High selective SIW bandpass filter with flexible bandwidth and transmission zero for 5G application

This paper presents a novel design of an electric coupling structure for a substrate-integrated waveguide (SIW) bandpass filter, which exhibits flexible characteristics, sharp roll-off, and high out-of-band rejection, making it suitable for 5G applications. The filter structure is designed with a rectangular slot with a metallic cylindrical via and a narrow propagating path. The proposed design creates a transmission zero (TZ) and shows flexibility in terms of TZ and bandwidth. This structure can be used for both inline and cross-line SIW topologies. Two filters are simulated and fabricated to validate the design. The first filter is designed at 27.12 GHz frequency with 4.98% fractional bandwidth (FBW) and one TZ at a higher stopband using an inline filter topology. The second filter is centered at 27.46 GHz frequency and 4.11% FBW with two TZ at both sides of the passband in crossline topology.