APPENDIX G
Multilayer Thin-Film Filters
TO UNDERSTAND THE PRINCIPLE of operation of dielectric thin-film multicavity filters (DTMF), we need to digress and discuss some results from electromagnetic theory.
G.1 Wave Propagation at Dielectric Interfaces
A plane electromagnetic wave is one whose electric and magnetic fields vary only in the spatial coordinate along the direction of propagation. In other words, along any plane perpendicular to the direction of propagation, the electric and magnetic fields are constant. The ratio of the amplitude of the electric field to that of the magnetic field at any such plane is called the impedance at that plane. In a medium that supports only one propagating wave (so there is no reflected wave), this impedance ...
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