Compact Monolithic SLM 3D-Printed Filters using Pole-Generating Resonant Irises

This paper proposes a new pole-generating resonant iris structure for the design of iris-coupled cavity filters. By replacing the conventional reactive iris with a resonant iris, extra transmission pole can be generated without increasing the number of resonant cavities. This leads to several design advantages: (i) a more compact filter structure; and (ii) ability to realize wide bandwidth and to improve out-of-band rejection. To demonstrate these, a third-order Chebyshev filter is designed and implemented, occupying the same footprint as a second-order filter. To facilitate the formation of the intricate resonant iris structures, the filter was printed monolithically using selective laser melting (SLM) technique. Very good agreement between the measurements and simulations has been achieved.