In this paper, half-mode substrate integrated waveguide (HMSIW) bandpass filters with modified complementary split-ring resonators (CSRRs) for the reduction of machining tolerance sensitivity are presented. Profiting from the evanescent-mode resonance operation, the conventional CSRR and its modified versions have been successfully utilized to miniaturize the physical sizes of SIW components. However, few investigations have focused on the fabrication tolerance. Performance of most CSRR-loaded SIW components, as well as their modified versions, is significantly sensitive to the fabrication tolerance. Hence, as the conventional machining process is with large fabrication tolerance, the CSRR-loaded SIW components suffer from limited performance and restrained application practicability. To decrease the influence from the machining tolerance on the components' performance, the slots-embedded CSRR (SECSRR) is proposed and loaded into HMSIW to design evanescent-mode filters. Numerical simulations exhibit that the proposed SECSRR can help to decrease the machining tolerance sensitivity effectively as the fractional frequency offset resulting from the fabrication error is reduced from ±8.11% to ±4.95%, which indicates that the proposed SECSRR is able to improve the suitability of SIW/HMSIW components and circuits for practical radio frequency (RF) and microwave applications.
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