Multiband Bandpass Filters Using Integrated Spurline Rectangular SSPPs

In this paper, a novel rectangular spoof surface plasmon polaritons (SSPPs) unit integrating spurline is proposed, and an in-depth analysis of its dispersion characteristics is conducted. Research results indicate that by loading a spurline onto the rectangular SSPPs unit, transmission zeros (TZs) can be introduced at its first high-order mode (Mode 1), thereby effectively generating stopband. More importantly, the proposed unit allows for precise control over the stopband position by adjusting the parameters of the spurline. Based on this principle, a dual-band bandpass filter (BPF) with a controllable stopband position has been successfully designed. To further verify the scalability of this design method, the another new rectangular SSPPs unit was constructed by etching a pair of asymmetric spurlines with different physical dimensions, achieving two independent stopbands at its Mode 1. Finally, a tri-band BPF was successfully designed and fabricated, strongly demonstrating the feasibility and scalability of the proposed structure and design method for realizing multiband BPFs.