Design of dual-band filter using SIW resonators with open circuits on opposite sides

In this paper, a novel dual-band filter using SIW resonators with open circuits on opposite sides is proposed. Inner coupling is realized by the coupling slot and metal-hole rows. External coupling is achieved by the dual-feeding line, simultaneously exciting the desired modes (TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">100</inf>and TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">102</inf>). Through the technology of slot perturbation, a closely-space dual-band (4.85/5.45 GHz) filter is achieved with a 3 dB fractional bandwidth (FBW) of 3.8% and 3.9%, respectively. The dual bands achieve a low insertion loss of 2.4 dB and 2.3 dB, respectively, along with return losses better than 15 dB. The adjacent passband isolation exceeds 20 dB, and stopband high rejection is achieved by introducing six transmission zeros. The measured results are consistent with the simulated ones.