A novel model is proposed to analyze the scattering of antenna
which gives the structural mode RCS and antenna mode RCS eparately. The phase difference between the two modes, which is difficult to simulate, is solved with the model. The scattering of antenna with arbitrary load is obtained conveniently from the model results. The model is realized by the ANSOFT HFSS and some useful results are illustrated. The structural mode RCS and antenna mode RCS are compared with the results by other methods, which proves the model correct and efficient. The results are meaningful for the antenna RCS prediction and reduction.