Design and realization of 10th order (10-4-4) self equalized dual mode waveguide channel filter

This paper presents the synthesis and realization of 10th order (10-4-4) self equalized dual mode waveguide channel filter in C-band. The filter is realized with circular cavities in TE111 mode for optimum size and very high unloaded quality factor. The filter is designed in dual mode configuration; where one physical cavity represents two electrical resonators; so 10th order filter is realized with five physical resonant cavities. The equivalent linear frequency drift (for temperate variations) is incorporated at the synthesis stage of the filter. The engineering model of the filter is manufactured using aluminum metal. The filter is synthesized using indigenously developed software tool. Eight finite transmission zeros are incorporated; four transmission zeros are for out of band rejection and a complex quad of transmission zeros is for group delay equalization. The filter is realized with quasi Pfitzenmaier topology having better input/output isolation and meeting unusual layout restrictions. A full wave model of the filter is simulated in software tool and an efficient method for finding approximate lengths of tuning screws is proposed. This method can be utilized in computer aided tuning (CAT) of waveguide filters. The results of the manufactured engineering model of the filter show good agreement with the theoretical/simulation results.