Electromagnetic-wave visualization for EMI using a new holographic method

This paper discusses a method in which a wave source is visualized by electromagnetic wave holography by scanning the receiver antenna on a plane. The method presented in this paper does not use the Fresnel approximation or the Fraunhofer approximation, and there is no constraint on the distance between the measuring plane and the object of observation. By partitioning the object of observation, the method can be applied, even if the object of observation is larger than the hologram measuring plane. The two-dimensional fast Fourier transform is introduced to each of the partitioned planes, so that the speed of the numerical integration is improved. To improve the accuracy of the intensity of the reconstructed image, the directivity of the receiving antenna is considered. For observation of the leaked electromagnetic wave in a real system, a hologram observation system is proposed in which some variation of the observation frequency can be tolerated. Using the proposed observation system, the radiation from a dipole antenna is observed, and a computer simulation is performed. These results show that the resolution is improved and that a wider range of observation is realized than in the conventional method. Lastly, as an application example, the leaked electromagnetic waves from a metal cabinet are observed on a 57 cm × 57 cm plane at a distance of 200 cm, and a visualized result for 285 cm × 285 cm is presented.