Doublet Modular for Design of Microwave Filters

A novel doublet modular in filter design is introduced in the paper. We can use the doublet modular in bandpass filters. Using the doublet modular, asymmetry transmission zeros are created in the bandpass filter. We can locate the two transmission zeros at one side of the passband or both side of the passband. The doublet modular is demonstrated very flexible by showing a number of coupling matrices of cases. It is earlier to design higher order filters of high performance by cascading such doublet modular. And the response of the filter will be improved. In this paper, zero-shifting properties of the filter with source and load coupling are also proposed, which is different from zero-shifting properties proposed in filters without source and load coupling.