| According to the rat electromagnetic model, the electric field distribution within the rat's body including heart, brain and liver, were simulated respectively using FDTD method, under the irradiation of 2.71GHz and 9.33GHz high power pulse microwave (HPPM) from the direction of back, abdomen, side, head and tail. The influence on the morphology of rats'heart, caused by the radicalization of 2.71GHz HPPM from head direction and 9.33GHz HPPM from back direction, was studied. The relationship between electric field distribution obtained by numerical simulation and experimental results was analyzed. Furthermore, the Dose-effect relationship of biological effects of pulsed microwave was theoretically analyzed and discussed.Numerical simulation results show that, under the same electric field irradiation, the electric field distribution within the rat's body lied on the frequency of incident wave and radiation direction. Because the skin depth under 2.71 GHz HPPM was greater than the counterparts under 9.33GHz HPPM, after 2.17GHz HPPM irradiation from the five directions, the electric field within the rat's body was higher. The maximum electric field strength within the heart was the highest when the rat was radiated from abdomen and side direction. The mean and maximum electric field strength within the brain were the highest when the rat was radiated from back, tail and head direction. The mean electric field strength within the brain was the highest among the three organs and the electric field strength in lower part of the brain was higher than other regions. Because the skin depth under 9.33GHz HPPM was comparatively small, after 9.33GHz HPPM irradiation from the five directions, the electric field strength within the rat's body was small. The mean electric field strength of the whole body was obviously higher than the counterparts within heart and liver. And the mean electric field strength of the whole body approximated to the counterpart within brain. Moreover, the electric field strength in cortical region was higher than other regions.The experimental results show that, after 2.17GHz HPPM irradiation from the head direction, the injury of the left ventricular intima correlated with the pulse numbers. However, no significant injury was observed in left ventricular adventitia. It also shows that, after 9.33GHz HPPM irradiation from the back direction, there was no significant injury in left ventricular intima and adventitia. To a certain extent, the injury was nothing to do with the external pulsed electric field strength.The comparison of numerical simulation results and experimental results shows that damage effect appeared in the region of heart with higher electric field strength (E≥8.1kv/m), and it did not appear in the region of heart whose electric field strength(E≤2.8kv/m) was low.The numerical simulation results and experimental results show that, with the same external pulsed electric field strength and microwave frequency, the electric field distribution within the rat's body was changed when the irradiation direction was changed. With the same external pulsed electric field strength and irradiation direction, the electric field distribution within the rat's body was changed when the microwave frequency was changed. And with the same external pulsed electric field strength, irradiation direction and microwave frequency, the electric field distribution in different regions of the same organ differed. The damage effect caused by the electric field distribution was also different. All the results show that, when the wavelength approximated to the size of the irradiated object, electromagnetic dose-effect relationship could not be described by the radiation dose in vitro(such as average power density), as well as the average radiation dose in vivo(such as the average SAR in vivo). It must be described by local radiation dose in vivo. In this paper, numerical simulation method was developed, and its correctness was verified by experiments. This method was reasonable and reliable for the study of human biological effects caused by electromagnetic radiation and electromagnetic radiation safety limits on the human body.
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