In this study, the frequency and spatial properties of undesired electromagnetic radiation distribution around a simple printed circuit board (PCB) model, which only has the mismatching printed line (PL) and ground, are estimated. Finite difference time domain (FDTD) modeling is developed for the analysis space, which is 500 400 51 mm3 in size, around the PCB. As the driving clock pulse has a very wide frequency bandwidth, ranging from kHz to GHz, basic and precise investigation of the noise emission mechanism from the basic model is performed. The results of the magnetic field Hx on the PCB as determined by FDTD simulation, and those of the experiment, driven by a clock pulse, agree well. The results show that although this approach is basic and simple, it becomes clear that the frequency and spatial characteristics of the electric and magnetic field near the PCB are influenced by the wavelength of the frequency and appling the driving clock pulse, and the low-frequency component of the electromagnetic distribution around the PCB is larger than the high-frequency components. It is suggested that the low-frequency noise problem should be carefully considered.

To clarify the transmission characteristics and near magnetic field on the angle pattern for the parallel transmission lines, the authors investigate how influence the angled pattern on the transmission lines by experiment and calculation. The angled patterns on the transmission lines are straight, right angle and curve. It shows that the suppression of EMI radiation at the angled pattern on the parallel transmission lines of the magnetic head is essential. In addition, it is suggested that angle pattern might be one of cause for the signal distortion and specific EMI radiation at high frequency.

As the basic study of the electromagnetic interference (EMI) problem at the circuit elements, the near magnetic field distributions above resistors for the termination of a transmission line are measured to reveal the profile of radiation. Five kinds of resistors and two types of resistance values are sampled. The results showed that the variation of the near magnetic field distribution above the transmission line is effected largely by the reactance of the resistor at the high frequency. These results are the basis for the design of the structure of the component.

The effect of the structure with difference on cross-section for the enlarged models that simulates signal transmission line (STL) in the magnetic head of HDD is discussed. The experimental results suggested that strip and shield structure are effective for suppression of EMI.

The spatial distribution of the electric field in the low to high frequency bands radiated from printed circuit board (PCB) should be estimated continuously from near to far field. The characteristic of the electric field distribution is analyzed by the FDTD-multiple analysis space (FDTD-MAS) method, which can analyze from near to far field continuously, and compared with measured results. Since the analyzed electric field distribution is good agreement with measured results, it is suggested that the continuous distribution for electric field from near to far field can be calculated by the FDTD-MAS method. The electric field at low frequency is larger than that at high frequency within 1 m.

This study is to clear how the impedance and the current of a simple printed line model involve to the near field electromagnetic noise radiation, by computer simulation and experiment. Frequency characteristics of the impedance and the current of the printed line and the near field noise are considered, from low to high frequency components. The model size 225 60 0.51 mm3, length of the line is 185 5 mm2 and 1 kΩ termination resistance is connected as non-matching load. FDTD method is used to calculate the impedance, the current waveform and the near field noise. Measurements of the line impedance and the near field noise spectrum by clock pulse are compared with simulations. It is cleared that using FDTD method, the characteristic of impedance of the printed line model, the current waveform, and the near field noise can be calculated at the same simulator. As results, from calculation and measurement, the near field noise has a relationship with impedance of printed line model. Emission at frequency less than 200 MHz, which is near the wavelength of λ/4, is observed at significant intensity. So, it is suggested that near field noise emission should be discussed from low to high frequency and analysis of the characteristics of the printed line and magnetic near field noise using FDTD method and measurement is useful to basic examination of complex PCB models.

To estimate the electromagnetic noise radiated from a printed circuit board (PCB) driven by a switching device, the finite difference time domain (FDTD) simulation method implementing the switching transistor is developed. The electric and magnetic field distributions on the signal line driven by a switching transistor are calculated or measured. These calculated and measured results show good agreement. The electric and magnetic field noises at typical impedance conditions modeled for the switching condition, i.e., the ON or OFF state of the transistor, are estimated by the FDTD calculation. The variation of the radiation noise when the switching transistor is turned ON or OFF is large at 216 MHz, whose input impedance of the signal line is small. It is speculated that the noise radiation at the 10 Ω signal source impedance condition that is modeled for the ON condition shows good agreement with the noise distributions at the driving condition.