` (UTC)  I suspect there is some confusion between the power S11 parameter and the voltage s11 parameter.  I rederived the whole thing.  If rho is the voltage transmission coefficient, then the scaled reflected power goes as rho^2, and the scaled transmitted power goes as (1-rho^2).  This would be if a short square-wave pulse for instance impacts the discontinuity.  See  ``Advanced Engineering Electromagnetics``, by Copnstantine A. Balanis p. 182 , where the field derivation is made (which assumes continuity of the E field, like voltage, and H-field, like current at the boundary)   12:18, 15 March 2011`