Design & realization of direct coupled Ku-band waveguide iris filter using coupling matrix model

This paper describes the design and realization of 7th order Ku-band bandpass filter. This filter is a part of pre-filter required for desired frequency spectrum selection in a communication satellite. The filter is realized with rectangular waveguide WR75 in TE₁₀₁ mode; because it can give optimum size with high unloaded quality factor and wide spurious free window. The engineering model of the filter is realized with Aluminum material. Temperature variations cause the volumetric thermal expansion of the filter and the equivalent linear frequency drift is incorporated at the synthesis stage of the filter. Tolerance analysis of the filter is also performed to compensate the manufacturing errors. Semi-miniaturized SMA to waveguide transformers were also developed for testing of the filter. Filter is synthesized using indigenously developed software tool. Utilizing the coupling matrix; each inter-resonator coupling iris and input/output iris is designed separately. There is a good overlap of the tested and the simulated responses.