TE₁₀₁ Substrate Integrated Waveguide Filter with Wide Stopband Up to TE_10(2n-l) and Coplanar Ports

This article presents a new method for substrate integrated waveguide (SIW) filters to achieve wide stopbands. Using the proposed staggered inter-coupling structures, double-layer SIW filters working at the fundamental mode TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</inf>(f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>) can have wide stopbands up to TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10(2n-1)</inf>, where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex> is the order of the filter. They can break the upper limit of the stopband extension and have coplanar ports suitable for planar circuits and systems in comparison to their multilayer counterparts, and they can further extend the stopbands and have shielding structures suitable for high-performance and high-frequency applications compared to their hybrid counterparts. Three examples are provided. The measured results show that they respectively achieve wide stopbands up to 3.97f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>, 5.22f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>, and 6.53f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>. The proposed technique should be effective for developing wide stopband SIW filters for microwave circuits and systems.