Dual-Band SIW Filter With Widely Separated Passbands Based on TE101 and TE301 Modes

Abstract

In this paper, a novel dual-band substrate integrated waveguide (SIW) filter with widely separated passbands is presented, which is realized by dual-mode TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</inf> and TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">301</inf> resonances. To make the TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">301</inf> mode create the second passband, two novel techniques to suppress the TE201 mode are proposed and discussed. The proposed techniques excite the TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">201</inf> mode but either block its coupling path or cancel its effect at the output port, which can be identified as mode blocking and mode cancelling, respectively. They show a merit of introducing an extra transmission zero, which is beneficial to enhance the out-of-band rejection. To verify the concept, a dual-band filter prototype operating at 6.5 and 11 GHz is designed and fabricated, which shows a good electrical performance and a compact size.