Design of Compact Bandpass Filter With Enhanced Frequency Selectivity Based on EMSIW Cavities

A compact bandpass filter with enhanced frequency selectivity is proposed in this paper. The circuit size is reduced by utilizing eighth-mode substrate integrated waveguide (EMSIW) resonators. Both electric coupling and magnetic coupling are employed within the four employed EMSIW resonant cavities, for the purpose of generating one pair of transmission zeros (TZs). Moreover, an additional source-to-load coupling path is constructed, to introduce another pair of TZs which leads to further improvement of frequency selectivity. A filter prototype is simulated, fabricated, and measured. Good agreement is obtained between simulated and measured results.