Aerospace structures can be approximately modeled as a combination of canonical structures such as cylinder,cone and ellipsoid.Thus the RCS estimation of such canonical structures is of prime interest.Furthermore meta...Aerospace structures can be approximately modeled as a combination of canonical structures such as cylinder,cone and ellipsoid.Thus the RCS estimation of such canonical structures is of prime interest.Furthermore metamaterials possess peculiar electromagnetic properties which can be useful in modifying the RCS of structures.This paper is aimed at calculating the RCS of an infinitely long PEC circular cylinder coated with one or two layers of metamaterial.The incident and scattered fields of coated cylinder are expressed in terms of series summation of Bessel and Hankel functions.The unknown coefficients of summation are obtained by applying appropriate boundary conditions.The computations are carried out for both principal polarizations.The computed results are validated against the numerical-based method of moments.Further,the variation of RCS of the metamaterial coated PEC cylinder with material parameters,frequency,aspect angle and polarization is analyzed.展开更多
Electromagnetic tomography(EMT) is a non-invasive imaging technique capable of mapping the conductivity and permeability of an object. In EMT, eddy currents are induced in the object by the activation coils,and the re...Electromagnetic tomography(EMT) is a non-invasive imaging technique capable of mapping the conductivity and permeability of an object. In EMT, eddy currents are induced in the object by the activation coils,and the receiving coils can measure the EMT voltages. When the activation frequency is significantly large, we can treat the metallic targets as electrically perfect conductors(EPCs). In this situation, a thin skin approximation is reasonable and this type of scattering problem can be effectively treated by the boundary element method(BEM)formulated through integration equations. In this study, we compute three-dimensional(3D) sensitivity matrix between the sensors due to an EPC perturbation. Efficiency improvement is achieved through the utility of scalar magnetic potential. Two EPC objects, one sphere and one cube shaped, are simulated. The results agree well with the H dot H formula. Overall, we conclude that BEM can be used to calculate the 3D sensitivity matrix of an EMT system efficiently. This method is a general one for any shaped objects while the H dot H solution is only capable of producing the response for a small ball.展开更多
文摘Aerospace structures can be approximately modeled as a combination of canonical structures such as cylinder,cone and ellipsoid.Thus the RCS estimation of such canonical structures is of prime interest.Furthermore metamaterials possess peculiar electromagnetic properties which can be useful in modifying the RCS of structures.This paper is aimed at calculating the RCS of an infinitely long PEC circular cylinder coated with one or two layers of metamaterial.The incident and scattered fields of coated cylinder are expressed in terms of series summation of Bessel and Hankel functions.The unknown coefficients of summation are obtained by applying appropriate boundary conditions.The computations are carried out for both principal polarizations.The computed results are validated against the numerical-based method of moments.Further,the variation of RCS of the metamaterial coated PEC cylinder with material parameters,frequency,aspect angle and polarization is analyzed.
基金the National Natural Science Foundation of China(No.50937005)the Shanghai Maritime University Science and Technology Program(No.20120064)
文摘Electromagnetic tomography(EMT) is a non-invasive imaging technique capable of mapping the conductivity and permeability of an object. In EMT, eddy currents are induced in the object by the activation coils,and the receiving coils can measure the EMT voltages. When the activation frequency is significantly large, we can treat the metallic targets as electrically perfect conductors(EPCs). In this situation, a thin skin approximation is reasonable and this type of scattering problem can be effectively treated by the boundary element method(BEM)formulated through integration equations. In this study, we compute three-dimensional(3D) sensitivity matrix between the sensors due to an EPC perturbation. Efficiency improvement is achieved through the utility of scalar magnetic potential. Two EPC objects, one sphere and one cube shaped, are simulated. The results agree well with the H dot H formula. Overall, we conclude that BEM can be used to calculate the 3D sensitivity matrix of an EMT system efficiently. This method is a general one for any shaped objects while the H dot H solution is only capable of producing the response for a small ball.
