Realisation of controllable transmission zeros by perturbation technique for designing dual-mode filter using substrate integrated hexagonal cavity

Novel designs of dual-mode substrate integrated hexagonal cavity (SIHC) bandpass filters are proposed in this study. Different filters responses in terms of switching transmission zeros are realised using perturbation technique. With the variation of perturbed length, the change of modal resonant characteristics and field patterns of the degenerate modes are also studied. Two pole and four pole filters with transmission zeros are designed and fabricated. All the theoretical analysis with the help of coupling matrix are verified with experimental results, showing good agreement between them.