Reconfigurable Microstrip Lowpass Filter based on Spoof Surface Plasmon Polariton

In this article, we proposed a microstrip lowpass filter with reconfigurable upper cutoff frequency based on reconfigurable spoof surface plasmon polariton (SSPP) unit cell. The reconfigurable SSPP unit cell is constructed by embedding varactor diodes into traditional corrugated microstrip SSPP unit cells. A planar gradient index structure is adopted to realize impedance and mode matching. To streamline the design process, the dispersion diagram of reconfigurable SSPP unit cell is predicted by using equivalent model. The proposed lowpass filter has reconfigurable upper cutoff frequency thanks to the reconfigurable nature of proposed unit cell. The simulated results demonstrate good filtering performances of proposed lowpass filter with good return loss, high out-of-band rejection and low insertion loss. The proposed microstrip lowpass filter may have great potential applications in modern communication systems.