I am running a structure with two mesh planes and a signal line inside, and PropCalc does not seem to be doing what I thought. What could be wrong?
If the structure contains N non-touching conductors, then, for a quasi-TEM analysis, there will be N-1 modes; so the above structure supports two modes. In most cases, the user intends for the two mesh reference planes to be shorted together so that only one mode is supported — thus, the user needs to add a thin conductor (located at some position that will minimally affect the field near the signal line) in order to short the two mesh planes together and preclude the additional mode. The original solution is correct, however, and would be appropriate if the two mesh planes were not shorted (for example, in a delta-I analysis where the voltage difference between mesh planes is sort).
