  We have developed the mode matching technique that is based on the using the
eigenmodes of circular cavities and the eigenwaves of circular waveguides as
the basic functions for calculation the properties of nonuniform disc-loaded
waveguides. We have obtained exact infinite systems of coupled equations which
can be reduced by making some assumptions. Under such procedure we can receive
more exact parameters of nonuniform equivalent circuits by solving the
appropriative algebraic systems. These parameters of equivalent circuits are
functions both geometric sizes and frequency. Moreover, under such approach all
used values have interpretation. We called this approach as coupled cavity
model.
