This paper presents a novel compact low pass filter (LPF) based on spoof surface plasmon polaritons (SSPPs) with ultra-wide out-of-band suppression. The design utilizes a single-layer PCB with metal gratings in a tilted slotted stub shape on the top layer. The device size is \(0.75\lambda _g \times 0.12\lambda _g\) ( \(\lambda _g\) denotes the guided wavelength). A lumped equivalent circuit model is also provided. Simulated results demonstrate excellent passband performance and impressive ultra-wide out-of-band suppression. A fabricated prototype confirms simulation findings, showing 1.1 dB insertion loss at the center frequency, reflection coefficient below -10 dB in the passband, and over 30 dB out-of-band rejection beyond 38 GHz. The proposed compact SSPP LPF exhibits significant potential for applications in high-performance, miniaturized integrated circuits within the microwave frequency ranges.
