Substrate Integrated Waveguide L-Shaped Iris for Realization of Transmission Zero and Evanescent-Mode Pole

This paper investigates L-shaped iris (LSI) embedded in substrate integrated waveguide (SIW) structures. A lumped element equivalent circuit is utilized to thoroughly discuss the iris behavior in a wide frequency band. This structure has one more degree of freedom and design parameter compared with the conventional iris structures; therefore, it enables design flexibility with enhanced performance. The LSI is utilized to realize a two-pole evanescent-mode filter with an enhanced stopband and a dual-band filter combining evanescent and ordinary modes excitation. Moreover, a prescribed filtering function is demonstrated using the lumped element analysis not only including evanescent-mode pole, but also close-in transmission zero. The proposed LSI promises to substitute the conventional posts in (SIW) filter design.