An Improved Compact Substrate Integrated Waveguide (SIW) Bandpass Filter with Sharp Rejection and Wide Upper-Stopband

An improved compact substrate integrated waveguide (SIW) bandpass filter based on quarter-mode substrate integrated waveguide (QMSIW) is proposed in this paper. QMSIW bandpass filter has good performance and many advantages such as compact size, low insertion loss and easy integration, but narrow upper-stopband and bad rejection skirt still need to be improved. Source-loaded coupling structure can produce a pair of transmission zeros to sharpen the rejection skirt, and the upper-stopband can be further improved by utilizing lowpass filter. By using above methods, an improved filter has been designed and simulated, the simulated result shows that the filter has sharp rejection skirt and wide upper-stopband.