Fundamentals of a new class of magnetically tunable waveguide filters

In this work a class of magnetically tunable filters based on a new principle is studied. These filters exploit the selective properties of a rectangular waveguide containing a thin magnetized ferrite slab lying against one sidewall. The reflection loss of the filter in the stop bands is not due to resonators, but is produced by reflection from the mentioned structure when brought below cutoff. We discuss, in general, how the geometry and the magnetic parameters affect the behavior of this class of filters. Then we study the characteristics of the high-pass type filters and give a procedure for their design. The high-pass filter constructed showed a behavior in good agreement with our theory.