Computation of EMC Properties of Slots and Printed Circuit Boards

Doktorsavhandling, 1998

This thesis deals with the numerical solution of electromagnetic compatibility (EMC) problems for electronic systems, such as radiated emission, susceptibility and crosstalk on printed circuit boards and transmission through slots. The analysis of printed circuit boards is done by using an electric field integral equation (EFIE) expressed in the frequency domain, which is solved by using the method of moments. In order to incorporate the dielectric substrate of the circuit board a spectral domain formulation is used which makes use of a physical asymptotic solution to speed up convergence. The theory has been implemented in a user-friendly computer code which has been extensively tested against previously published results and against results obtained by other methods and programs. The crosstalk on printed circuit boards is also studied in a different way by using multi-conductor transmission line (MTL) theory. In order to use this formulation the per unit length parameters of the MTL have to be known. These parameters are computed by a developed finite difference program. The parameters are then used for modelling the MTL as lumped circuit element sections by means of the circuit program SPICE. They are also used directly in a separately developed computer program based on the finite difference time domain technique (FDTD). This FDTD program solves the transmission line equations in the time domain and the crosstalk can be obtained either in the time domain or in the frequency domain through a FFT (fast fourier transform) routine. The induced currents due to incident electromagnetic fields and transmission line networks can also be calculated by the program. The transmission of electromagnetic fields through slots is also considered. It is shown that by using the concept of soft and hard surfaces methods for reducing the transmission can be understood. The analysis of slots with corrugations or chokes is done by using an integral equation approach which is solved by the method of moments. Results for different corrugated slots are presented and compared with results from measurements.