Modular Design of a Fourth-Order Waveguide Bandpass Filter With High Selectivity

In this paper, a novel fourth-order waveguide bandpass filter (BPF) with two stacked layers is presented. Compared with the traditional ladder filter, a modular design method is proposed by decomposing the fourth-order filter into two second-order sub-filters, which are separately realized by cascading two waveguide resonators in the two stacked layers. Thus, the complexity in tuning process of filter could be greatly reduced. In addition, two transmission zeros (TZs) could be generated at both sides of the passband, thus achieving high selectivity of the filter. The simulation results show that the proposed method is feasible.