Power ratio
Impedance matching
consider a system of two parallel interfaces, from left to right the medium impedances are respectively , and . The distance between the two interfaces to be
-
by the continuity equations of the displacement and velocity at the two interfaces, we conclude the total reflective coefficient of the double layer system to be
we define the effective impedance to be , thus acquiring a similar reflective coefficient as for a single interface system with and
Quarter wave matching (i.e. the interface spacing with impedance has length )
- Satisfied under the condition ,
- this gives the zero reflection condition for quarter wave matching