In this paper, a compact wideband bandpass filter is proposed using a stepped impedance stubs resonator and substrate integrated coaxial line (SICL) technology. The resonator produces three resonant frequencies and two attenuation poles near the edges of the passband, so a wide bandwidth and a high frequency selectivity transmission characteristic can be obtained. Employing multilayer printed circuit board (PCB) process, a filter prototype with compact size of 0.1 λ0×0.09 λ0 is fabricated. The measured results indicate that the proposed filter has a central frequency of 12.98 GHz with 28.1% fractional bandwidth, an insertion loss of 1.3 dB, and a wide stopband up to 28.5 GHz with a rejection better than 25 dB.
