He S
Department of Electromagnetic Theory, Royal Institute of Technology, Stockholm, Sweden.
IEEE Trans Biomed Eng. 1998 Oct;45(10):1249-58. doi: 10.1109/10.720203.
The electromagnetic field generated by a current dipole situated at an arbitrary position inside a conducting sphere is derived using the expansions of the spherical vector wave functions. The first few terms in a series expansion of this field with respect to the frequency are given for the normal magnetic field (used in magnetoencephalogram) and the tangential electric field (used in electroencephalogram) outside the conducting sphere at low frequency. It is shown that the first correction term to the static solution is linear in the frequency omega (the second correction term is proportional to omega 3/2) and, thus, the static solution can be used as a good approximation for the solution at a very low frequency.
利用球矢量波函数的展开式，推导了位于导电球体内任意位置的电流偶极子产生的电磁场。给出了该场在低频时关于频率的级数展开式中的前几项，用于导电球体外的正常磁场（用于脑磁图）和切向电场（用于脑电图）。结果表明，静态解的一阶修正项与频率ω成线性关系（二阶修正项与ω的3/2次方成正比），因此，静态解可作为极低频率下解的良好近似。
