Capacitive-coupled Series Spoof Surface Plasmon Polaritons.

Jia Yuan Yin,Jian Ren,Tie Jun Cui,Hao Chi Zhang,Qian Zhang

doi:10.1038/srep24605

Jia Yuan Yin, Jian Ren + Show 3 more

Open Access

https://doi.org/10.1038/srep24605

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Abstract

A novel method to realize stopband within the operating frequency of spoof surface plasmon polaritons (SPPs) is presented. The stopband is introduced by a new kind of capacitive-coupled series spoof SPPs. Two conventional H-shaped unit cells are proposed to construct a new unit cell, and every two new unit cells are separated by a gap with certain distance, which is designed to implement capacitive coupling. The original surface impedance matching is disturbed by the capacitive coupling, leading to the stopband during the transmission of SPPs. The proposed method is verified by both numerical simulations and experiments, and the simulated and measured results have good agreements. It is shown that the proposed structure exhibits a stopband in 9–9.5 GHz while the band-pass feature maintains in 5–9 GHz and 9.5–11 GHz. In the passband, the reflection coefficient is less than −10 dB, and the transmission loss is around 3 dB; in the stopband, the reflection coefficient is −2 dB, and the transmission coefficient is less than −30 dB. The compact size, easy fabrication and good band-pass and band-stop features make the proposed structure a promising plasmonic device in SPP communication systems.

Highlights

A novel method to realize stopband within the operating frequency of spoof surface plasmon polaritons (SPPs) is presented
We propose a capacitive-coupled series spoof SPP waveguide, in which every two H-shaped unit cells in the ultrathin corrugated metallic strip[15] are regarded as a new unit cell in this particular design
The conversion part (Part II) from coplanar waveguide (CPW) to the SPP waveguide is similar to that in ref. 15, in which the gradient groove depth varies from zero to 4 mm, to reach the broadband momentum matching, and the optimized curve of flaring ground is described as an exponential function (y = C1eαx + C2, α = 0.1, where C1 and C2 are determined by the length of the Part II and the width of the flaring ground) for impedance matching simultaneously

Summary

Introduction

A novel method to realize stopband within the operating frequency of spoof surface plasmon polaritons (SPPs) is presented. Combining the SPP transmission line with substrate integrated waveguide (SIW), another approach has been presented[29] to realize the band-pass filters by using the low-pass feature of spoof SPP waveguide together with the high-pass feature of SIW. Such two kinds of filters need additional structures to control the frequency-selective characteristics, making bulky volumes. Compared with the existing SPP filters, the proposed structure is very compact without any additional components, is easy for fabrication, and has good performance of band-pass and band-stop characteristics, which are important to the plasmonic integrated circuits and communication systems

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Results

Conclusion