In order to improve the power capacity of the high power microwave(HPM)radiation antenna,a radiation antenna window with grading ring is designed.With grading ring in antenna window can avoid dielectric window breakdown effectively.Changing the electric field distribution of the dielectric window leads to the electron trajectory change.CST simulation shows that when the grading ring is perpendicular to electric field,it does not affect the radiation of the antenna.According to the output microwave character...