Compact Half-Mode SIW Filter With High Selectivity and Improved Stopband Performance
Lin Gu, Yuandan Dong
Abstract
In this letter, a novel filter with high selectivity is proposed using a hybrid multilayer half-mode substrate-integrated waveguide (HMSIW). First, a rectangular HMSIW is used to realize a third-order cross-coupling topology, which could introduce a transmission zero (TZ) on the left side of the passband. Then a ring microstrip resonator is added to form the new dangling block, which realizes the fourth-order response with an additional TZ located on the right side of the passband. Sharp skirt and high selectivity are then achieved. In addition, since each mode of the HMSIW has different external coupling strengths at the same feeding position, harmonic suppression can be achieved easily by moving the feeding position. Therefore, a good stopband can be obtained with decent out-of-band performance. Size reduction is also achieved through the multilayer HMSIW and hybrid microstrip structures as well.