The lumped resonant elements in waveguides

Traditionally waveguide filters are constructed using a limited amount of resonant elements. The volumetric cascade resonators or resonant diaphragms are applied as passing circuits. Rejection circuits are usually implemented as series stubs. The expansion of the nomenclature of resonant elements allows us to reduce considerably the dimensions of devices and to improve their electrical parameters. In this paper we consider resonant elements having a small longitudinal (along the waveguide) dimension that allows us in most cases to consider them as lumped