Characteristics of Near-Field to Near-Field and Near-Field to Far-Field Transformation for Wideband Radiation Source Antenna in FDTD Method

Electromagnetic interference (EMI) tests are widely performed to confirm immunity of in-vehicle equipment. In this test, several frequencies of EM waves are exposed to the in-vehicle equipment. For this reason, wideband antennas are used. It is important to accurately understand the electric field distribution radiated from the antenna. However, calculating the electric field distribution using FDTD method requires significant computation time. To reduce computation time, near-field to near-field and near-field to far-field transformations are useful techniques, but their characteristics for wideband antennas have not been clarified. In this study, we compared the electric field distributions obtained by these transformations with those calculated directly by expanding the analysis domain. As a result, we clarified the characteristics of near-field to near-field and near-field to far-field transformations in FDTD method.