Flexible and Stretchable Microwave Filter Based on Substrate Integrated Plasmonic Waveguide

In this article, we present a new strategy to realize flexible and stretchable microwave (FSM) filter based on substrate integrated plasmonic waveguide (SIPW). To maintain the radio frequency (RF) performance under deformation, we developed lamp-strip-shaped spoof surface plasmon polariton (SSPP) units by adopting a strategy of shape preserving and combining them with serpentine interconnections through the "island-bridge" mechanism. The SSPP structure is etched on the upper surface of the serpentine patterned substrate integrated waveguide (SIW) assembled with elastic material to achieve the bandpass response. Meanwhile, a 2-D transmission line (TL)-based equivalent circuit model (ECM) is established to analyze the parasitic parameters of the serpentine structure caused at the RF level. The analysis and experiment verified that the introduction of the serpentine microstructure slows down the phase velocity in SIPW and therefore reduces the lateral size. In addition, owing to the unique electromagnetic (EM) transmission modes of SSPP/SIW and our special structural design, the fabricated filters cover the X-band of 8-12 GHz and maintain stable RF performance at conditions of the normal state, 180(degrees ) bending, 90(degrees ) twisting, and 120% stretching, which reveals that the proposed filter has potential applications in stretchable electronic systems.