Compact triple-mode HMSIW balanced passband filter with intrinsic common-mode suppression

In this article, a compact triple-mode balanced passband filter with intrinsic common-mode (CM) suppression is designed by using a single isosceles right triangle perturbed half-mode substrate integrated waveguide (HMSIW) cavity. The perturbation metallic vias are introduced to tune the first three resonant modes of HMSIW cavity to form a passband. Furthermore, the planar differential microstrip-pin feed structure is designed to excite the perturbed substrate integrated waveguide cavity. Under CM operation, when the substrate's height is less than lambda(g)/4, the space between perfect electric conductor and perfect magnetic conductor cannot transmit electromagnetic wave, so CM noise can effectively cut off at the planar differential feed structure in a wide frequency range. Finally, a prototyped prototype at 4.5 GHz is designed and fabricated, and measured results show good agreement with simulated ones.