A Strain-Insensitive Stretchable and Flexible Wideband Vivaldi Endfire Filtenna

A strain-insensitive stretchable wideband Vivaldi filtenna based on a serpentine-loaded substrate-integrated dual-plasmonic waveguide (S-SIDPW) is presented. By leveraging the unique electromagnetic propagation modes of the substrate-integrated waveguide (SIW) and spoof surface plasmon polaritons (SSPPs), the filtenna achieves bandpass characteristics. Dispersion curve analysis reveals that the cutoff frequency can be independently controlled by these two structures. Periodic slots are etched on the surface of the SIW to form SSPP mode and then combine them with serpentine interconnections through an “island-bridge” mechanism. Equivalent medium parameters of the S-SIW are extracted using the transmission-reflection method, demonstrating that the serpentine microstructure extends the surface current path, thereby enhancing the slow wave effect. Consequently, the transverse dimension is effectively reduced. To address the trade-off between stretchability and impedance-matching stability, an innovative activation strategy is proposed to place stretchable microstructures in deformation-insensitive regions while retaining non-stretchable features in sensitive areas. Benefiting from the unique electromagnetic transmission modes of the hybrid SSPP/SIW design and the specialized structural configuration, the fabricated stretchable filtenna shows stable RF performance in the passband (4–6 GHz) under various deformations, demonstrating the potential of the proposed filtenna for applications in stretchable electronic systems.