Modular design of dual-mode filters using elliptic cavities

The paper presents a new design of dual-mode filters by using elliptic cavities in waveguide technology. The cavities are homogeneous and contain no coupling elements. Such a design is very suitable for high power applications. The design is based on coupling schemes in which the resonant frequencies of the resonators affect directly the performance of the filter. These parameters are easily adjusted in an elliptic cavity by controlling its major and minor axes. Each cavity can generate and control up to one transmission zero at a finite frequency. For applications requiring a reduced sensitivity to manufacturing errors, the dual-mode cavities are separated by quarter wave sections. An all-pole response can also be designed by suppressing the transmission zero of each cavity. Example filters are designed to demonstrate the validity of the approach.