Re: [SI-LIST] : Propagation velocity / discontinuous reference pl ane

Chris Cheng (
Wed, 06 May 1998 19:36:39 -0700

The effect of a highly meshed reference plane depands on
the mesh hole dimension vs. the signal trace. if the hole
size is significantly larger then the trace width, the
signal will be propagating in a non TEM mode. This is
indepent of whether the hole itself is larger or small compared
with the wavelength of frequence of interest. The net
result will be :
i) there will be forward crosstalk even through you
have homogeneous media
ii) the impedance will be way off from calculation
based on solid plane approx
iii) ditto on crosstalk calculation
the main reason is due to the image current has to
flow around the hole and thus increase the loop
inductance and forcing image current of many traces to
overlap each other (i.e. crosstalk)

chris cheng

p.s. i don't speak for my company or any product it develops