Need information about Parallel Plate Mode

Hallo,

on PCB boards normally ground vias are placed to ensure low impedance return current pathes and to kill the parallel plate mode, which occurs between two opposite metal layers.

This PPM mode seems to be unequal to the TE mode in hollow waveguides,
because the TE cutoff frequency is much too high for common distances between
the metal planes. In my case the distance is only 50 um.

Has anybody more information about the parallel plate mode.
Is there a similarity to TE modes ?


greets
elektr0

The parallel plate mode is a TEM mode (meaning no cutoff), not a TE mode, and is quite different from the TE mode in a rectangular waveguide. The sidewalls short the potential at the sides, and thereby short the TEM (parallel plate mode). I would guess a better approximation is to make the sidewalls of the rectangular waveguide perfect magnetic conductors instead of PEC's. (I have not gone through the math; hence, this is only an educated guess.)

Can you be more specific on what you want to know about the PPM? This is a basic transmission line, and most textbooks would have a description. The two microwave books on my shelf, Pozar's and Collin's, both have an analysis of this waveguide.

@Wiley.

Ok. Independently from the distance of the ground planes, there will be
PPM propagation. Whereas TE mode arises only at lambda/2 plane distance.
I will scan Pozar and Collin first, and then ask further questions. OK

you can download fundation engineering microwave by collin from link:
https://www.edaboard.com/viewtopic.php?t=97588