Design of THz Dual-Band Bandpass Filter Using Quarter-Mode SIW Resonators

In this paper, a terahertz (THz) dual-band bandpass filter is proposed using quarter-mode substrate integrated waveguide (SIW) resonators. The quarter-mode SIW resonator in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$130-\text{nm} \text{SiGe}$</tex> technology is analyzed, showing a relatively high <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex> factor as compared to the conventional microstrip and lumped-element LC components. A two-path dual-band filter topology is used, where the operating frequencies and bandwidths of the passbands can be controlled separately. A transmission zero is generated between the two passbands, enhancing the isolation between two passbands. For verification, the dual-band filter chip operating at 145 GHz and 255 GHz is designed with a chip area of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.55 \times 0.44 ~\text{mm} 2$</tex> on the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$130-\text{nm}$</tex> SiGe technology. The insertion loss at the two passbands are 2.95 dB and 2.29 dB.