Double-folded substrate integrated waveguide band-pass filter with transmission zeros in LTCC

Abstract

A miniaturized substrate integrated waveguide (SIW) band-pass filter with two transmission zeros is proposed in low-temperature co-fired ceramic (LTCC) technology. The miniaturization of the filter is achieved by vertically stacking three double-folded SIW resonators. To strengthen the coupling between the feeding structure and the resonators, a new meandered microstrip feeding line is introduced. In addition, to realize better out-of-band rejection performance, two short-circuited lines are adopted in the filter design to achieve two transmission zeros outside the passband. To verify the design concept, an X-band LTCC band-pass filter was designed, fabricated, and measured. Both simulation and measurement results indicate that the proposed filter has good frequency response, high selectivity, and a size reduction of about 87% in comparison with conventional planar direct-coupled waveguide filter.

Acknowledgments

This work was supported by the National Natural Science Foundation of China under Grant No. 61101047 and the Specialized Research Fund for the Doctoral Program by the Ministry of Education of China under Grant No. 20113219120015.