Novel FDTD simulation method using multiple-analysis-space for electromagnetic far field

Wide-band undesired electromagnetic noise near electronic systems, which includes small noise source like the printed circuit board (PCB), is a current problem in the field of electromagnetic interference. However, the estimation method for the electromagnetic noise near a system under test has not been established. This paper proposes a newly developed estimation method of the electromagnetic noise for a wide area, from near to far field, using the finite difference time-domain (FDTD) method. The proposed FDTD simulation method is an estimation technique for near to far field with multiple analysis spaces (MAS). The MAS has an internal analysis space (IAS) and an external analysis space (EAS). The analysis near a radiation source can be calculated in the IAS. The EAS is the outside space from IAS, which is for calculation of the far field. It is expected that the proposed FDTD method by MAS (FDTD-MAS) decrease in the calculation cost in terms of computational time and memory costs, especially for estimation of radiation from PCB. The principle procedure of the FDTD-MAS method is described in the first part of this paper. As example of advantages of the calculation and confirmation of the calculation accuracy, the electric field distributions radiated from a 1-GHz half-wavelength dipole antenna in an IAS of 0.3×0.3 m² area and an EAS of 7×7 m² area are used as examples. When the cell size ratio of IAS to EAS is changed from 6 to 20, the FDTD and theoretical values show good agreement. It is indicated that the FDTD-MAS simulation method is one of the most powerful tools for the estimation of electromagnetic noise from near field to far field from small and thin source.