A series of compact rejection filters based on the interaction between spoof SPPs and CSRRs

Abstract

We propose a method to synthesize several band-rejection filters by etching split-ring resonators (SRRs) on the transmission line for spoof surface plasmon polaritons (SPPs), which is made of double-side or single-side corrugated metal strips. From dispersion relations, the corrugated strips can support spoof SPP modes when the operating frequency is less than the cutoff frequency. The electric field component perpendicular to the strip surface of the SPP modes can excite the complementary SRRs (CSRRs), leading to resonant modes preventing the SPP propagation near the resonant frequencies. Using this principle, single-frequency rejection filters, double-frequency rejection filters, and broad band-stop filters with bandwidth of 1.5 GHz have been designed and fabricated using the single- and/or double-side corrugated strips. Both measured results and numerical simulations demonstrate the excellent filtering characteristics of all design, which are in good agreements. The isolation of all filters can be less than −20 dB, and even reach to −38 dB at rejection frequencies. The proposed rejection and stop-band filters give important potentials to develop integrated plasmonic functional devices and circuits at microwave and terahertz frequencies.

Integrated spoof plasmonic circuits

“…In order to remove harmonics in electronic devices and communication systems, the filters based on spoof SPPs are widely stud-ied, particularly the passive devices including the band-stop filters and the band-pass filters. In terms of the band-stop filter, changing the several groove structures of spoof SPP TL or utilizing the resonant metamaterials as well prevents the EM wave transmission in specific frequency ranges [59][60][61][65][66][67][68][69]. Ref.…”

“…Fig. 4 shows the structure of band-rejection filter by etching split-ring resonators (SRRs) on spoof SPP transmission line [68]. The complementary SRRs (CSRRs) lead to resonant modes and further prevent the SPP propagation.…”

Tri-Band Band-Pass Filter Based on Multi-Mode Spoof Surface Plasmon Polaritons

“…Researches have demonstrated that the upper passband cutoff frequencies of these filters can be independently adjusted by the geometrical parameters of SSPPs waveguides. In addition, in order to realize band-rejection responses for practical applications, series of band-stop filters are proposed by etching split-ring resonators (SRRs) [28] or complementary SRRs (CSRRs) [29] in the traditional SSPPs structures with corrugated strips. It differs from the bandpass filters based on the magnetic coupling between planar Goubau line and resonators [30], [31], since the resonant modes of SRRs or CSRRs are excited effectively by the electric field components of SSPPs modes perpendicular to the strip surface, leading to a stopband near the resonant frequencies.…”

Bandwidth‐controllable band‐stop filter using spoof surface plasmon polaritons

“…SSPPs possess excellent properties of stronger field confinement and enhancement capability, dispersion control capability than other planar slow wave structures, and sub‐wavelength size. Hence, it can be widely applied to many radio frequency circuits and systems, such as low‐crosstalk line, filters, power divider, antennas, sensor, and so on.…”

“…So far, many researches on ultrathin SSPPs band‐stop filter have been reported. Most of these works have utilized extra resonant structures on the center of the strip even the back of the substrate to realize the stop band, such as the split‐ring resonators or other metamaterial particles . However, these band‐stop filters cannot control the stop band spectrum or bandwidth independently.…”