A Dual-Wideband Bandpass Filter With Independently Designed Cutoff Frequencies

We present a novel method for designing a dual-wideband bandpass filter (BPF) with independently adjustable cutoff frequencies. This approach offers potential applications in the microwave to millimeter-wave frequency ranges. Our strategy involves integrating the textured structures into the surface plasmon polariton (SPP)-like waves induced by the structural dispersion of the substrate-integrated waveguide (SIW), thereby exciting the effective spoof SPPs (ESSPPs) mode. By exploiting the transmission properties of the ESSPPs mode, we develop a dual-wideband BPF. The filter comprises five layers of SIW, each layer characterized by its width and the dielectric material it contains, allowing for versatile control over geometrical parameters and dielectric materials. This flexibility enables precise positioning of passbands within the spectrum. A prototype of the dual-wide BPF is fabricated using multilayer printed circuit boards (PCBs). Both simulated and experimental results demonstrate satisfactory skirt selectivity within the passband (4.8–6.5 GHz and 7–9.8 GHz) and stable stopband (6.5–7 GHz and 9.8–12 GHz). In addition, the filter exhibits outstanding in-band characteristics and selectivity, as verified by measurements. Furthermore, this dual-band BPF design can be readily extended to tri-band or quad-band BPFs by incorporating additional layers.