Effective Spoof Surface Plasmon Polariton-Enabled Independent Cutoff Frequency Control in Wideband Endfire Vivaldi Filtenna

In this work, we introduce a textured structure into the effective surface plasmon polaritons (ESPPs) in substrate-integrated waveguides (SIWs) to excite the mode of effective spoof surface plasmon polaritons (ESSPPs), which enables the independent control of cutoff frequencies. By leveraging the transmission characteristics of the ESSPPs mode, a wideband filter is devised. Compared to ESPPs filters, the effective permittivity of each layer of ESSPPs determines only one cutoff frequency, allowing independent control of passband and out-of-band. Furthermore, the filter’s skirt selectivity can be enhanced without elongating the filter, which is advantageous for achieving compactness. Theoretical analysis and simulations demonstrate the filter’s capacity for independently controllable cutoff frequencies, a consistently stable stopband, and a deep out-of-band rejection. The dispersion relationship of the ESSPPs mode is illustrated, followed by an examination of the control over cutoff frequencies. To validate our design, the filter is integrated with a Vivaldi antenna to create a filtenna. A prototype of the filtenna is produced using multilayer printed circuit boards (PCBs). Both simulated and measured results exhibit effective skirt selectivity, a uniform antenna gain within the passband (7.96–11.46 GHz), and a stable stopband (11.6–15 GHz).