Determination of Equivalent Coupling Surface of Passive Components Using the TEM Cell

The design of cheaper and more compact electromagnetic compatibility (EMC) filters can be achieved by exploiting the magnetic coupling between components. This requires the knowledge of coupling coefficients between components and, consequently, of their equivalent coupling surface. The aim of this paper is to present how this coupling surface can be determined using a transverse electromagnetic mode cell. This methodology is described and applied to two different cases: a capacitor and an inductor. In order to validate the determination and usage of equivalent coupling surfaces, a comparison between the calculation and measurement of mutual inductances is carried out on practical examples.

I. Introduction

In Filter design, intercomponent coupling plays a major role in the filter response. It was demonstrated in [1] and [2] that the magnetic coupling between the components has to be taken into account to have a good prediction of the filter attenuation. Furthermore, in [3], it was shown that the filter attenuation highly depends on the position of the components and, therefore, on the magnetic coupling between the components. For the purpose of calculating the coupling coefficient, the principle presented in [4] is used.