Study on characteristics of electromagnetic coupling into annular aperture based on FDTD

To enhance the stability of the electronic system in complex electromagnetic environment, the characteristics of electromagnetic pulse(EMP) with different pulse width coupling into annular apertures with different shapes(square, circle and rectangle) were analyzed by the finite-difference time-domain method(FDTD). It shows that, the coupling phenomenon of electromagnetic pulse into annular apertures is obvious, and the coupling energy of the electromagnetic pulse into the circular annular aperture is smallest than the square and the rectangular ones. To the rectangular annular aperture, while the polarization direction of the incident pulse is parallel to the short side of the aperture, the coupling energy is larger when the aspect ratio of the rectangular annular aperture is larger, and the coupling energy is smaller when the aspect ratio of the rectangular annular aperture is larger while the polarization direction of the incident pulse is perpendicular to the short side of the aperture.The shorter the pulse width is, the easier the electromagnetic pulse coupling into annular apertures is. The coupling effect is enhanced by the reflection and the resonance of the cavity.