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

Qian Zhang,Jia Yuan Yin,Tie Jun Cui,Hao Chi Zhang,Bai Cao Pan

doi:10.1038/srep28256

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.

Highlights

In this article, we propose several band-rejection filters through etching CSRR elements on the SPP structure
Two transition sections serve as a bridge between the SPP waveguide and coplanar waveguide (CPW) for smooth conversion
The proposed band-rejection filter is illustrated in Fig. 1, containing the double-side corrugated strips, CSRRs, CPWs and two transition sections, in which the subfigures (b–e) correspond to parts A–D of the whole structure shown in Fig. 1(a), respectively

Summary

Introduction

We propose several band-rejection filters through etching CSRR elements on the SPP structure. The spoof SPP waveguide makes use of double-side or single-side corrugated strips to produce tighter electromagnetic field confinement and smaller propagating wavelength. In order to connect the measured system, coplanar waveguide (CPW) is employed to feed the SPP structures. Two transition sections serve as a bridge between the SPP waveguide and CPW for smooth conversion. SRRs are etched on the metal part of the corrugated strips, coming into being CSRRs. The electric field component perpendicular to the surface of metal can excite CSRRs for inhibiting signal propagation in the vicinity of their resonance frequency. The design method makes the model structure simpler and more compact, and the features of filtering SPP waves are significant for the follow-up developments of plasmonic integrated circuits and systems

Methods

Results

Discussion

Conclusion