Jin Jei Wu

In this work, based on the use of the concept of spoof surface plasmon polaritons (spoof SPPs), we propose a novel kind of microstrips to suppress the interference between bended parallel microstrips. This novel structure is implemented by introducing subwavelength periodic structures onto the sides of a conventional microstrip. We numerically analyze the transmission characteristics of such new microstrips. We also measure the suppression arising from crosstalk between the bended corrugated microstrip and the conventional microstrip in both frequency and time domains. Experimental results show that such transmission line structure has superb interference restraining properties. Additionally, transmission properties have been investigated using circuit model. It is found that the coupling effect between the corrugated microstrip and the conventional microstrip can be efficiently suppressed in high speed digital signal transmission application.

In this paper, we propose a new metallic cylindrical antenna at terahertz frequencies using the concept of low-frequency spoof surface plasmon polaritons (SPPs). The antenna is developed by introducing an open hollow ring (OHR) in each unit cell of the conventional periodic subwavelength corrugated metallic wire (PSCMW). The new structure is referred to as the PSCMW-OHR. The dispersion properties of PSCMWs and PSCMW-OHRs, the near-field and far-field distributions, as well as the radiation efficiencies are numerically evaluated and compared. By analyzing the numerical results, we find that there are extra new propagation modes that exist in the annular groove of the PSCMW-OHR, aside from the normal transmission modes in the PSCMW. Moreover, the dispersion line of the new SPP mode exhibits a negative slope. Surprisingly and interestingly, after passing through the light line, the propagation gets into the radiation zone, where it becomes a leaky mode with a complex-valued propagation constant. We have found that the far-field radiation of propagation in the leaky mode can lead to frequency scanning effects with a scanning angle of 22°, and the radiation efficiency can be increased to 90%, provided that the total number of the periodic unit cells is large enough.

Based on the concept of low-frequency spoof surface plasmon polaritons (spoof SPPs), a kind of leaky mode is proposed in a waveguide made of a subwavelength metal-block array with open slots. Numerical results reveal that a new transmission mode is found in the periodic subwavelength metal open blocks. This modal field is located inside the interior of a hollow block compared with that in a solid metal block array. The dispersion curve shows that such a new SPPs mode has a negative slope, crossing the light line and then going into a zone of leaky mode at higher frequencies. The leaky mode has a wider frequency bandwidth and this can lead to a radiation scanning angle of 53° together with high radiation efficiency. Based on the individual characteristics exhibited by a frequency-dependent radiation pattern for the present leaky mode, the waveguide structure can have potential applications such as frequency dividers and demultiplexers. Experimental verification of such a leaky mode at microwave has been performed and the experimental results are found to be consistent with the theoretical analysis.

We apply the concept of spoof surface plasmon polaritons (SPPs) to the design of differential microstrip lines by introducing periodic subwavelength corrugations on their edges. The dispersion relation and field distribution of those lines are analyzed numerically. And then through designing practical coupling circuits, we found that compared with conventional differential microstrip lines, the electromagnetic field can be strongly confined inside the grooves of the corrugated microstrip lines, so the crosstalk between the differential pair and the adjacent microstrip lines is greatly reduced, and the conversion from the differential signal to the common mode signal can also be effectively suppressed. The propagation length of those lines is also very long in a wide band. Moreover, the experimental results in time domain demonstrate those lines perform very well in high-speed circuit. Therefore, those novel kinds of spoof SPPs based differential microstrip lines can be widely utilized in high-density microwave circuits and guarantee signal integrity in high-speed systems.

A new kind of leaky wave antenna based on low‐frequency surface plasmon polaritons (SPPs) is proposed, which is constructed by periodic metallic blocks with an open slot on the top. Numerical analysis shows that by introducing the open slot on the metallic blocks, there will appear extra spoof SPPs modes in the band gap of metallic solid blocks. The dispersion curve of such spoof SPPs modes passes through the light line and enters into the radiation region, and consequently it can generate a frequency steering pencil‐like radiation. Experimental verification agrees with the theory.

The guiding properties of spoof surface plasmon polaritons (SPPs) in an array of hollowed‐out metallic blocks standing on a metallic surface are theoretically investigated in this study. For such spoof SPPs, there exists an additional guiding mode except for the fundamental mode and the former is closely related to hollowing out metal blocks. The dispersion band of this additional mode has a negative slope (corresponding to a group velocity) and it intersects the light line and then enters the radiation region as the frequency grows, which leads to a frequency steering pencil‐like radiation. The transmission and radiation properties of the additional mode of spoof SPPs are finally verified experimentally.

A new kind of differential microstrip lines by introducing periodic subwavelength corrugation in the edge, which is able to support low‐frequency spoof surface plasmon polaritions, is proposed. The surface current distribution of the subwavelength periodic corrugated microstrip is numerically analysed. A kind of differential to single‐ended microstrip coupling circuit is designed to investigate the ability of suppressing the crosstalk of such a subwavelength periodic corrugated differential pair. Experimental results show that such a structure can be utilised to effectively suppress crosstalk, and to reduce the transformation between differential‐mode and common‐mode signals.