Highly Selective Substrate Integrated Waveguide (SIW) Dual-band Band Pass Filter

In this paper, a dual-band multilayer trisection BPF is designed. The proposed BPF offers 48 dB of rejection at the (f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf>+f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>)/2 where f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> = 2.45 GHz and f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> = 3.5 GHz are the mid band frequencies of the two passbands. With Fractional Bandwidths (FBW) of 4% and 5% respectively, the BPF covers entire 2.45 GHz (ISM application) and 3.5 GHz (Targeted 5G communication bands application). The fundamental TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</inf> and second higher order TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">210</inf> modes of rectangular SIW resonators are utilized to create the two above mentioned passbands, respectively. The trisection topology used to implement the BPF, offer three Transmission Zeros (TZ) and an additional TZ due to higher-lower order mode coupling. These three TZs significantly improve the out of band rejection rate. The simulated Return Loss (RL) and Insertion Loss (IL) are better than 19 dB and 1.8 dB for the first fundamental pass-band, whereas in second pass-band this is better than 18.5 dB and 2 dB, respectively. Due to the additional TZ created by the higher-lower order mode coupling, the stopband rejection reaches to 62 dB at (f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>+0.3) GHz.