ABSTRACT In this letter, a spoof surface plasmon polariton (SSPPs)‐based filter, which can be tuned between low‐pass and band‐pass function is proposed. The low‐pass characteristic is generated by the periodic structure of SSPPs. Meanwhile, the band‐pass function is achieved by introducing metal vias in the SSPPs unit cells. PIN diodes and bias circuits are used to control the switching between low‐pass and band‐pass performance. The equivalent circuit model is established by transmission line t