I'm educating myself and need some assistance understanding the absolute
basics of the impedance formula for E'r (relative permittivity).
Below is the basic formula for Zo in embedded stripline
 
                              87              [5.98H]
                          -----------  *  LN -------------
                   sqrt E'r+1.41       [ 0.8W+T ]
 
where
 
E'r = Er(1-e(-1.55H1')
                 --------------
                     H
Er = material defined relative permittivity
H = the distance from the reference plane to the signal line
H' = the distance from the reference plane to the top of the dielectric
 
My question: what does the variable e represent in the calculation for
E'r?
 
 	
Sue Reade
CAD Engineer
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