Effect of layered media on the parallel plate impedance of printed circuit boards

This paper evaluates the impact of layered media on the parallel plate impedance of printed circuit boards. In the parallel plate impedance computation using the radial waveguide method (RWM) for infinite planes and a contour integral method (CIM) for finite planes, the layered nature of investigated structures can be accounted for by effective wave numbers. Here, the effective wave numbers are obtained using either an exact solution from the transverse resonance method (TRM) or adopting approximations based on the assumption of quasi-TEM fields and the applicability of suitable averages. The wave numbers obtained with these techniques are compared for typical structures of interest, and the parallel plate impedance computed with effective wave numbers is evaluated and compared to a full wave solution. The results show that a comparatively simple approximation for the effective wave number is sufficient for an accurate parallel plate impedance calculation.