case of the enclosure with off-axis aperture arrays on opposite faces and multiple cascaded apertured enclosures,which also possesses high calculation accuracy.(2)Study on the analytical method for the SE of the apertured enclosure embedded dielectric platesSince the calculation accuracy of the equivalent circuit method in high frequencies in low,and in order to compare and analyze the effect of the dielectric plate on the SE and the resonance in high and low frequency,an analytical model has been proposed for the accurate prediction of the SE of the apertured enclosure embedded dielectric plates in high frequencies.Firstly,the dielectric plate is equivalent to lossy waveguide and the equivalent circuit of the apertured enclosure embedded dielectric plates is established based on the waveguide theory and the circuit principle.Then,the scattering and propagation matrices corresponding to the equivalent circuit of the dielectric plate are derived by employing the microwave circuit theory.Finally,based on the extended BLT method,the SE at any point in the enclosure embedded dielectric plates with arbitrarily positioned apertures is computed.The validation of the analytical model is examined by the CST.The analytical model can rapidly compare and analyze the effect of dielectric plate parameters,including the position,the thickness,the conductivity,and the relative permittivity on the SE and the resonances.In addition,the analytical model is further extended to predict the SE of heterotypic apertured enclosure embedded dielectric plates by analyzing the EM energy transmission of discontinuous waveguide structures and deriving the scattering matrix.(3)Study on the analytical method for the SE of the electrically large apertured enclosureThe electrical size of the aperture becomes larger with the increase of the frequency,resulting in the decrease of the calculation accuracy of the equivalent circuit method and the BLT method.To solve it,an analytical model has been proposed for accurately predicting the SE and the resonant modes of electrically large apertured enclosure.Firstly,based on the modified small hole coupling theory,the equivalent dipole moment of the electrically large aperture is computed.Then,based on the mirror procedure,the total vector potential is obtained according to the relation between the dipole moment and the vector potential.Finally,the electric field with the SE at any point inside the enclosure is derived by using the radiation field formulation of the vector potential.The CST is used to validate the analytical method proposed.The analytical model can deal with electrically large aperture of different sizes and shapes by replacing the polarizability of the aperture,and can also handle hybrid multiple apertures of different arrangements by the superposition of the electric field at the monitor point through each electrically large aperture,which is not restricted to the case of a single electrically large aperture and electrically large aperture of single shape.(4)Study on the analytical method for the EMI of the loads of the TL in double enclosures with apertures covered by conductive sheetsDue to the large dimension span of the TL and the covered enclosure,it costs great time to analyze the EM field coupling with the TL in double enclosures through covered apertures by using the traditional numerical methods.To solve it.this problem is decomposed into two independent sub-problems based on the electromagnetic topology(EMT)theory:the covered apertures coupling problem and the coupling problem between the enclosure field and the isolated TL.For the first sub-problem,the coupled electric field in double enclosures is calculated using the transfer impedance of the covered conductive sheets and the enclosure dyadic Green’s function.For the second sub-problem,the electric current induced at the termination loads of the TL is calculated by the obtained coupled electric field and the equivalent π circuit of the TL combined with the Agrawal’s model.Consequently,an analytical model is presented for the rapid calculation of the EMI of the loads of the TL in double enclosures with multiple covered apertures.The analytical model is validated by the CST,and is then employed to analyze the effect of different parameters on the induced current,including the conductivity of the conductive sheets,and the position,the direction and the loads impedance.Finally,the analytical model is extended to deal with the EMI of the TL in double enclosures with covered aperture arrays on multiple sides.(5)Study on the analytical method for the EMI of the loads of the TL penetrating the apertured enclosureDue to the demand for power supply and data transmission of electrical and electronic equipment,usually the apertured enclosure is penetrated by a TL.Compared with the TL in the enclosure,penetrated line additionally provides conduction coupling path for the external EMI into the enclosure,causing more complex EM coupling.To solve it,an analytical model is presented for rapidly analyzing the EMI of the loads of the TL penetrating into an enclosure with electrically large aperture excited by a plane wave.Firstly,based on the EMT theory,the whole coupling problem is decomposed topologically and the main interference path is ascertained.Then,the obtained electric field in the em pty electrically large apertured enclosure by the modified small hole coupling theory and mirror procedure as well as the Agrawal’s model is used to calculate the excitation function of the penetrated TL of each interference path.Finally,the generalized BLT equation is employed to compute the electric current induced at the termination loads of the penetrated TL.For the case of hybrid apertured cascaded enclosures by a line penetration,in order to further simplify the derivation process,the coupling electric field in each enclosure is calculated,and the induced current of the loads is obtained using the equivalent π circuit of the TL combined with the Agrawal’s model.The validation of the above analytical models is examined by the CST.