Myths in microwave filter theory

In the microwave filter theory there are several concepts and ideas that can be considered as misleading or even false. In the paper some of the “mythical” concepts are addressed and explained. Coupling between resonators realized through ideal inverters is analyzed by means of eigenfrequency method and differences between inverters and their impact on coupling matrices are presented. The lossy ideal inverters are analyzed and it is shown that they are not passive. Coupled transmission lines are analyzed by means of coupled mode theory and non-physical properties of the traditional circuit model are shown.

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