时域有限差分法连接边界电磁泄漏

Connective boundary's electromagnetic leakage in finite-difference time-domain

用时域有限差分法计算目标的雷达散射截面时,一般用连接边界来引入平面入射波.理想情况下,当总场区没有散射目标时,该区域仅有入射波,散射场区电磁波为0.但在实际计算过程中,散射场区的电磁波一般不会严格等于0,这是因为在连接边界引入入射波时产生了电磁泄漏.一维情形下,用散射场区电场的平方和来衡量电磁泄漏程度.二维情形下,用等效原理将散射场区的电磁场进行远场外推,得到雷达散射截面,以此衡量电磁泄漏的大小.研究表明:时间步长、入射角度都能影响电磁泄漏大小.为使电磁泄漏较小,时间步长应接近于稳定性要求的最小步长,入射方向应避免垂直于计算区域边界.

When calculating target＇s radar cross section（RCS） with finite-difference time-domain（FDTD）,the incident wave was induced using connective boundary.In ideal situation without scattering target,there is only incident wave in total field region and the field in scattering field region is zero.But in practical calculating process,the electromagnetic wave in scattering field region is not rigidly zero because of leakage in connective boundary.In 1-dimensional situation,the leakage was measured by sum of squared electric field.In 2-dimensional situation,the leakage was measured by RCS which acquired by far field transformation of electromagnetic field in scattering field region using equivalent principle.Research results show that time step and incident angle influence the leakage very much.The leakage is small when the time step is near the least step needed for the stable requirement and the incident direction avoids impinging the connection boundary perpendicularly.