A Compact Single-Layer Dual-Band SIW Bandpass Filter With Intrinsic WLAN Rejection

This letter presents a compact, planar dual-wideband substrate-integrated waveguide (SIW) bandpass filter for 5G and emerging 6G applications. The proposed single-layer design integrates etched slots, meander-line resonators (MLRs), split-ring resonators (SRRs), and open stubs to realize two wide passbands at 2.7?4.8 GHz and 6.3?9.1 GHz, with fractional bandwidths of 56% and 36%, respectively. An intrinsic rejection notch in the frequency range of 5.15?5.9 GHz effectively suppresses WLAN interference, while improving upper-stopband attenuation beyond 9.5 GHz ensures strong isolation from adjacent X-band signals. The fabricated prototype exhibits insertion loss below 1 dB, good impedance matching, and power-independent attenuation. The proposed filter combines wide bandwidth, high selectivity, and a compact single-layer structure, making it suitable for integrated multi-band RF front ends.