Yuichiro Murata

3D-FEM analysis for shielding effects of a metallic enclosure with apertures

The leakage of electromagnetic (EM) waves from a metallic enclosure with apertures, from a metallic mesh and from a metallic shield thinner than the skin depth are numerically analyzed using a three dimensional finite element method (3D-FEM). The calculated results were compared with measured results using a simple shape model enclosure with a generator inside. The phenomena predicted by the numerical analysis agree with the measurement results.

Near and far fields analysis from flat cables

The electromagnetic radiation from flat cables (flexible printed circuit:FPC) which have different structures are analyzed using a three dimensional finite element method (3D-FEM). The electric fields at 3 m from the FPC were calculated by an integration method using the calculated E and H values inside of the FEM region and Greens function. The calculated radiation from a microstrip structure FPC is smaller than that from a single layer FPC by about 17 dB in near field, 25 dB at 3 m from the FPC. The results were compared with E fields measured by antenna at 3 m from the FPC. The measured difference between the microstrip FPC and the single layer FPC is 11.5 dB. Adopting a microstrip structure FPC is effective in drastically reducing the EMI noise from the cable.

Analysis of Parasitic Couplings in EMI Filters and Coupling Reduction Methods

In this paper, the effects of parasitic couplings in electromagnetic interference (EMI) filters are investigated using an equivalent circuit analysis and experiments. The investigated filter has the C-L-C filter structure which is composed of foil capacitors, feedthrough capacitors, and a toroidal inductor. The parasitic couplings between input capacitors and output capacitors increase the transfer function of the filter. We found that the increase of the transfer function is caused by two kinds of parasitic couplings: one is the parasitic inductive coupling between the two resonance circuits which are composed of feedthrough capacitors and foil capacitors, and another is the parasitic capacitive coupling between the input and the output foil capacitors. Balancing the two parasitic couplings, it is possible to reduce the transfer function increase without increasing the filter size. The experimental results of transfer functions agree with the equivalent circuit analysis results up to 30 MHz. The balancing condition obtained by the circuit analysis has been confirmed by the experiments.

Noise immunity design for multilayer printed circuit boards using electromagnetic simulation

We report on electromagnetic noise immunity design for multilayer printed circuit boards using quasi three dimensional electromagnetic simulation, and its application to products. For evaluation of the electromagnetic simulation, a prototype multilayer printed circuit board was designed and tested. The coupling of its power circuit patterns on the same layer and the coupling of ground patterns on the different layers, which are thought to be fundamentally impossible to analyze with quasi three dimensional electromagnetic simulation, were measured and simulated. The measurement results of the peak level of the coupling between the patterns agree with the simulation within 10%. We confirmed that quasi three dimensional electromagnetic simulation was applicable to noise immunity design if the following conditions are satisfied: the same ground pattern was placed under the power patterns, or FG and the SG were explicitly connected with capacitors, those conditions are usually satisfied in printed circuit boards.

Susceptibility of notebook computers to HPM

In this paper, we evaluate the susceptibility of notebook computers to high power microwave (HPM) pulses. We have developed a HPM test instrument with stripline structure. The structures of the test instrument are investigated through finite-difference time domain (FDTD) analysis to get homogeneous electromagnetic fields inside the instrument. The developed instrument can apply a 2.7 kV/m electric field below 3 GHz with using a 100 W power amplifier. The stripline instrument is an open structure, which can easily apply electric fields to a specific part of notebook computers. The HPM pulses were applied to the main body of notebook computers. We obtained the frequencies of the HPM pulses at which the notebook computer operation has failed. Radiated susceptibility tests were also carried out on notebook computers with an antenna. The computer failure frequencies of the test instrument agree with the failure frequencies from observed during the radiated susceptibility test. Our test instrument is useful for preliminary test of notebook computers and for investigating the effective HPM pulse condition.

Finite Element Software For Practical EMIProblems

MAGNA/EMI is a finite element code based on the coupled A 0 method for three-dimensional electromagnetic (EM) field analysis. The paper describes this four-component vector/scalar potential formulation in some detail. It explains how to choose the gauge condition for each application model and how to set the electric and magnetic field directions on the boundary surfaces. The perfectly matched layer (PML) concept is used as the absorbing boundary condition (ABC). The accuracy of results is confirmed by comparison with analytical solutions for the voltage standing wave ratio (VSWR) and skin depth computation. Computed and analytical values agree well even when the finite element aspect ratio is less than optimal. Both incomplete Cholesky conjugate gradient (ICCG) and Gauss-type equation solvers are available with MAGNA/EMI. A comparison of the solvers is made for both geometrical and electrical bad aspect ratio problems. Two practical applications, cellular phone shield-design and electromagnetic resonance inside a car, are presented as examples. They demonstrate that MAGNA/EMI is a valuable tool in the hands of EMI/EMC engineers.