Size-reduced bandpass filters using quarter-mode substrate integrated waveguide loaded with different defected ground structure patterns

In this paper, three different defected ground structure (DGS) patterns are proposed and loaded into quarter-mode substrate integrated waveguide (QMSIW) to implement three size-reduced bandpass filters. Using QMSIW can achieve a size reduction nearly 75% with respect to its substrate integrated waveguide (SIW) counterpart. Furthermore, the utilization of DGS can further reduce size over 40% compared with its corresponding conventional QMSIW circuits. Measured results of these filters are in good agreement with the simulated ones, with size reductions, compared with some reported QMSIW filters, about 26%, 34% and 42%, respectively.