Design of planar narrow band millimetre-wave filter with wide stop-band

This paper presents a planar millimetre-wave (mmwave) band pass filter based on substrate integrated waveguide (SIW) and substrate integrated coaxial line (SICL) techniques. Four half wavelength mircrostrip resonators are imbedded in the SIW cavity to improve Q-factor. Due to the closed configuration which eliminates radiation loss, the filter presents a relatively low insertion loss. The proposed filter has a 3dB fractional bandwidth of 1.6% across frequencies from 29.8GHz to 30.3 GHz and 20dB rejection band from 30.7GHz to 58 GHz.